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88SN0062 ~er~e-~~r-X988-6g6 3~~y-~9;-}988-6P6 July 27, 1988 BS REQUEST ANALYSIS AND RECOMMENDATION 88SN0062 Contel Cellular, Inc. Midlothian Magisterial District East line of North Providence Road REQUEST: Conditional Use Planned Development to permit a 198 foot communica- tions tower in a Community Business (B-2) District. A sixty-eight (68) foot exception to the eighty-one (81) foot rear yard setback requirement for the 198 foot tower and a ten (10) foot exception to the thirty (30) foot rear yard setback for an associated equipment building are also requested. PLANNING COMMISSION RECOMMENDATION RECOMMEND DENIAL. STAFF RECOMMENDATION Recommend approval for the following reasons: A. The subject property is currently zoned Community Business (B-2) and as such could be developed for a variety of commercial uses. In addition, adjacent properties are zoned commercially and have been developed for commercial uses. The proposed tower will not generate excessive traffic or noise and will have minimal impact upon area development. B. Similar communications towers have been erected in the area without any apparent adverse impact upon adjacent commercial properties. C. The conditions recommended herein will further minimize the pos- sibility of any adverse impact upon area development, the Chesterfield County Public Safety Trunked System, or the County Airport. (NOTE: THE CONDITIONS NOTED WITH "STAFF/CPC" WERE AGREED UPON BY BOTH STAFF AND THE COMMISSION. CONDITIONS WITH ONLY A "STAFF" ARE RECOMMENDED SOLELY BY STAFF. CONDITIONS WITH ONLY A "CPC" ARE ADDITIONAL CONDITIONS RECOMMENDED BY THE PLANNING COMMISSION.) CONDITIONS (STAFF) 1. The plan prepared by Potts and Minter, dated March 14, 1988, shall be considered the Master Plan. (P) (STAFF) 2. This Conditional Use Planned Development shall be granted for the purpose of constructing a 198 foot tower and an equipment building. (P) (STAFF) 3. All driveways and parking areas shall be graveled and main- tained to minimize dust problems and provide ease of ingress and egress. (P) (STAFF) 4. There shall be no signs permitted to identify this use. (P) (STAFF) 5. The base of the tower shall be enclosed by a six (6) foot high fence, designed to preclude trespassing. The fence shall be placed so as to provide sufficient room between the fence and property line to accommodate evergreen planting having an initial height and spacing to provide screening of the base of the tower and the equipment building from adjacent properties. Further, existing vegetation located between the fence and the property lines shall be retained, where possible, to provide further screening of the base of the tower. A detailed plan depicting this requirement shall be submitted to the Planning Department for approval in conjunction with final site plan review. (P) (STAFF) 6. Prior to release of a building permit for the tower, a copy of FAA approval shall be submitted to the Planning Department. (P) (STAFF) 7. The tower and equipment shall be designed and installed so as not to interfere with the Chesterfield County Public Safety Trunked System. Prior to release of a building permit, the applicants shall perform an engineering study to determine the possibility of radio frequency interference with the County system and the study shall be submitted to the Chesterfield County's Communications and Electronics staff for review and approval. (FD) (STAFF) 8. The developer shall be responsible for correcting any frequency problems which affect the Chesterfield County Public Safety Trunked System. Such corrections shall be made immediately upon notification of any problems by the Chesterfield County Communications and Electronics staff. (FD) (STAFF) 9. Prior to the issuance of a building permit, thirty-five (35) feet of right of way, measured from the centerline of North Providence Road, shall be dedicated to and for the County of Chesterfield, free and unrestricted. (T) (STAFF) 10. In conjunction with the Commission shall grant Plan. (P) approval of this request, the Planning schematic plan approval of the Master 2 "~$N0062/BSJUL$/JULY27U GENERAL INFORMATION Location: East line of North Providence Road, approx- imately 200 feet north of Midlothian Turn- pike. Tax Map 18-15 (1) Parcel 15 (Sheet 8). Existing Zoning: B-2 Size: 0.4 acres Existing Land Use: Vacant Adjacent Zoning & Land Use: North - B-2; Commercial South - B-2; Commercial East - B-3; Commercial West - B-2 and B-2 with Conditional Use Planned Development; Commercial Utilities: Public water and sewer not required for proposed use. Environmental Engineering: Drains through easements to tributaries of Pocoshock Creek. There are existing off- site drainage problems downstream at Cloverleaf Lake Apartments, which experi- ences occasional flooding. The proposed improvements will generate low runoff and will not adversely affect surrounding properties. No on- or off-site drainage and/or erosion control problems anticipated with this development. Fire Service: Buford Fire Station, Company 4~9. At pre- sent, fire service capability adequate. General Plan (Northern Area Land Use and Transporta- tion Plan): General commercial Transportation: Proposed use will have minimal impact on area traffic patterns. The Northern Area Land Use and Transportation Plan identifies North Providence Road as a collector with a recommended right of way width of seventy (70) feet. Right of way should be dedicat- ed in accordance with the Plan. DISCUSSION A Conditional Use Planned Development is requested with the intent of erecting a 198 foot tower and equipment building. The planned facilities 3 88SN0062/BSJUL8/JULY27U will provide cellular phone communications. The facility will be visited occasionally by maintenance personnel, but otherwise will be unmanned. Exceptions to the rear yard setback requirement for the tower and associ- ated equipment building are also requested. The area surrounding the request parcel is characterized by commercial development and the Northern Area Land Use and Transportation Plan desig- nates the site for heavy commercial use. The property is currently zoned Community Business (B-2) and could be developed for those uses permitted in that District. The proposed tower will not generate traffic and noise which is usually associated with uses permitted by B-2 zoning. Through the Conditional Use Planned Development process, the Commission and Board can impose conditions that further ensure appropriate land use com- patibility with existing area commercial uses. The recommended con- ditions are designed to ensure that the facility will not adversely affect the surrounding area. (Conditions 3, 4, and 5) It should be noted that similar communications towers currently exist in the area without any apparent adverse impact upon adjacent commercial land uses. Specifically, a 100 foot tower is currently located on prop- erty fronting Buford Road to the east within 550 feet of the proposed facilities. In addition, a 430 foot tower has been erected on State Police Headquarters property fronting Midlothian Turnpike to the east. The County Airport Manager has indicated that the tower will not adverse- ly affect the County's airport operations. The Chesterfield County emergency radio personnel have reviewed this request and indicated that the proposed tower and equipment should be designed so as not to inter- fere with the Chesterfield County Public Safety Trunked System (Condition 7). Once the facility is in operation, the developer should be required to correct any problems should they arise. (Condition 8) The requested setback exceptions should not have any adverse impact upon adjacent commercial development to the north, east and south. Therefore, approval of these exceptions would be appropriate. CASE HISTORY Planning Commission Meeting (6/21/88): At the request of the applicant, the Commission deferred this case for thirty (30) days to allow the applicant an opportunity to meet with area property owners. Staff (6/22/88): The applicant was advised in writing that any new information must be submitted no later than June 27, 1988, in order to be considered at the July 19, 1988, Zoning Session. 4 ^~N0062/BSJUL8/JULY27U Staff (6/27/88): To date, no new information has been submitted. Planning Commission Meeting (7/19/88): The applicant accepted the recommendation. There was opposition present. Concerns centered around whether or not the tower would present a safety problem for area business establishments and more particularly a day care center. On motion of Mr. Kelly, seconded by Mr. Warren, the Commission recommend- ed denial of this request. AYES: Unanimous. The Board of Supervisors on Wednesday, July 27, 1988, beginning at 2:00 p.m., will take under consideration this request. 5 88SN0062/BSJUL8/JULY27U y ~ 1 OWN/TF CI7EfX ~ '' • _ R-7 Q= ,''''',~ Cc ,',,','~~~ .~ ~~ R CKCREEK PARK ~~`~ V o ~ ~~,j', ~ ` ~ ,•~• y .~ s y ~ R-TH •. ~ ~ c '9 c -~ ~ ~' ~ o ./ it ~ ~ '~~ 30' Z V '~ ~ i/i FEN ~ .~_ ~ ~, ~ ~ ~I ~ 11 BON AIR HILLS v 0 , j ~ w B-3 ~ 11 ~ 2c OP ~'Tl ~ • ';~ 2~ ~ • c ~_ , ~• ': MIDI-~~HI AN Ma''~ S, Ni...~ ~ ` ~ ,`, , ~ ~ C ~~ E V ~~~~~Er ~ + 0 PROVIDENCE GREEN ~ ~ ~ ~ _5 ~ o ~1 W i v ,.a~ r~ ~ •~ d ~ ~ e ~. ~ y R TH . c .~• ~-nni~~ ~-~ _ ~ I I i zc ~.. II ~ PENN ACRES T ~~~"' ' R _ = G PROVIDENCE COURT _ .:; U S TA N G V s i ~~~ 0 ~; n O ~~ OI I N TOIfiEf; - (HE/GHT /BS) N~'M OIO E /B/. Gt7 ' y a { 9~ 9" ~ ~ < ~-~-~ ~o ~o ~ ~ ~ ~~ ~~: ~ ! a ~ O a 0 ~ • ~~, '. . ~ ~~ ~ •. /B~i OD " EoUiP~r~" SHELTER . . ~~ ; Q. _ ~ ; ~-. ,o . •.; • .,~ 4/'x:7S X8"_~/GH ~ CHA//3'L //`Jft -FE-/YG6 ,Z~6'iY/DE GATES ~~ ~a~ <~ ,~~ ~o~ ~^. ~ ~o~. 3 ~` a~ ~~ `~ I~ ~-. 885/~[OO~'2-/ i J. LLOYD CUMBHY, D.D., LTD. 2701 TURNER ROAD RICHMOND, VIRGINIA 23224 T~-EptiONE 276-8578 July 26, 1988 ~}~.~ R. p. Sowers Jr. Patient First 8110 rTidlothian ~rnpike Pichrnond, Va. 23235 Dear Sir: Reference is made to your inquiry concerning the tower which is installed adjacent to my property at 2701 Turner Ppd. _ I can certainly understand your opposition to a 198 foot tower in your area. Even though the one adjacent to me is partially screened at ground level by trees it is still an eye sore and a detriment to the properties in the area. Very truly yours J. Lloyd ~umbey S L ROBERT S. LOVELACE CO., INC. MANUFACTURERS REPRESENTATIVE P. O. BOX 31393 RICHMOND, VIRGINIA 23294 804-747-6030 Pete Sowers July 27. 1988 Patient First Corporation 15 East Franklin Street Richmond, VA 23219 Re: Lightning induced power line disturbances Dear Pete, The erection of a Communications tower near your health care facility makes it even more imperative that you protect all electronic equipment with the proper surge suppression and transient elimination which provides both common mode (line to ground) and normal mode (line to neutral) noise attenuation. L.E.A.-Dynatech's Kleanline filters and TE products provide the finest protection of this sort available. I have included technical papers by Roy Carpenter which support your concern about lightning induced transients in facilities near radio and telecommunications towers. According to Peter Carpenter, Roy Carpenter's son and engineer at Lightning Eliminators and Consultants, .Inc., Santa Fe Springs, CA., "near" means anything within a quarter mile radius of the tower, and that the nearer the point of the lightning strike (the tower), the more severe we can expect the effects to be. I hope this information is helpful to you in your planning. If you.. require any further information, please don't hesitate to call. Sincerely, ROBERT S. LOVELACE CO., INC. Dick Schini Sales Engineer 13007 Lakeland Road Santa Fe Springs, California 90670 (213)946-6886 PROTECTED FACILITIES LISTING Type of Facility Number Protected AM Radio Braodcasters 20 FM Broadcasters 18 TV Broadcasters 20 Petroleum Storage 41 Petroleum Products Processors 11 Meterological Data Sites 44 Chlorine Plants 2 Corporate Buildings 13 Computer Centers 5 Communications Facilities 10 Parking Lots 2 Amusement Park 1 Power Generating Plants (Nuclear & Fossil) 6 Space Tracking Stations 4 Launch Complex 1 Substations 3 Energy Control Centers 6 Microwave Sites 8 Transmission Lines (3 sites) 15 Miles Cooling Towers 32 TV Cable Repeaters 4 Hospital Complex 2 ,~ Type of Facility Explosives Test Sites Aircraft Parking Terminals Airport Control Tower Nuclear Platns Oil Reservoir Gas Plants Earth Stations Test Facilities (Rocket Sled) Aircraft Hangers Air Force Tracking Centers Waste Processing Plant Asphalt Plant Convention Center Amusement Park Building Number Protected 2 40+ 1 2 2 2 4 4 4 6 2 1 1 1 c ti LIGHTNING ELIMINATORS AND CONSULTANTS INC. Dissipation Arrays Sales I{istory 1972 - 1986 -------------------------- Customer -------- Location -------- Date ---- Description ----------- KHOF - TV California 12/71 TV Station Transmitter Site Elgin AFB Florida 5/73 ~ 1200 ft. Comm. Tower Unocal-Union Oil Indonesia 4/83 4 20 Acre Tank Farm CKLW Windsor, Ontario 5/73 5 Tower AM Station NASA-STDN Rosman, NC 9/75 400 Acres Ant. &' Comp. Warner Cable Harrisonburg, VA 9/73 TV Transponder Site Florida Power Orlando, FL 11/73 Meterology Tower Site WED Enterprises Orlando, FL 01/74 100 Acre Parking Lot gin AFB Florida 03/74 Rocket Test Site Jersey Power & New Jersey 04/74 Neterology Tower Site Light Walt Disneyworld Florida 06/74 Large Building PEPCO Oyster Creek, NJ 05/74 Meterology Tower Site Science Assoc. Rochester 06/74 Meterology Tower Site Kennedy Space Ctr .Florida 07/74 Meterology Tower Site NASA-STDN Cape Kennedy, FL 02/75 Space Tracking Base Stn. WKBN Radio Akron, Ohio 08/74 4 Tower AM Site WSB Radio Atlanta, GA 08/74 600 ft. AM Tower Penn Power Reading, PA 09/74 Meterology Tower Site WINZ Radio Miami, FL 11/74 6 Tower AM Station Florida Power Turkey Point, FL 09/74 Meterology Tower Site Corporation Florida Power Orlando, FL 10/74 Elec. Substation corporation .imet Colorado 10/74 Meterology Tower Site ~/ -2- Customer Location Date Description Commonwealth Chicago, IL Edison Dayton Power & Dayton, Ohio Light WED Enterprises Orlando, FL Ponce Broadctg. Puerto Rico Allied General South Carolina Florida Power & Ft. Lauderdale, FL Light NASA - Launch #41 Cape Kennedy, FL WDBO - Radio Orlando, FL Carolina Power North Carolina Union Electric St. Louis, MO E. I. DuPont South Carolina v~. R. Grace Lakeland, FL Texaco/Canada Calgary, Canada NASA-STDN Madrid, Spain Storer Brdctg. Miami, FL (WGBH) Susquehanna-WQBA Pennsylvania Florida Power & Fort Pierce, FL Light Susquehanna-WKIS Orlando, FL Pappas TV - KMPH Visalia, CA WWL Radio New Orleans, LA May Broadcasting Omaha, NE (KFAB) NASA-STDN Madrid, Spain NASA-STDN Bermuda "'sting house Chicago, IL 3roadcasting Northern Petro- Morris, IL Chemical 10/76 Elec. Substation 10/74 Energy Control 11/74 Building, Disneyworld 12/74 FM Transmitter Site 01/75 ~ Meterology Tower 75/76 Com. Site & Substations 03/75 Lavnch Umbilical Tower 05/75 3 Tower AM Radio 05/75 Meterology Twr. Atomic Gen. 05/75 Microwave Site 06/75 2 Meterology Towers 06/75 Distribution Line 07/75 Oil Storage Site 07/75 Space Track Site 08/75 4 Tower AM Transmitter 08/75 4 Tower AM Transmitter 08/75 Meterology Tower 07/75 3 Tower AM Station 08/75 300 f t. TV Twr/8000 f t. Mtn 09/75 4 Tower AM Radio 12/75 3 Tower AM Radio 01/76 5 Mi. Transmission Line 01/76 Space Tracking Station 02/76 4 Tower AM Station 01/76 6 Cooling Towers -3- Customer LocAtion Climetronics Meterology Res. NASA F1 orida Power & Light Continental Electronics South Carolina Elec. & Gas Co. Florida Power WBBH - TV Ft. Myers, FL KAYK - FM Provo, Utah WFPG Radio Atlantic City, GA Fluor Corp.(PPG) Chlorine Plant, LA 'GM Radio Richmond Hill, Ontario, Canada Gulf Power Corp. Pensacola, FL Phila. Electric Philadelphia, PA TRC Wethersfield, CT WLIF Radio Chicago, IL Robstone Company Miami, FL Home Cable Jackpot, NV Conalco Revere Hannible, Ohio Sandia Labs Albuquerque, NM TRW - DSSG Adams, MA KFAB Broadctg. Omaha, NE E. I. DuPont Dumbarton, SC Florida Power & Miami, FL Light etropolitan Reading, PA F~li son Date Description 03/76 Meterology Tower Site 03/76 Meterology Tower Site 02/76 2 Meterology Towers Sites 05/76 2 Communication Towers 04/76 700 ft. AM Tower 05/76 Generating Plant 05/76 Meterology Tower 05/76 900 f t. TV Tower 07/76 FM Tower on Mountain 07/76 AM RAdio Station 08/76 Large Chemical Plant 09/76 6 Tower AM Station 09/76 4 Umbrella Arrays 11/76 Generator Station 10/76 Meterology Site 11/76 AM Radio Tower 01/77 Dade County Airport 02/77 TV Translator Site 03/77 Elec. Substation 03/77 Communications Site 03/77 Meterology Site 03/77 3 Tower AM Transmitter 05/77 7 Comm. Sites in U.S. 04/77 Meterology Site 06/77 3 Mi. Island Power Plant (Full Site) Hauppage, NY Altadena, CA Wallops Island, VA Ft. Lauderdale, FL Belgrade, Yugoslavia Eastover, SC Largo, FL -4- Customer Location Da t e Northern Morris, IL 06/77 Petrochemical MKC Properties ~ Calgary, Alberta, CAN 05/77 Sandia Labs Albuquerque, NM 06/77 Texaco of Canada Edmonton, Alberta, CAN 06/77 Hamana Hospital Louisville, KY 08/77 John Hopkins Laurel, MD 08/77 University WBBH - TV Ft. Myers, FL 08/77 Conalco Revere Hannibal, Ohio. 08/77 Vail Association Vail, CO 08/77 Sudbrink (WTOW) Philadelphia, PA 08/77 Radio Naples Naples, Italy 08/77 .,unty of San Bernardino, CA 09/77 San Bernardino Sudbrink (WLIF) Baltimore, MD 09/77 Dayton Power & Dayton, Ohio 09/77 Light U.S. Erda White Sands, NM 09/77 Sandia Labs Aiken, SC 09/77 Sandia Labs Albuquerque, NM 01/78 Ann Arbor Tran. Ann Arbor, MI 07/78 Ball Brothers 2 USA locations 07/78 Ethyl Corporation Pasadena, TX 06/78 Florida Power & Miami, FL 07/78 Light Allied-General Barnwell, SC 09/78 Blout Bros. Corp. Westlake, CA 09/78 Stabell Services Ibadan, Nigeria 10/78 Ethyl Corporation Pasadena, TX 10/78 Description 6 Cooling Towers TV Transmitter on high Mtn. Meterology Site 3 Oil Storage & Processing Plants Hospital Complex Meterology Tower Site 980 f t. TV Tower Elec.- Substation Restaurant & Lift Terminal FM Broadcast Station AM Radio Transmitter 300 ft. TV Translator 900 f t. FM Tower Meterology Tower Site Transportable Met. Tower Communications Tower Site White Sands Test Site Communication, Dispatch Ctr Meterology Towers 4 Cooling Towers System SCADA Center Processing Plant - Nuclear Waste Meterology Sites (2) Gas Plant Process Plant -5- Customer Location Date Description Llanoven S.A. Puerto, Venezuela Central Louisiana Bunkie, LA Electric Co. American Sign & Spokane, WA Indicator Blout Brothers Westlake, LA Euro-Trans- French Gugana Atlantiq. Penton-WQSR Sarasota, FL Cubic Corp. Sardinia, Italy Jackson Cable TV Jackson, MS Continental Tel Tucson, AZ Mobil Oil Beaumont, TX N.E. Utilities Connecticut Services S. Coast Guard Boston, MA KQIC-FM Durango, CO City of Atlanta Atlanta, GA Phelps Dodge Ajo, AZ Cubic Corp. Sardinia, Italy KINI - FM Indian Res., SD WK YT Lexington, KY Phillips Pet. Bartlesville, OK WTHI Terra Haute, IN So. Frvit Distr. Orlando, FL Digital Systems Stafford, TX Cloride Southern Mexico Tehuantepec KTDS ream Brdctg. Odessa, TX 11/78 Large Oil Reservoir 11/78 Communications Site 01/79 Computerized Sign 01/79 Meterology Tower Site 03/79 Aries Launch Complex (2 Sites) 03/79 980 ft. TV Tower 05/79 Radio Control Link 06/79 TY Translator ` 10/79 Microwave Tower 11/79 Refinery Area 11/79 Nuclear Gen. Plant 11/79 Microwave Tower/Transmitter 11/79 FM Transmitter on 11,000 ft Mountain 12/79 Communication Stn., City 09/79 Meterology Tower Site 04/80 Radio Control Center 04/80 FM Transmitter 06/80 FM Transmitter 07/80 Oil Storage Tanks 10/80 FM Transmitter 05/80 Communication Site 02/81 Meterology Site 04/81 Chlorine Plant 10/81 FM Transmitter 04/81 FM Transmitter -6- Customer Location Texas Pipeline Houma, LA Occidental Oil Grand Junction, CO Lower CO River Austin, Texas WRQK - WKOS Greensboro, NC Lower CO River Austin, Texas Grasis Tower Co. Tulsa, OK Canada Atomic Chalk River, Ontario Cajun Elect. Pwr. New Orleans, LA Cubic Corporation South Korea University Stn. Dayton, Ohio WVUD Martin Marietta New Orleans, LA 'NASA) .ederal Express Memphis, TN Delmarva Power Rivera Beach, MD Company Cubic Corporation South Korea University of Tampa, FL So. Florida Texaco Canada Edmonton, Alberta Rockwell Int'1 Dallas, Texas Columbia Nitrogen Augusta, GA Federal Express Colorado Springs, CO E. I. DuPont Savannah River, SC Lower CO River Austin, TX Climatronics Bohemia, NY ^ylix Memphis, TN RCA America Princeton, NJ Da t e 06/81 05/81 06/81 08/81 06/81 10/81 09/81 10/81 11/81 11/81 01/82 81/82 01/82 09/82 09/82 10/82 08/82 09/82 10/82 09/82 08/82 08/82 06/82 04/82 Description Microwave Site Shale Oil Production Site Energy Control Center 680 f t. FM Tower Energy Control Center Microwave Site Meterology Site Energy Control Ctr. Radio Control Center FM Transmitter Large Test Facility 1 Sq. Km of Airport (incl. 3 hangars & 1 Mi . of bldgs. 4 Cooling Towers Radio Control Center FM Station Oil Storage & Processing Radio Transmitter Processing Plant Computer Center Meterology Towers (7) Elec. Substation Meterology Tower Earth Station Meterology Tower -7- Customer Location Da t e WBAP Radio Fort~Worth, TX 01/82 KFSN-TV Fresno CA 03/82 Cubic Corporation US Navy, SC 09/82 WKZL - FM Winston Salem, NC 11/82 WBBH - TV Fort Myers, FL 02/83 State of Georgia Mental Hospital, GA 02/83 Pappas Telecastg. Visalia, CA 09/83 PPG Industries Lake Charles, LA 09/83 Texaco, Inc. Midland, TX 08/83 Rooney (FEC) Memphis, TN 06/83 Conoco, Inc. Lake Charles, LA 09/83 Steelcraft Memphis, TN 09/83 Federal Express Memphis, TN 07/83 Dept./Transp. Gretna, LA 07/83 Dixie Electric Baton Rouge, LA 08/83 Conoco Lake Charles, LA 05/83 Enviroplan W. Orange, NJ 06/83 TRC Hartford, CT 11/83 Public Radio Greenwell Springs, LA 11/83 Ethyl Corporation Pasadena, TX 12/13 Federal Express Memphis, TN 2/84 NIPSCO Indianapolis, IN 6/84 Delmarva Power Salisbury, MD 6/84 Federal Express Memphis, TN 7/84 Cubic Corporation Bodie Island, NC 3/84 Description 1 AM Radio Tower TV Tower Radio Control Center 500 ft. Tower 1000 f t . TV Towe r Communications Site TV Tower on 11,000 Mtn. Chemical Plant 18 Oil Storage Tanker Large Hangar Microwave Site Flight Line structure Flight Line, Aircraft Docks Communication Site Energy Control Center Microwave Site/Tower Meterology Tower• 328 ft. 180 ft. Meterology Tower 500 f t. FM Tower 9 Cooling Towers Airport East Ramp(FEC) Energy Control Ctr. (Bldg.) Microwave Site/Tower FEC Corporate Bldgs. Radio Control Network Site ~~ -8- Customer Location -------- -----'-- Cubic Corporation Thailand Federal Express Colorado Springs, CO KDNL St. Louis, MO WEVY Bonita Springs, FL Federal Express Memphis, TN Federal Express Memphis, TN Tenneco Lafayette, LA Orange Electric Orlando, FL WAFB-TV Baton Rouge, LA Cubic Corp. Thailand C & C Sales Raytown, MO Gardner-Zemke Carlsbad, NM dernreich Brdctg. Cavanal Mtn., OK Cubic Corporation Okinawa Gary Englehardt Kutztown, PA Harrison Int'1 Memphis, TN (FEC) Columbia Nitrogen Augusta, GA Gulf State Util. St. Francisville, LA Gulf State Util. Baton Rouge, LA Federal Express Memphis, TN Federal Express Memphis, TN KPOM-TV Ft. Smith, AR Phillips Petro. Bartlesville, OK H. P. Foley Co. Reading, PA GPU Corporation Reading, PA Date Description 1/84 Tracking Instrum.Subsys. 10/84 FEC Building 10/84 1151 ft. TV Tower 7/84 680 ft. TV Tower 7/84 FEC Building 8/84 FEC Building 6/84 150 ft. Microwave Tower 8/85 Water Processing Plant 7/84 500 ft. TV Tower 7/84 200 ft. Radar Tower 6/85 Building ~~ Late 85 Atomic Waste Disposal 10/84 166 ft. Tower 1/85 Radar Tower 12/84 Array for House 7/85 FEC Corporate Hq. Buildings 1/85 400 ft. Hot Gas Stack 5/85 Microwave Tower 5/85 Microwave Tower 5/85 3 Hangars - FEC Airport 5/85 Large Building on Airport 4/85 450 ft. Tower 5/85 Cooling Towers 7/85 Computer Center, Public Utility 7/85 Headquarters & Lab Bldgs. Customer Central Louisiana Electric Company WFPG - FM Department of F,nergy S. M. Electric WAVE - FM WKYT - TV KQIC - FM Union Camp University of Illinois Y7AGT - TV Northern Indiana Public Service Co. City of Lafayette WKYT - TV American University Computer Support Service Federal Express State of Louisiana WPLO Corps of Engineers -9- Location Date Boyce, LA 4/85 Atlantic City, NJ 6/85 Albuquerque, NM 6/85 Newark, NJ Sarasota, FL Maysville, KY Willmar, MN Franklin, YA 7/85 7/85 7/85 7/85 7/85 Urbana, IL Lexington, KY Highland, IN Lafayette, LA Lexington, KY Washington DC St. Joseph, MO Memphis, TN 8/85 Description 200 ft. Grasiss Tower Radio Tower Nuclear Waste Storage Site FEC Hangar FM Tower, 1000 ft. 985 ft. 'fY Tower Utility Tower 3 Mi. of 69 Kv. Transmission Line Radio Tower 10/85 T.V. Station 10/85 Energy Management Center 10/85 13 Substation Grounding Systems 10/85 T.Y. Station•Tower 10/85 Media Transmitter Site 10/85 Asphalt Plant 10/85 Baton Rouge, LA 11/85 Atlanta, GA 12/85 Alburquerque, NM 12/85 Super-Hub Ramp Expansion Radio Tower Radio Tower Towers/Buildings Equipment -l.(~- Phillips Petroleum Brevard County State of Louisiana Florida Power and Light WPL P - AM Union Camp Mill Federal Express Complex Commonwealth Edison City of Colorado Springs Phillips Petroleum City of Lafayette, Louisiana CLECO Building Northern Indiana Public Service Co. Bartlesville, OK 1/86 Storaye Tanks Titusville, FL 3/86 Communication Tower Metairie, LA 5/86 Mississippi River Bridge Site Miami, FL 6/86 Communications Site t4iami , FL 7/86 6-400f t. Radio Towers Eastover, SC 8/$6 Paper Mill Memphis, TN 8/86 Super-flub Byron, IL 8/86 Nuclear Plant Colorado Springs, 8/86 Systems Energy CO Control Old Ocean, 7.'X 8/86 Storage Tanks 260' Tower Lafayette, LA 9/86 Microwave System/& Energy Management System , Pineville, I.A 9/86 Energy Management ' Center Ifammdnd, IN 10/86 Microwave Site r ,, . ., ~G ~ ~ I ~ ~3 LINE VOLTAGE ANOMALIES AND OPTIMIZED SOLUTIONS Roy B. Carpenter, Jr. APRIL 1983 Report No. LEA-83-1 ~~ 1~ ~ V 12516 LAKELAND ROAD, SANTA FE SPRINGS, CA 90670 TABLE OF CONTENTS INTRODUCTION Background Scope and Objectives Definition of Terms or Types of Anomalies THE LINE VOLTAGE ANOMALY PROBLEM The Destructive Phenomena Man-Made Disturbances or Hazards Disruptive Transients Disruptive Power Anomalies Over-Voltage and Under-Voltage Situations THE POWER LINES PROTECTION REQUIREMENT For Protection Against Potentially Destructive Anomalies For Protection Against Potentially Disruptive Anomalies For Protection Against Primary Power System Anomalies The Relative Risk Factor PROTECTION AGAINST DESTRUCTIVE ANOMALIES Concepts and Considerations C The Parallel Protector Concept The Series Hybrid Protector PROTECTION AGAINST DISRUPTIVE ANOMALIES Concepts and Considerations The Hybrid Filter Concept PROTECTION CONCEPTS FOR DISRUPTIVE VOLTAGE LEVELS Concepts and Considerations The Perfect Power Source SUMMARY OF PROTECTION RECOMMENDATIONS BIBLIOGRAPHY l -i- LIST OF FIGURES Figure 1, Line Voltage Anomalies, Page 3. Figure 2, Sample Surge Voltage as a Function of Distance from Stroke to Line, Page 6. Figure 3, Vertical Lightning, Cloud-to-Ground and Figure 4, Horizontal Lightning, Cloud-to-Cloud, Page 8. Figure 5, Atmospheric Transients and Figure 6, Earth Current Transients, Page 9. Figure 7, Some Earth Current Transients and Figure 8, Electromagnetic Field Induced Transients, Page 11. Figure 9, Combined Transient Recording Data (IEEE), Page 12. Figure 10, The Parallel Protector and Figure 11, The Series Hybrid Concept, Page 20. Figure 12, The LEA Surge Eliminator Concept, Page 22. Figure 13, Surge Eliminator Protective Action, Page 23. Figure 14, Kleanline Filtering Systems, MB Series and Figure 15, Kleanline Performance, Page 28. Figure 16, The Perfect Power Source and Figure 17, Regulation Concept, Perfect Power Source, Page 32. LIST OF TABLES Table 1, The Power Mains Environment, Page 3. Table 2, Potentially Destructive Power Mains Anomalies, Page 4. Table 3, Significant Lightning Stroke Characteristics, Page 6. Table 4, Summary of Risk Factors, Page 18. Table 5, Comparison of Performance Capabilities, Page 27. Table 6, Comparison of Regulator Performance, Page 31. Table 7, Selecting the Protector, Page 33. Table 8, Regulator Performance Comparison, Page 33. C -ii- INTRODUCTION Background The recent progress in electronic systems has brought with it an increased sensitivity to the operating environment. One aspect of that environment, the source of power, is also a source of destructive, disruptive and reliability-deterrent voltage anomalies. For more than eleven years Lightning Elimination Associates, Inc. (LEA) has been working in the field of protection systems. One result has been a natural evolution of protective products that match the industry requirements as they have evolved. Of course, tantamount to developing the appropriate product is defining the requirements governing protector performance. Preparing a compre- hensive definition of those requirements is as much a part of the protection task as the design of the protectors. Scope and Objectives Voltage anomalies can enter a system via the power line or the data, control or other electrical connection(s) to the system. This. paper deals only with the potential power source problems. Other papers (1)(Z) deal with the other facets of overall systems pro- tection. Table 1 presents a summary of potential power line anomalies and their sources. Power source problems can be classified into two major catagories; voltage.~~anomalses or complete-loss of power. Complete loss of power for a significant portion of a cycle~is beyond the scope of this paper and will be treated in a subsequent paper. This paper deals with those phenomena, herein termed voltage anomalies, and in other papers referred to as transients, disturbances and/or interference phenomena. These anomalous events can be further classified as either destructive or disruptive; both are considered in detail herein. This paper will provide a definition of the source of these anomalies, derive the resulting specific protection requirements (define the system power threat), identify the available protective concepts marketed today, evaluate them against the known require- ments, and present the best available solution to protect against each threat or to protect against the total as a single requirement. Definition of Terms or Types of Anomalies Anomalies are defined as parameter variations appearing on or otherwise changing the character of the sine wave from the standard established by the appropriate national electrical code. This includes both voltage and frequency deviations. -1- Voltage anomalies tend to distort the wave form as illustrated by Figure 1. Although there are basically three forms of wave form distortions (surges, noise and RFI), there are other types of anomalous events that can be destructive and disruptive. These include over-voltages, under-voltages (brownout) and single phasing. Where both neutral and a ground are carried through the system many of these anomalies can appear in common mode and transverse mode, i.e., between line (hot) and ground and/or between line and neutral, respectively. Following is a list of these anomali~ each. The definitions are not meant define the scope of the phenomena as An fiver-volts a is a condition where to we a ove the normal RMS voltage for a period in excess of one cycle. es with a short definition of to be rigorous, but rather to used within this paper. the line voltage is elevated and sustained above that level An;under-volts a is a reduction in the RMS line voltage to what has been termed t e "brownout" level and sustained for a period in excess of one cycle. A surge (energy surge) is a rapid increase in the flow of total energy (joules or watt-seconds) to the service entrance, but sus- tained for periods of :1:ess ~than-:one'hal£:-5cycle;-~ for example, due toylightning. Singler:.phasing is the state of a three phase power source when one p i~ ase is momentarily lost or lost for a period of ,at:~least ::one-• half cycle somewhere within the public•service system. Radio. Fz~equen :•znterfeYence `~(12F?,) is a high frequency cyclic p enomenon superimposed on t e ine frequency by some external influence or some common user. It is most often manifested in the form of a damped sinusoidal wave shape as illustrated on Figure 1. Electromagnetic Interference (EMI°) appears similar to RFI, but is cause y some externs varying magnetic field mutually coupled to the facility feeder lines. •Transients:=are random voltage pulses of relativeiyhigh magnitude, ut s orbs~uratian, usually less than about 100 microseconds. i~1oise•c vise's are similar to transients, but of lower magnitude and uration. They are not considered destructive, but may be disrup- tive to digital systems. ~Electroma• netic pulse• (EMP) is a single pulse of energy created by a magnetic pulse suc as t~iat created by ~l:~.ghtniny or a Fnu~lteart ••:burst: The magnitude can vary from insignificant to devastating. l -Atmos herscs is an electrical noise phenomenon related to atmospheric con itions`7sometimes the all-inclusive term "atmospheric electricity" is used) . It is manifested in the form of ~AQ~.i~~..~ul$~s previously defined and is caused by distant lightning activity as well as pre and post lightning atmospheric conditions. It can also be the result of corona activity from high structures and the impact of the iona- sphere field on them. -2- ~'` FIGURE 1 Line Voltage Anomalies Surpet 40 KV Noise Spike Below Clamp Levu ----------- RFI TABLE 1 THE POWER MAINS ENVIRONMENT POTENTIAL CAUSES POTENTIAL ANOMALIES LIGHTNING ATMOS- PHERICS LOAD SWITCHING SHOP AND FIELD EQUIPMENT OFFICE EQUIPMENT PUBLIC UTILITY AUTO- MOBILES HIGH EXPLOSION OVERVOLTAGE X X y / ~ UNDERVOLTAGE X V scrR~s X X X X SINGLE PHASING X X ~'I X X X X X EMI X X INDUCED TRANSIENTS X X NOISE X X X EMP X X -3- THE LINE VOLTAGE ANOMALY PROBLEM The Destructive Phenomena Table 2 subdivides destructive anomalous voltage events into natural and man-made causes and lists the most common potential sources. Lightning is a primary source of natural destructive anomalies. The lightning risk factor is related to the isoker- aunic number for the area of concern, the character and location of the facility to be protected (the exposure factor) and the probability factors related to the lightning stroke itself. TABLE 2 POTENTIALLY DESTRUCTIVE POWER MAINS ANOMALIES NATURAL CAUSES MAN-MADE CAUSES CLOUD-TO- CLOUD-TO- ACCIDENTS POTENTIAL GROUND CLOUD PUBLIC OTHER OWN AND ANOMALY LIGHTNING LIGHTNING TORNADOS UTILITY CUSTOMERS PLANT EXPLOSIONS oVER- X X VOLTAGES UNDER- X X VOLTAGES suRGES X X X TRANSIENTS X X X X X X EMP X X X SINGLE X X X PHASING The isokeraunic number~;(numbervof lightning; days per year) can vary from a low of near zero for the artic regions to a high of over 265 for some equatorial regions. While the maximum for the U.S.A. is 100 for central Florida, the average is about 35. Specific values for a given area can be obtained from a World Meteorological Society publication ~3~. The isokeraunic number can be used to estimate the probability of lightning for a given day (if seasons are disregarded) and the number of strikes that may be expected to terminate in any given area for that year. In applying these data two factors must be -4- considered in concert. First, the number is an estimator only and the actual value can vary considerably, and, of more significance is the fact that it only takes one strike to cause irreparable damage to electronic systems. In general, lightning results in three specific, but different, forms of hazard, direct strikes producing power or energy surges, induced transients from nearby strikes, and the EMP from the strike's magnetic field. A direct strike to any or all phase conductors near or at some distance from the facility will create a power surge. The character of this surge is therefore directly related to the character of the lightning strike, the line it strikes and the distance to the point of concern. To define the character we must look at specific cases or parameterize the character relation- ships. The factors of significance include stroke rise time, stroke peak current, distance between strokes and the facility or the resulting line impedance and the grounding resistances at significant points in between. One significant factor is shown by Figure 2, where the surge voltage is estimated for an average lightning strike for various distances from the station of concern. These numbers must be greatly increased for higher energy strokes. Some measurements indicate that these voltages could achieve levels in excess of 100 Kv if the wire insulation would support that potential without arcing, and if the measurement point was near the stroke. The higher voltages seem to be the norm rather than the exception for communications sites, FM and TV transmitters at remote mountain-top sites. Table 3 presents a summary of the range of pertinent parameters which were taken from many sources and represent a compilation of many works~4-8). The shape of typical lightning stroke current is such that it rises rapidly to its peak and then tapers off relatively slowly following a log-normal shaped curve. There are two classes of lightning strokes; the impulsive stroke and the non-impulsive or hot stroke. This characteristic determines the damage caused. The impulsive stroke is the one that ;creates most of the damage to electronic systems since it embodies a large percentage of high frequency energy. The .,rate of rise exceeds 10,000 amperes per microsecond_~and•can achieve rates of over 100,000 amperes per micro- second. An impulsive stroke usually lasts for no more than 100 microseconds. The non-impulsive or•hot stroke rises•much.slower. than the impulsive stroke, as slowly as 500 amperes per microsecond. However, it usually lasts much longer, extending out to as long as 10 milli- seconds to the 50 percentile. This type of stroke is responsible for many fires and explosions. Induced transients are the second order effects of lightning activity in or near the area of concern. Their character is related to the -5- TABLE 3 SIGNIFICANT LIGHTNING STROKE CHARACTERISTICS / Charge Range - 2 to 200 Coulombs Peak Currents - 2,000 to 400,000 Amperes Rise Time to 90$ - 300 Nanoseconds to 10 Microseconds Duration to 50$ - 100 Microseconds to 10 Milliseconds potential Energy at 99$ - 1010 Joules* *Only a small portion is manifested in a surge, usually less than 10,000 Joules. 2400 2000 1600 u a a~ 1200 ~ Mile fr ~1 M' Station a from Sta ion • .2 Miles f om Station -6- 0 1 2 3 4 ~ ~ Figure 2, Sample Surge Voltage as a Function of Distance from Stroke to Line lightning discharge and the system character into which the tran- sient is induced. In general they are high voltage, low energy disturbances. Estimates of the potential for this phenomenon range up to 100 Kv (this value is more dependent on the system circuit parameters than lightning). Installation breakdown levels usually limit the peak voltages to much lower levels, except on primary feeders. Public utilities have found that this phenomenon accounts for most of the lightning faults on lines with a potential of 20 Kv and lower. Lines as short at 50 feet can pick up a significant transient, depending on their proximity to the stroke(9). Induced transients tend to take a shape related to the first differential of the stroke itself; short, negative and/or positive going high voltage pulses of lower energy, but often destructive potential. Induced transients are created by one of three different, but related phenomena. They are the result of the invisible, but highly potent electrostatic field found between the charged clouds and the earth. This field moves and varies in strength with the charged cloud activity. Cloud-to-earth strikes create the situation shown in Figure 3; cloud-to-cloud strikes create the situation shown in Figure 4. Atmos herically induced transients are created by sudden variations in t e electrostatic potentials-the atmosphere. Where the clear air electrostatic field may be 150 volts per meter elevation above earth, during an electrical storm this field can achieve levels of up to 30,000 volts per meter of elevation. A lightning discharge to earth or another cloud will cause this field to collapse, leaving a bound charge on any conductor within its influence. The resulting charge seeks ground through any available path, even jumping large insulators in the way. This creates a voltage pulse that can exceed 100,000 volts. Transients resulting from electrostatic field changes are propagated over long distances. As one specific, an average energy, cloud-to-cloud discharge or a strike to earth one mile away will induce as much as 70 volts per meter of exposed wire into a thus connected system (see Figure 5). Earth current induced transients are created by lightning strikes to t e eart at or near t e acility of concern. With the termina- tion of a stroke to earth all the charge induced into the earth by that cloud must move from the point where it was induced to the point of impact of the stroke (see Figure 6), and thereby neutralize the charge. As a result of this motion of the induced charge, earth currents are set up within the earth's crust near thesurface. Any good conductors buried in the earth within the c arge area will provide a preferred path for these earth currents and thus be the recipient of these severe earth currents. The results are induced transients within the conductor directly related to the earth current character. Current along the sheath of wires will induce transients into the inner conductors through mutual induction or these currents will be superimposed on the conductors without sheaths. -7- C'7GURE 3 Vertical Lightning, Cloud -To -Ground ~ -_ - - - - ..fir = ~ - ~-^ - - -- - - - - i STROKE CURRENT ~^ _'Y~ + + l +++ +++ j _- + - _ + + + + + - + GROUND CURRENT GROUND CURRENT (Distributed) (Distributed) FIGURE 4 Horizontal Lightning, Cloud - To -Cloud STROKE CURRENT + + + + + + + + + + + + + + + + + + ~ + + + + GROUND CURRENT l -s- ~/ ''~ I'IGURE 5 Atmospheric Transients I ~~ ~- ( I I ~ ~ ~ I I I I ELECTROSTATIC ---I NEARBY I ~ I STRIKE I ~. I I FIELD I I I ~ I I I ' o~~O~D o~0 p0~~ ~ ~ SUSPENDED • INTER-PLANT • POWER LINE DATA LINES • Will experience induced transients -- %~ FIGURE 6 ,.. -~' Earth Current Transients ~i ~~ rG~^ • + + + + ++ oo~t7p0~ O~ + + + + + + ~°o^ O~~ + EARTH CURRENT ~_ BURIED + + TRANSIENTS + + + LINES • + / -9- Figure 7 illustrates two other forms of earth current transient effects. The results on the connected system are the same regard- less of the cause. Electromagnetic field induced transients are also created by lig tning disc arges. For this phenomenon the lightning flash channel acts as a large vertical radiator or antenna. The large, rapid flow of current down the ionized lightning flash channel sets up a rapidly changing electromagnetic field propagating out from the stroke channel in much the same fashion as AM broadcasting stations and is the cause of static in a radio receiver, reflected waves in the 'transmitters and transients in nearby conductors as shown by Figure 8. Generally, cloud-to-cloud strokes produce pre- dominantly horizontally polarized waves while the cloud-to-earth strokes produce vertically polarized waves. The di/dt's often exceed 100,000 amperes per microsecond. Tornados create a indT used transients generator. This within the eye of rotates the induc of rotation of th to electronic svs cyclic var are of a phenomenon the twiste ed voltage e twister. terns if the tmospheric a poor s a charge motion. with and entials c near an a field; the awtooth separation As the twister at the frequency an be damaging rea of concern. To protect against all of these destructive forms of induced transients, regardless of their cause, the protective equipment must be designed to satisfy the worst case situation, i.e., at least 99 out of 100 possible events. The protective requirements include the following: Transient Energy - 500 Joules Transient Peak Current - 20,000 Amperes Transient Peak Voltage - 6,000 Volts Transient Rise Time - 50 Nanoseconds IEE Standard 587-1980 presents a summary of findings from several sources. Figure 9 presents a composite of pertinent transient data as recorded by the different investigators. Man-Made Disturbances or Hazards Man-made disturbances come from the electrical system's environment as created by man. Again, these disturbances can be the result of a directly injected phenomenon or an externally induced phenomenon. It is futile to attempt to define all the potential causes, but the following identifies and deals with some of the more significant possibilities. Man-made disturbances may be subdivided into those caused by electromagnetic or electrostatic fields and those caused by some form of "accident". iation in the a shape similar to is the result of r and its rotary rises and falls The induced pot twister passes -10- FIGURE 7 Some Earth Current Transients - - COUPLING VIA: (1) IR DROPS (2) MAGNETIC FIELD -_~ ~~~~ ~ ~•^\ ` 1 ~/ V ~i ~ ~ - ~/ EARTH CURRENTS / FIGURE 8 Electromagnetic Field Induced Transients ... ~.,,~ r-~-..-~ ELECTROMAGNETIC FIELD (EMP) 10~.._---- 1 t= ~~, ., '' ,. ;.:.:-. -ii- FIGURE 9 Combined Transient Recording Data (IEEE 105 104 RURAL OC 103 ~ } 102- _ D: a 10~ w 1 ~ 10•t N 10.2 10.3 0.2 0.5 1 2 5 SURGE CREST KV 10 20 -12- HIGH EXPOSURE MEDIUM EXPOSURE SPARKOVER OF CLEARANCES LOW EXPOSURE a Man-made electromagnetic field transients are usually created by poor installation practices or inflexibility in the plant layout. For example, the power lines for large motors and power lines for sensitive electronics are laid side-by-side in the same cable tray or raceway. During the planning stages for a plant, it should be understood that power lines carrying any large loads will also carry and/or create transients on those lines as well as lines nearby. Electric motors with poor commutators will radiate transients into nearby lines and cause malfunctions in any electronic equipment sharing the common source of power; SCR switches, switching power supplies and the like are common offenders. Directly injected hazards are usually the result of Murphy's Law at work. The possibilities are as diverse as the industry itself. Some common examples, that have happened include: (1) High voltage wires dropping onto the lower voltage lines, arcing over them, or striking them in high winds or accidents. (2) Failure of insulation or isolation devices which inject a high voltage onto the lines. This happened three times in one year at three similar facilities separated by thousands of miles. In all three cases a related computer was destroyed. The electromagnetic pulse (EMP) resulting from a large atmospheric explosion, usually nuclear, will also create this phenomenon. The character of the EMP is usually considered similar to lightning, but with much faster rise times (nanoseconds) and much shorter duration (only a few microseconds). The energy induced into a facility can be very high if it is located near the center of the explosion, in excess of 100,000 joules. Disruptive Transients A disruptive transient is some form of voltage anomaly of less than a half cycle duration that is superimposed on the power line (mains) at a potential below the destructive level of the equipment it feeds, yet high enough to impair proper operation or significantly reduce the data or equipment reliability (mean time before failure). The causes of disruptive transients are similar to those classified as destructive, but at lower voltage levels. Specifically, they include atmospherically induced transients, earth current induced transients, EMP induced transients and all of the man-made anomalies. In addition, disruptive transients can be caused by radio frequency interference (RFI) which is created by: (1) Cross coupling between cables in the same cable tray or raceway, (2) Nearby radio, AM, FM or TV stations, radar, or -13- (3) Other types of equipment, such as motors or welders, any vary- ing high current load using the same feeder, or radiated energy from nearby equipment which is manifested in the form of elect- romagnetic or electrostatic fields. The potentials and forms of disruptive transients are related to the lines on which they are induced. Some sample forms are shown by Figure 1. Refer back to the definitions for a description. The parameters of concern are: (1) Peak noise or transient voltage which is found to vary from insignificant to values approaching the destruct level, i.e., nearly 400 volts peak-to-peak on a 120 volt RMS line and over 800 volts peak-to-peak on higher voltage lines. All are usually of very short duration, a few microseconds. (2) Radio frequency interference which usually takes the form of a damped sine wave with peak voltages as in (1) above for the first cycle and frequencies extending from harmonics of the primary power source to the very high frequency band. Disruptive Power Anomalies There are several forms of disruptive power anomalies, some of which are: A short-time loss of one or more phases is the most common fault. These incidents usually last from one to ten cycles, often with repeated on-off switching transients, and vary significantly in frequency of occurrence with the reliability of the utility servicing the area, and more significantly, with the isokeraunic number for the area. Extended outages are unusual for developed countries, but do happen, usually because "Murphy" got into the act (a drunk hits a power pole) or human errors of one sort or another. Statistics on duration of outages are about as follows: 90$ less than ten minutes 95$ less than 30 minutes 99~ less than one hour Worst case has been several days Over-Voltage and Under-Voltage Situations These conditions are the result of public utility action and/or customer overloads. Over voltates are a much less common problem and almost exclusively t e result of poor control by the utility. The statistics indicate that over voltages above 110 of the rated feeder voltage and lasting -14- over one-half cycle are almost non-existent in well developed countries. The probability is so low as to eliminate its considera- tion except possibly in some "third world" countries. However, protection against this phenomenon can be accomplished at little expense and may be worth it. Under volta es or brownouts are a very real concern in just about any part of t e wor Line voltage drops down to about 85~ of the normal rating are becoming an all too common occurrence. and are the result of customer overloads and/or the utility deliberately reducing the driving voltage to prevent overloading the generators. To properly design for extended line voltage variations the designers should plan on variations of between plus ten percent and minus twenty-five percent around the norm, at least at the secondary. level. A remote location where the consumer is at the end of a distribution line or on poorly controlled rural power is the primary area where wide variations in line voltage can be expected. -15- THE POWER LINES PROTECTION REQUIREMENT The protection requirements for systems operating off common public utility power lines can be defined by the systems` protection re- quirements and the related environmental threat. This mandates a division of these requirements into the previous classifications and results in the following: (1) For protection against potentially destructive anoT[ialies - (a) Surge energy withstand capability of at least 10,000 joules per phase* (b) Surge current withstand 160,000 amperes peak* (c) Peak voltage withstand up to 45,000 volts at service entrance and/or 6,000 volts at wall socket (d) Reaction time less than 50 nanoseconds (e) Fail-safe protection against extended over voltage *Independent of wave shape which is related to the surge energy withstand, i.e., any shape containing that energy level. These requirements are for such analogue facilities as radio ~. stations, UPS isolated conputers, motors and other more rugged electrical gear. Subdivisions within this catagory are possible if related to the specific point of concern as recommended by the IEEE (lo), (2) For protection against potentially disruptive anomalies - Protection against destructive anomalies, above, is required, plus: (f) Low energy transient voltage peaking just under the protection level, but well above the disrupt level. This varies with equipment, but may be taken as any value from about 50 volts peak to 400 volts peak-to-peak for a 120 volt RMS line or as much as 1,000 volts or more for the higher line voltages. (g) Radio frequency filtering for a band of frequencies starting at 1 KHz and extending to 100 MHz. If protection is provided against all of the other potential events, attenuation in excess of 40 db is usually not required. -16- (3) For protection against primary power system anomalies - Protection against items (1) and (2) above plus: (h) Voltage regulation to about ±5~ with input variations of from +10~ to -25$; better re ulation is not required. The fact that closer regulation can a ac ieved wit in bounds does not make it a requirement or even desirable. Regulation response time requirements are related to the protective system filter characteristics, that is, the filtering capability must eliminate variations the regulator does not respond to. For example, for a 60 Hz system, if the regulator responds to I/4 cycle or about 4 Ms the filter should be capable of filtering out all transients of lesser duration. (i) Protection against power outages or single phasing (i.e., the loss of one or more phases of a three phase power source for a significant period). This protection must take the form of a power source substitute or must protect against the impact of power loss by performing an orderly shutdown (orderly shutdown is defined as providing enough warning time to preserve data, status and/or essential functions). For many situations audible warning and complete shutdown within one to three minutes will satisfy most requirements. At this point the individual customer must define his specific requirements. Where complete loss of power cannot be tolerated for even very short periods or low probabilities, an uninterruptible power source is required. Only ten minutes of uninterrupted power is sufficient for over 90$ of the situations. The Relative Risk Factor The foregoing data is a compilation of data derived from many sources relative to these phenomena within the context. For example, given that lightning exists, what is a reasonable risk range for the pertinent perameters? Now, it is also necessary to relate the individual risk phenomenon to each other. To that end IBM sponsored a landmark study that provides the only well docu- mented details as to this relationship for computer installations. In using the data it should be recognized that the risk relation- ships are basically for urban areas and not necessarily representa- tive of the experiences at mountain-top sites, rural areas or third world countries. Table 4 presents a summary of the risk factors by catagory as IBM identified them. To deal with the differences between the urban area situation and that related with the less populated areas, consider the one factor illustrated by Figure 9. Note that as the data points are moved -17- to more rural areas the risk of exposure to higher levels of voltage transients, surge currents, etc. increases significantly. This is because there are less subscribers to share the problems. TABLE 4 Anomaly Percentage Number per Day Over-voltages, including surges 2$ (6 per year) Under-voltages 25$ 1 Outages, including single phasing 1~ (3 per year) Common mode transients* 27~ 1 Transverse mode transients* 45~ 2 *49~ of these were the damped RFI waveform These data further indicate that for the average urban U.S.A. installation a disturbing voltage anomaly of some form may be expect d on the average of more than four times per day for sensitive electronic systems. In summary, there will be disturbances; you must be prepared. -18- .. PROTECTION AGAINST DESTRUCTIVE ANOMALIES Concepts and Considerations There are numerous and diverse devices marketed as surge protec- tors. Manufacturers make similar performance claims, yet the units vary in cost, physical size and components. Their performance is seldom related to the threat and different performance parameters are often used to define their capability. It is therefore necessary to evaluate all such devices against some fixed standard that is representative of the actual threat. If compromises are made below this standard the related risk should be specifically defined so the buyer is properly informed. Of equal importance to performance parameters is the method of employment of the device within the protected system circuitry. To that end, there are two ways of implementing the protective device within the circuit. The protector. can be installed in parallel with the device to be protected as illustrated by Figure 10 or it can be installed in series with the incoming power between the source and the system to be protected as illustrated by Figure 11. The Parallel Protector Concept All of the conventional surge protectors with the possible exception of isolation transformers and LC filters are designed to be wired in parallel with the load they protect. Note: Isolation transformers and LC filters provide no lightning or surge protection and, when exposed to these anomalies, are subject to destruction themselves. An analysis of the functional circuit diagram of Figure 10 reveals deficiencies in the performance effectiveness of any parallel pro- tector, device or assembly, as follows: (1) Because it forms a parallel circuit with the protected system the "protected" must share the surge with the protector. Of course, the protector is supposed to become a very low impedance path in comparison to the protected equipment -- at just the right time. Yet it must not compromise the system performance or waste power. Two other factors further mitigate the per- formance of the parallel protector. The clamping voltage must usually be set high (several times the normal operating voltage) to prevent inadvertant operation or excessive parasitic power loss and the parallel impedance cannot be too low or it will be subject to the high energy from the driving power source. The latter problem is accentuated by low impedance sources. Also, the clamping ratio is often too high for very sensitive electronics. Ratios in the order of from five to twenty to one are not uncommon for these devices. This means that peak volt- ages of up to 4 Kv or more can be registered on a 115 V RMS line under high surge current conditions: -19- . ~ . FIGURE 10 The Parallel Protector Line Lc Is ~ Surge Curre~~~ Lc s Inductance of Connections to line. Lg a Inductance of Ground Connection. FIGURE 11 ~~ 1 The Series Hybrid Concept Service Surge Entrance Eliminator Lc EL __ Is load E~ -~-- -- Es 1s Reference Point -' -- Is =Surge Path -20- ,i ' Parallel ' --- - (a) The clamping voltage. is the peak voltage at which the (~ protector starts to limit the line voltage. {b) The clam ing ratio is the ratio of the line voltage wring surge pe c3-_.current ..vs the- initial clamping .voltage. (2) The wiring that integrates the parallel protector into the circuit becomes a series impedance to the flow of the fast rising surge currents (also shown by Figure 10). Rising current rates in the order of 100,000 amperes per microsecond are not uncommon. Under these conditions each meter of length of connecting wire may be considered about 1'~ microhenries of inductance. The result is a significant series impedance in the circuit and the voltage developed across these connections adds to the voltage across the "protected" system. In summary, the parallel protector concept is considered a compromise. The only advantage it has is ease of installation. Some of the devices in this class are. low cost, others (assemblies) are very expensive; none satisfy the total protection requirements. RThe Series Hybrid P~rotectbr The series hybrid Surge Eliminator (SE) developed by LEA, Inc. (patent pending) eliminates the series impedance influence of the ( connecting wires by separating the surge current path from the control voltage sensor as illustrated by Figure 12. The SE solves the high clamping ratio problem by using the series impedance to dissipate any over-voltage and separate it from the load. It solves the high clamping voltage problem by separating the unstable, power wasting components from the on-line control circuit. To illustrate Surge Eliminator performance consider the situation depicted by Figure 13, which presents a badly distorted sine wave for a 120 volt RMS hot-to-neutral situation where several forms of destructive voltage anomalies are shown. The equipment destruct level is assumed to be above the ±200 volts peak; normal peaks are about 166 volts. The surge protector must prevent the voltage from rising significantly above that level. To accomplish this the SE functions as followsr (1) The voltage controller assembly constantly monitors the output voltage with no significant parasitic loss. (2) When the voltage rises above the clamp voltage, usually set at 1.2 times the normal peak voltage, the voltage controller acts as a constant voltage device holding the voltage at the selected clamp level. (3) If the anomaly is more than a small transient the High Energy Dissipation Assembly is activated dissipating only the surge ._ energy like a clipper. -21- r ~ Zlri FIGURE 12 ( IN Series OUT ~ Surge Impedance I ( Switch ~ I I High I ~ Energy I ~ Switch ~ I Voltage I Controller ~ High I Energy I I Dissipator I I I ~------ - ----J Protected Equipment t__T_J Common Point Grounding _ Local Ground Matches Input Impedance Power Surge Fuse Characteristic Fully Probability <1/10 yrs. Protected w/o Interruption Time LEA Surge Eliminator Concept C C ~. -22- ~ r ~ +200 +166 0 n- structive -166 '-200 A, Before Protection ~ Note Tight Clamp +Clamp Level +16 6 --~ - - - - - - - - -- - -~--~- - - -- - 0 ~-- - - -- - - -L ~ - - - ~-- ~--- -- - -~ ~- - - - - --~ ~- ~ -166------ ------`-'' --- --------- -200 - -Clamp Level B, After Protection Figure 13,, Surge Eliminator Protective Action t -23- .. `1~ Destructive Surges PROTECTION AGAINST DISRUPTIVE ANOMALIES Concepts and Considerations Disruptive transients, as previously defined, are the largest segment of hazards presented by the power mains. The concept must protect against destructive anomalies as welleaslthe non-destructive but functionally disruptive anomalies. The for digital equipment must provide, in addition to li htnin protector tion, both RFI filtering and noise rejection such that the g Protec- voltage from either phenomenon does not exceed about f20$ ofethe normal line voltage around any point in the sine wave. Protectors marketed for this purpose are limited to some form of series type protector. No parallel device could significantly influence all of the stated problems unsubstantiated claims to the contrar yet some suppliers make protector for disruptive anomalies includehRFlofilters-LCpnetworks, isolation and so-called super-isolation transformers, and multi- stage series hybrid systems. In reviewing these potentially protective concepts, the parallel types such as encapsulated MOV's, gas tubes and zeners or transzorbs, etc., may be dismissed as obviously not effective, even though their packaging does not always make this clear. Traditionally, some form of LC filter is still used to deal with these anomalies. In review- ing contemporary RFI filter/isolation transformer concepts we finA• (1) The RFI filters provide to over 50 MHz, but no (2) only RFI filtering from about 150 KHz significant lightning protection. The isolation transformers provide filtering from about 1 KHz to 1.5 MHz, but again, no significant lightning protection. Both of these filters provide a measure of noise su the filter characteristic and/or asa result of the shieldingnconcept. Both are usually effective only against transverse mode anomalies. Common mode anomalies are often either neglected or dealt with in some limited or unorthodox manner, such as not carrying the ground wire through the filter uninterrupted. Some of the super-isolation transformers do provide both modes of filterin but the u frequency is limited to about 1.5 MHz g' PPer problems at 10 MHz, yet there are significant In summary, none of the RFI filters, isolation transformers or super-isolation transformers presently available can satisfy all the requirements for protection against both destructive and disruptive line voltage transients. LEA has therefore developed the multistage series hybrid protector called the Kleanline Electronic Filtering System to satisfy this need. -25- ,, The Hybrid Filter Concept The LEA Kleanline series hybrid concept is based on the premise that a protector must be designed to deal with all the disruptive voltage anomalies in common and transverse modesnincludi both broad band filtering and surge/over-volta e Fi ure 14 ng g illustrates-the functional logic used inrthecKleanline Filter to accomplish protection against all of the known hazards of a transitory nature as well as sustained over-voltages. Kleanline Electronic Filtering Systems they clean the power mains of all unwantedfelectrical anomaliesrfrom lightning related power surges to noise tudes and less than a microsecond durationlinsbothdcommonlandatrans- verse modes. Further, these units satisfy the CSA, UL and VDE specifications. This unusually comprehensive concept has been proven by many major firms in the data processor field as the only totally effective protector. LEA Kleanline Filters are designed around a four-stage, series hybrid concept shown on Figure 14. The first section is a Surge Eliminator which eliminates any over-voltages or power surges in excess of a voltage equal to 120 percent of the normal peak line voltage as previously described. The two series filters are stagger-tuned to provide RFI, EMI and EMP filtering across a band of frequencies ranging from 1 KHz to well over 200 MHz, providing from 35 to 40 db of filtering in both common ~ and transverse modes without introducing more than about 10 micro- amperes of leakage current to ground (earth) for the lu Refer to Figure 15 for a typical band rejection characteristicnits. The second stage removes any high voltage transients that may pass through the first stage. This voltage limiter reacts within 5 nanoseconds and will remove any form of over-voltage above clamp voltage. A final stage is included to remove the "leftovers", the low voltage noise spikes and RFI in both common and transverse modes. This function is intended to follow the sine wave and strip it at any point in the phase relationship at about ±20$ of peak voltage. As a result no significant anomaly can pass through the Kleanline Fitt-P,-_ In summary, the Kleanline Electronic Filtering hensive system of active and passive filtering significant voltage anomalies in an economical It then clips off any overshoot above the clamp provides a reasonably clean sine wave output. System is a compre- which removes the and effective manner. level and, finally, -26- ( As a matter of academic interest, Table 5 pres t performance capabilities of en s a comparison of contem orar r provide protection against E destructive and disru ti a ven a cursory comparison a form of s i p ve anomalies. t the most basic levels s h er es, multistaged all the requirements is com hybrid protector is required to satisfy l p ete protection is desired. TABLE 5 COMPARISON OF PERFORMANCE CAPABILITIES (2) Protector Makers Surge Protection ~'I Noise Rejection RFI Filters Corcom, NONE HF Aerovox, Filter Related NONE C. D. HF Filter Related NONE HF Filter Related Isolation & Topaz, Super- Deltec NONE LF(1) Filter Related , Isolation Solar NONE LF(1) Filter Related NONE Transformers LF(1) Filter Related Kleanline 'LEA, Inc. Total HF Absolute Noise Protection and Stripping LF Notes - (1) More than required to achieve some noise rejection. (2) Parallel protectors such as Transtector, GE, MOV's, TII and other gas tubes are not included as they include no RFI or noise filtering. (3) HF is high frequency RFI filtering, LF is low frequency RFI.filtering. -27- .a IN L O~ N a G 4- To Power line FIGURE 14 Kleanline Filtering Systems , M B Series Singie Phae (1.16 Ampere) iur OUT =use Surge Hph Low Trensverte Line Protector FrF11te~ Frequency Mode Filter Stripper Neutrs~ Common Noise Stripper Multiphase Surge Low High Fuse Frequency Frequency Fiber Filter High Oissipa~r Con ~ Stripper l To neutral or ground terminals on unit KieanNne Performance FIGURE 15 A M~ Ground To Protected Equipment ~o eo ~o so m to ~~ ~~i -2g » r ~ PROTECTION CONCEPTS FOR DISRUPTIVE VOLTAGE LEVELS Concepts and Considerations A disruptive voltage level has been defined as including sustained over-voltages, under-voltages (brownouts), loss of power and the related single phasing phenomenon. The concepts emplo ed to against these. voltage anomalies are very limited, including varioust types of transformer technology, various forms of switching tech- nology and some type of on-site generator or UPS. Each of these concepts have some advantages and some disadvantages; none of them alone satisfies all of the protective requirements (see Requirements De- nition). The various transformer concepts include; (1) The saturable reactor which is designed to operate under normal voltage at saturation. Over-voltages tend to over saturate the reactor and produce no appreciable increase in voltage at the secondary. Under-voltages are below saturation and therefore result in some effective increase in the transformer output. The operating range is obviously very limited, the waveform distortion is often intolerable, and they are very load sensitive. (2) The ferroresonant transformer or line conditioner is the most popular solution in use today -- basically because of lack of competition in the past. As the name implies, this device is a resonant LC network, static generator or magnetic flywheel device. Through use of a combination of L and C in various resonant and/or buck-boost winding configurations they seek to stabilize the output voltage at some predetermined voltage. Over a limited range of input voltages and load ranges they are reasonably effective, but the user must be able to tolerate the resulting high series dynamic impedance, limited regulation range, inrush current limiting and high parasitic power loss (poor efficiency). On the positive side the do inexpensive regulation at the lower Kva ratings and~vife significantly under rated with respect to load current (less than 50~), they provide a significant amount of single cycle fill-in. They offer no lightning protection and only low frequency RFI filtering (1 KHz to 1.5 MHz) in transverse mode only. (3) The motor driven or manuall o erated to switcher/transformer is a good alternative where slow reaction tame and switching transients can be tolerated. These devices use multi-ta transformers that are switched to regulate the output voltage. The motor driver options are expensive and no longer a cost- effective option. These devices offer no lightning protection and very little low frequency filtering. The usual configura- tion creates significant transients during the switching operation. -29- .i ~ T (4) The motor driven or manuall ad'ustable transformer (variable transformer, Variac) is very similar in concept to the tap switcher (3) above, except the taps are Closer together (one per turn). These are a significant improvement over the tap switcher, but display the same disadvantages to a lesser degree. For example, the switching transients are normally much lower. These units do have a wide range of control, but little filter- ing, and the added costs render them non-competitive except for special applications. (5) Electronicall switched transformers include two basic types, zero voltage crossover switching and zero current crossover switching. Of the two, zero voltage switching is the more popular because of the lower cost. Both concepts permit fast switching, as much as once every half-cycle if necessary. Both can be efficient, up to 96~, both can be produced with as much isolation as the so-called super-isolation transformers, and both can be produced with any number of options. On the nega- tive side, bath cost more for low Kva ratings and both suffer reliability problems because of the complex electronic control requirements. The zero voltage switcher senses the peak voltage. When it strays beyond the prescribed boundries it then switches to the next tap, up or down at the next zero crossover voltage point. Often, a significant transient is generated, and further, two switches can be in the "on" state at the same time and switch- ing jitter can occur when the line voltage tends to hover at a switching point. The zero current switcher usually senses the peak. However, they switch at the next zero current crossover point. To do this they must sense current flow as well as the voltage which adds to the complexity. The Perfect Power Source (Patent Applied For) The perfect power source must regulate, protect and filter. If only part of these functions are satisfied the unit is incomplete and only partially effective. The LEA Perfect Power Source (PPS) provides all of the required functions in one package as shown by Figure 16 including protection, broadband filtering and regulation. The system it services is pro- tected against any anomaly short of complete loss of power, much less than one percent of the possible hazards. The PPS uses the inherent filtering capability of the Kleanline Electronic Filter as the basis for the PPS design and simple, reli- able relay switching to change the taps. The two problems formerly associated with relay switching are overcome as follows: (1) The slow switching problem and potential loss of a portion of the sine wave was overcome by using a close-before-open concept. -30- .~ r • (2) The potential switching transient and short circuit current resulting from two taps closed for an instant millisecond) has been eliminated by the filter (components as illustrated by Figure 17. The resulting LEA PPS regulates the output voltage to within 5$ of the nominal voltage with input variations of from about minus 25$ to plus about 10$. Rapid tap changing is eliminated by switching only when there is at least a 1~ change in output voltage. No significant transients, noise or RFI are generated within the PPS or passed through it. No portion of a sine wave is lost or distorted. No harmonic distortion is introduced and the dynamic impedance is not significant. Table 6 presents a comparison of pertinent performance character- istics for the ferroresonant regulators and the LEA Perfect Power Source. The only requirements the PPS does not satisfy are those related to loss of power on one or all phases. To overcome the single phasing, warning and automatic shutdown options are offered. Compare the PPS to ferroresonant devices that claim to provide single phase or loss of cycle fill-in, but offer only some small measure of capability by derating the re ulator by as much as 50$. T~~ 6, COA4PARISON OF REGULATOR PERFORMANCE CONSIDERATIONS FERRORESONANT PPS (1) Load Sensitivity Regulation Range Dynamic Impedance Noise Filtering Waveform Distortion Inrush Current Impact Carry-Through Capability Cost Factor Harmonic Distortion Efficiency Lightning Protection Audible Noise Over-voltage Protection Very Sensitive +10$ -20$ maximum(4) Very High About 1 Khz to 1.5 Mhz High (4) Field may collapse, will create transients If oversized about 100$(3) .See Figure 17 High 50 to 85$(2) NONE High NONE Notes: (1) The LEA Perfect Power Source (2) Directly related to percent load vs rating (3) Inversely related to percent load (4) Load Sensitive Insensitive +10$ -25~ Low 1 Kc to 200 Mhz NONE NONE Less than ~t cycle See Figure 17 NONE 90 to 96~ Unlimited Insignificant Protected -31- ~" FIGURE 16 The Perfect Power Source Lightning Common & Protection Transverse Filtering Input: 80 to 135V RMS voltage Control Output: 115V t 5V RMS FIGURE 17, REGULATION CONCEPT, PERFECT POWER SOURCE i~ -32- l s a s ' SUMMARY OF PROTECTION RECOMMENDATIONS We have found that there are three levels of _ ments, and this mandates three levels of protectorsttonsatisfye / these requirements: (1) For protection against destructive anomalies use the Surge Eliminator (SE), (2) To add protection against disruptive transients use the Kleanline Electronic Filtering Systems (MB), . (3) To add voltage regulation use the Perfect Power Source (PPS). Relating this to the incident risk established by Table 4, Table 7 below identifies the scope of protection provided. TABLE 7 Selecting The Protector Anomaly SE MB PPS Overvoltage ALL ALL ALL Undervoltage None None ALL Transients Destructive ALL ALL Outages None None None Percentage Eliminated 29°~ 78% 99%+ Comparing the Perfect Power Source to competitive protector/ regulators, Table 8 below establishes the advantage of the PPS over the rest of the marketplace. TABLE 8 Regulator Performance Comparison Type Ferroregulator Isolation Transformer Competitive Switchers PPS Percentage Protection Against: Destructive Disruptive None 10°~ None 27% None 12y0 ALL 99°~ *One form of disruptive anomaly can only be eliminated by some form of constant voltage source, such as a generator plus a UPS. One or the other will only eliminate some portion of the remaining one percent. .. _~~ f .~ s BIBLIOGRAPHY (1) Lightning Strike Elimination, The Story of Dissipation Array Systems, Roy B. Carpenter, Jr., September 1979, Report No. LEA-79-1 (2) Protection Requirements and Concepts for Data and Control Lines, Roy B. Carpenter, Jr., November 1980, Report No, LEA-80-8 (3) World Distribution of Thunderstorm Days, World Meteorolo ical Organization, Secretariat, Geneva, Switzerland, 1953 g (4) Atmospheric Electricity, A. Chalmers, Pergamon press, 1967 (5) Lightning Protection, R. H. Golde, E. Arnold Publishers, 1973 (6) Lightning, M. A, Uman, McGraw-Hill, 1969 (7) The Lightning Book, P. E. Viemeister, The MIT Press, 1972 (8) Lightning Protection, J. L. Marshall, Wiley & Sons, 1973 (9) Characterization of the Electrical Environment, D. W. Bodle, et al, University of Toronto Press, 1976 (10) IEEE Guide for Surge Voltages in Low-Voltage AC Power Circuits IEEE Std. 587-1980, Sponsored by Surge Protective Devices Committee of the IEEE Power Engineering Society -34- .. ~. .. ... Part I-on the power lines Dealing with lightning... he progress in electronic systems Tdeaign has brought with it an increased sensitivity to the operat- ing environment and to the interface rnnnections. These interfaces bring with them both the desirable and the unde- sirable. The interface of concern in this article ie power lines. The power lines bring in the motivat- ing power for the cable system. They also bring destructive and disruptive electrical transients, herein termed anomalous events. Destructive anomalies are electrical events superimposed on the normal line wltage that cause it to be elevated above the safe level or operating range of the equipment it feeds, regardless of the character. This is normally taken at 120 percent of the normal peak wltage. Aa an example, it would be between 200 and 250 volts for a 120-w1t RMS line. Disruptive anomalies are electrical events superimposed on the normal line wltage that create a situation within the unit fed that causes it to momentari ly malfunction. This momen- tarymalfunction cauBes erroneous oom- mande, creates faulty data or "locks up" a system. This can bean annoyance and sometimes costly in loot time. but does not cause damage. This article is an attempt to elimi- nate some confusion on lightning pro- tection by deCning known hazards and comparing the performance of con- temporary protectors with the hazards. thus providing a reliable decision tool. The data used to define the hazards has been taken from 'a wide variety of publications on the subject. One of the problems related to light- ning protection ie the jargon used and the way it is used.'ib eliminate misun- derstanding, it is necessary to define beaic terms encountered in discussing lightning. An over voltage occurs when line voltage ie elevated to well above the normal RMS voltage and sustained above that level for a period in ezoA~e of one cycle (over plus 15 percent). An under voltage occurs when the 1tMS line wltage drops to what ie termed the "brownout" level and re- By Roy B. Carpenter, Lightning Eliminators & Conaullanti mains at that level for a period in excess of one cycle (over minus 20 percent). An energy surge is a rapid increase in the flow of total energy (joules or Watt-seconds) to the service entrance that is sustained for periods of less than one-half cycle. Single phasing occurs when one phase is dropped prior to the service entrance. ~~ 3~ Transients are usually considered as random voltage pulses of relatively high magnitude, but short duration, usually less than about 100 microse- conds. Electromagnetic pulse (EMP) is a single pulse o[ energy created by a collapsing magnetic field such ae that created by lightning or a nuclear burst. The magnitude can vary from insignif- icant to devastating. Switching transients are created by the public utility during load ewitch• ing or power source switching actions. They are also the result of other nearby customers, usually on the same feeder, switching on and oQ' high-current de- vices. A joule is a measure of energy, the product of volts, amperes and time. It FIQur~ i Number of Lightning Days per Year I Ths probaNNNy of MpMNsp for each day h: Iso number t X65 I rha m.~e A« th. usn k o.2~ «. probabiBly a rgnts~ on one a.y ouA a ~. • Flpurs 2 • Sample Surge Voltage as a Function of Distance from Stroke to Line 2.400 2.000 r+ Mile ~'n ~~^ ~c A !Ails A.600 2 idles s . A,200 • .~ ~. 0 1 2 J 4 _ 5- e Tbas M pass !~ Communieatiom BnRineerinR and Ikaisn June 1987 LIGIITNI NQ The shape of t~pical lightning , : stroke current f ow rises rapid y to its peak and then tapers off relatively slowly. is the only true measure of protector performance. A Watt is the product of volts and amperes only Destructive wltage anomalies that permanently damage connected compo- nents may be categorized as•naturally caused or man-made. '1>able 1 lisle potentially destructive anomalies by cause. Natural hamMs Moat naturally eaused line voltage anomalies are related to atmospheric activity of one sort a another. Lightning- related anomalies can be the result of either cloud-to-cloud or cloud-to~arth events. These, in turn, are related to such factors as the geographical loca- tion of the site, the ieokeraunic somber related to that location and the time of year. Figure 1 is an ieokeraunic map of the United States. The number defines the potential number of lightning days that can be expected in a year at a given location. The number can be used to estimate the probability of lightning for a given day (if seasons are disre- garded) and the number of strikes that may be expected to terminate in any given area for that year. In applying these data, two factors moat be consid- ered: It ie an estimator only and can vary considerably from year to year, and it takes only one strike to cause irreparable damage. Lightning in general can cause three specific Corms of hazards: Direct strikes producing power surges, induced tran- sients from nearby strikes and the EMP from the strike's magnetic field. Power surges result from a direct strike to any or all phase conductors near or at some distance from the facility. The character of these surges is, therefore, directly related to the character of the lightning stroke, the line it strikes and the distance to the point of concern.'Ib define their specific character, an engineer must look at specific cases or parameterize the rise time, stroke-peak current, distance bet• weep atrokea and facility or the result- ing line impedence, and the' grounding resistances at significant points in between. One signifiant factor ie ehawn by Figure 2 where the Burge voltage ie estimated for an average lightning strike Cor various distance from the station of concern. These numbers must be greatly increased Cor higher energy strokes. Other measurements indicate that these voltages could achieve levels in excess of 100 Kv if the wire inaulntion would support that potential without arcing and if the measurement point were near the ~ stroke. The higher voltages seem to be 'the norm, rather than the aooeption, r for FM and TV transmitter sites. The shape of typical lightning stroke current fioN- is such that it rises rapidly to its peak and then tapers oiC rela- tively slowly, following slog-normal shaped curve. There are two classes of lightning atrokea: The impulsive stroke and the non-impulsive or hot stroke. This characteristic determines the damage caused. The impulsive stroke causes most of the damage to electronic systems. Since they embody a large percentage of high frequency energy, the rate of rise exceeds 10,000 amperes per micro- second and can achieve rates of over 100,000 amperes per microsecond. They last for no more than 100 microseconds. The non-impulsive or hot stroke rises much slower than the impulsive ~. stroke, as low as b00 amperes per microsecond. However, it usually Isats much longer, extending out to ea long as 10 milliseconds to the b0 percentile. These atrokea are responsible for many fires and explosions. Induced transients are the second order effects of lightning activity in or near the area of concern. Their charac- ter is related to the lightning discharge and the system character into which the transient is induced. In general, they are high voltage, low energy disturbances. Estimates of the poten- tial for this disturbance phenomenon range up to 100 Kv. This value is more dependent upon the system circuit parameters than lightning itself; inatalla- LI~:IIININi: f Earth-current induced transients are created by Ilghtning strikes to earth, to or near the facility of concern. tin breakdown levels usually limit the peak voltages to much lower levels, except on primary feeders. Public util- itica have found that tl-is phenomenon accounts for most of the lightning faults on lines with a potential of 20 Kv and lower. Lines as short as 60 feet can pick up a significant transient, depending on their proximity to the stroke. These induced transients tend to take a shape related to the ditTer- ential of the stroke itself-short nega- tive and positive pulses of less than 10 joules. Induced transients are created by one of three related phenomena. They are the result of tl-e invisible but highly potent electrostatic field found between the charged clouds and the earth. This field moves and varies in strength with the charged cloud activ- ity. Atmospl-erically induced.transienta are created by sudden variations in the electrostatic potential of the atmo- Fphere. Where the clear air field n-ny be 150 volts per meter elevation above earth, during an electrical storm this field can achieve levels of up to 30,000 volts per meter of elevation. Neartry cloud-to-cloud and cloud-to-earth dis- charges can cause significant Held variations continuously throughout the storm period, on a random basis, in both time and magnitude domains. A Held can be shown where both the suspended power lines and the inter- plant data lines experience induced transients when a charged cloud in the area oC concern charges everything on the aurfaoe of the earth beneath it, to an equal but opposite potential by induction. The field between tl-e cloud and earth can achieve 30,000 molts per meter. A wire elevated above the earth by 10 meters in this field would be charged to. a potential -equal to its surroundings, whichcould theoretically equal ea much as 300,000 volts witl- respect to earth. A sudden lightning THE O10 WAY Ar~ASr.- TNf RIGHT WAY 'E1DM-~ THE ONLY TV AUD/O DEV/AT/ON METER MADE fOR CABLE THE D/GlTAL ANSWER TO AN OLD ANALOG PROBLEM • Digital Storage Meter • Predsion Deviatkx~ Calibrator • Measures Tones or Program Audq • Measures Peak Deviation • • Measures RMS loudness • Measures TV Modulator Unearity • Measures TV Modulator Frequency Response • Compares FM Daviatbn on AU_ C~nnels /NTRODUCTORY PRICE S695. UNT/L AUGUST 1, 1987 CALL YOUR ORDER /N NOWT FM SYSTEMS, INC. (7141979-3355 3877 S. Main St. 600-235-6960 Santa Ana, CA 92707 >f0 Communicatimui EnRinecrinx •nd Lheign June 1987 Reader Service Number 17 discharge to earth or another cloud will cause tl-is field to collapse, leaving the elevated wire with a bound charge, ~vl-icF- seeks ground through any avail- able path, even jumping large insula- tors in the way. This creates a voltage pulse that can exceed 100.000 volts at times. 'IYansients resulting from elec- trostatic field changes can be prop~- Baled over long distances, depending on tl-e circuit parameters. As an example, a nearby cloud-to- cloud discharge or a strike one mile away wilt induce as much as ?0 volts per meter of exposed wire into a thus connected system. Earth-current induced transients are created by lightning strikes to earth, to or near the facility oCconcern. With tl-e termination of a stroke to earth all tl-e charge induced into the earth by that cloud must move from the point where it was induced to the point of impact of the stroke, and thereby nPUtralize the charge. As a result of this motion of the induced charge, earth currents are set up within the earth's cruet on or near the surface. Any good conductors buried in the earth within the charged area will provide a preferred path for these earth currents and thus be the recipient of these eevere earth currents. The results are transients within the conductor, either directly or indirectly related to tl-e earth current character. Current along the sheath of wires will induce transients into the inner conductors through mutual induction, or these currents will be superimposed on the conductors without sheaths. Electromagnetic-field induced tran- sients are also created by lightning discharges. Fbr this phenomenon the IiRI-tning (lash channel acts as a ver• tical radiator or antenna. The large flow of current in a short time down the ionized lightning flash channel sets up a rapidly changing electromagnetic field propagating out Crom the stroke channel in much the same fashion as a broadcasting station using a single tower/antenna. These waves propagate Cor many miles and are the cause of static in a radio receiver, reelected waves in the transmitEers and tran- sients in nearby conductors. Generally, cloud-to-cloud strokes produce predo- minately horizontally polarized waves, ~. .. 1.1~:11'I NINA: Profecllon requirement 9'he protection requirement, if lim- ited to destructive anomalies, must be derived from a composite of all the potentially destructive causes. A summary of the resulting design requirements by key design parame- ters follows: Peak voltages 45,000 wits peak-surge current 200,000 amperes rise-time response 50 nanosernnds peak-surge energy 100,000 joules loss of phase 10 cycles or less mrrwltage line +20 percent underwltage line -30 percent It should be understood that it is possible to enrnunter situations well beyond these parameters. Aa an exam- ple, studies have shown that FM radio and television stations, because of their location in. remote or elevated areas, nre subjected to the higher energy level, fast rise-time surges. The designer must select the rfsk considered acceptable and design the protective system to satisfy those parameters. The designer must, therefore, Aelcct the risk considered acceptable to hi9 client and design the protective system to satisfy or exceed those parameters. The foregoing list defines the safe basis for design. All systems must exceed that capability by a safe margin and then Cail-safe for 100 percent pro- tection. Protection corrCepts Lineprvtecrtors faU into three classi fica- tions: Filtero. surge or transient protec- tors and voltage regulators or isolation transformers. The conventional line filters are primarily limited to the removal of radio frequency interference (RFI). Power surges and other distur- bances are attenuated very little. Line transformers are available in one or a combination of tow types: Regulators or isolation transformers. Regulatore usually maintain a given output volt- age over a range of input voltage variations of up to ±30 percent. The isolation or super isolation transformer is a low-pass filter with up to 120 dB of attenuation across a limited RFI band. 'T'hey do not protect against lightning- related power surges of significant magnitude or all modes of noise. Devices Bold as °eurge protectors" often have similar, and thus, confusing claims. They are seldom related to a well-defined hazard. Any candidate moat be evaluated against the total spectrum of performance requirements as previously defined. Firnt, how~wer, the applications con- cept should be considered. There are tvuo ways of implementing surge pro- tection into the system to be protected. The protector may be installed in parallel with the device to be protected or it may be installed in series, prior to the unit to be protected. Most conventional protectors, except the LC filters, are designed to be wired in parallel with the load they protect. R.i.G.' YERSALIFTS-Ready for You -Right Now! When you need a lift in a hurry, call your Versal(it Distributor. He has fast access to our R.T.G.' pool of complete, mounted Versallits. No waiting because of Ivng delivery on vehicles. manufacturing delays, or freight problems. Best of all. they're Versallits, with job-proven reliability and industry-wide acceptance. And, since we're mounting them in quantity, the illllll prices are right, too. Truck or van mounted, telescopic or "elbow" models, with working heights up to 55 feet. all ready to go to work - Nowl ,, `Ready To Go Mounted on current model chassis. t _' !2 Communicaliom Engineering and Design June 1987 For the name of your Versalltt Oistritwtor, calf: o~ ~rrm~ ,,~., Kn,.~ ~.~. P.O. aoa t0]N w.~e, Tz »~ot-0xt pal ns~o+oo -^-~ '','~~ -Reader Service Number 10 •., ; i~ / ~ 1• .~ LIC NTN I NC The series hybrid protector r . concept is the only concept that can be made 100 percent effective. The parallel protector's efT'ectiveneea is compromised by two factors: 1. Because it forma a parallel circuit with the load to be protected, the load moat share the disturbance it is to be protected against. As a result, the protector reaction time is very signif- icant, as is the clamping ratio (ratio of peak line wltage to voltage at the peak-surge current). In actual cases, measurements have proven to be very high, in excess of 10 times the normal line voltage at the peak of the surge. 2. The wiring that connects the paral- lel protector into the circuit becomes a aeries impedance to the rapidly clamp- ing, high surge current, thereby adding the voltage developed across these series impedencee to the high clamp voltage. By way of contrast, a aeries hybrid protector is in series with the power feeding the protected unit, thereby acting as an interceptor to any incom- ing disturbances. The negative etTects of connecting leads, reaction time and even clamping ratio are overcome through use of series elements and by separsting the paths for the surge current from the clamping control ele- ments. An examination of the forego- ing factors alone is sufficient to demon- strate that the series hybrid protector rnncept is the only concept that can be made 100 percent efi'ective. fut~ Nlminafors The LEA lJynatech surge eliminator (SE)O designs are all based on the same concept, with the acme objectives. In addition to the previously defined requirements, the SEa must react wi th i n 6 nanoeeoonda; eliminate at least 99 percent of the possible disturbances for the particular application without loss of the protector or protected function; fail-safe above the 99 percentile by opening the circuit of the protected function; and eliminate even the high frequency, high voltage impulse spike. 'Ib illustrate surge eliminator per- formance, consider the situation de- picted in Figure 3. Part A presents a badly distorted sine wave fora 120-volt RM3 hot-to-neutral situation where several forma of voltage anomalies are illustrated. The equipment destruct level is assumed to be above about 250 volts peak (to pmtect reliability). The surge protector must, therefore, pre- vent the voltage from rising signif- icantly above that level. 'Ib accomplish this, the SE functions are ae follows. First, the voltage con- troller assembly constantly monitors the output voltage. When it rises above the clamp voltage, which is usually set . at 1.2 times the normal peak voltage, it acts ae a constant voltage device hold- ing the voltage at the selected clamp level. If the anomaly is more than a small transient it turns on the high energy dissipation assembly. Some of the energy is dissipated within the unit TV STEREO FEATURES INCLUDE: • Dual Stereo Inputs...for Local Ad Insertion or Back-up Audio • Stereo Synthesizer 8uilt~n . • Separate Video and 4.5 MHz Loop- throughs • Level Controls accessible from front panel • Deviation Test Tone Built-in • Self-contained, rack-mount unit. only 1.75 inches high • Optional Audio Processing (Automatic Gain Controp ., 1a0 McC~nlek Awnw Grra Moan, CA s!s=s t.fiAMINc7 IfVOIJsdTTilEB I714f •7t-4611 nlvx: s1o soo 4as: .a Reader Service Number 20 l'~mmunicaliona f:ngineerinR and IhsiRn June 1987 I3 Learning Industries MTS-2 BTSC Stereo Generator, with dbxc9 companding, provides cable systems with a means to transmit BTSC stereo TV audio. All SEs are designed with a special surge fuse that will open If the capability of the SE Is exceeded to compensate for the influence oC the grounding system surge impedance. 7'lre remainder ie dissipated in the grounding system and its connections. During the SE operation, the voltage to the protected system is maintained within the operating limits of the system, neither being crowbarred to or near ground potential, nor allowed to rise significantly above the.clamp level. Aa soon as the surge or transient has Passed, the SE returns to its passive mode. The SE series elements contain a low-pass filter to accomplish the energy conservation control functions and min- imize noise and impulse transients Negative going spikes on the positi half-cycles and positive Roing spike on the negative half-cycles are site nuated to some degree, about 10 dB. LEA surge eliminators are designs to provide rnmplete protection. SF. wilt handle at least 99 percent of th potential surges or transients the vwuld experience in a particular appl ica- tion. Beyond that, all SEe are designed with a special surge fuse that will open if the capability of the SE is exceeded. Note that the fuse-blow characteristic ie a decaying exponential that asymp- totically approaches the circuit operat- FIGURE 3 ~ • Surge Eliminator Protect(ve Action 8elore ProteMlon • ~ ••Destruclive Surges ---~r-_t_1-----~----~----------- tss---1~.-J-_...r------I~---~----~-~ - -- ,~ -tti6---- - - -- ----- ----rr--------- -cw-~.-----r-----. L-- --...-----~ B. Aller Proteclbn .200- .Clamp Level --~---~-1-----rst------------- I~t66-- Note tlphl Clamp - '~'-tt------ ~~----- -- ' -- . s ;~ / -200 --- -- - - - . -- -v ~ - ~ - - -Clamp level ing current. The SE will dissipate any ve energy below the curve and above the s operating current level and the fuse will protect against any unusual event that would introduce energy in excess d of the SE capability. The probability s for this event ie leas than one chance e in 10 years for the average location y within the continental United States. The rating of SEs in terms of power handling capabilities is not a simple matter. Although SEa can dissipate energies in excess of 100,000 joules per phase and handle surge current (lows in excess of 200,000 amperes, this does not completely describe the protection provided. The LEA SE design is such that it makes use of the grounding resistance and power system surge impedance to increase the overall pro- ~ tection capability significantly. The principle can be illustrated in which a worst case lightning strike of 200,000 amperes is assumed to have terminated at a hilltop utility pole. The pole is assumed to be within 35 meters of the users terminal wherein a LEA SE is used Cor surge protection. The parame- ters selected are typical fora moun- taintop facility, or perhaps a bit on the optimistic aide. Referring now to the related equipment schematic diagram, it may be seen that both the surge impedance of the connecting wiring and the grounding resistance are used to dissipate a major portion of the stroke released energy, moat of which is in the grounding resistance. That ie, the excess energy heats up the earth around the grounding components. Flom these data it is evident that the SE could provide protection against light- ping induced energy levels in excess of a total of 100,000 joules. The clamping ratio (CR) is also a factor oC importance in rnnaidering a surge protector. The CR is defined ae the ratio of line wltage under the worst case lightning surge current va. the initial clamping level. Fbr all surge protectors the terminal voltage permit- red at the protected equipment rises with a rise in surge current. Obviously, the Tower the CR value the safer the protected unit ie for any given set oC rnnditions. ' ~ This article will appear in three aeclions, ending with August. Part 2 next month: Now to cope with direct strikes. ~• ~~ Communicaliona EnRineerinR and DeeignJune 1987 I ~, July 15, 1988 Mr. Michael J. Kelly >?. 0. 13ox 655 Riclunond, Virginia 23219 Dear Mr.Kelly: ~~~9~~~ We are the owners of Office Condominiums located on Twinridge Lane, Chesterfield County, Va. We have indicated, in yellow, on the attached County of Chesterfield Tax Map 18-15, the location of our properties. An application made to the County of Chesterfield by Contel Cellular, Inc, requests permission to install a 198 foot Conrnrunications Tower in one of two locations as shown in red and blue on the enclosed Chesterfield County Tax Maps, 18-15 and 18-16. In either of the proposed locations you can readily see the nearness of such locations to .our ,off ice buildings. 7.'he area in which permission is requested to locate such a tower is composed, almost ;entirely, of residential, office and quiet retail use. Certainly to ask to intrude .into such a highly developed area with such a tower is inappropriate. Collectively we have an investment in the Twinridge Condominium Office Development of approximately $ 2,295,000.00 To consider placing such an installation as this tower as close to our development as has been requested, and in constant view, is extremely objectionable to us. '1'he applicant should be required to acquire a location where the location of such an installation would not act to adversely affect the value of properties that have been developed in the immediate area. In addition the presence of such a tower in either of the proposed locations will certainly tend to neutralize the aesthetic appeal of all of the properties in the area. We ask that you assist us in protecting our properties by voting to oppose the locating of this co;rimunications tower in either of the proposed locations. r- ~, !~... ame (s) ~ ~~ LS ( ~l Address ~(,~ Telephone Name(s) Address Telephone ~'.~,~- ,,~77 - ~os-~ Telephone Name (s /., ~-- w7 ~W I N ~ ac' I aw-~ Address Telepho e -_:_---/ ~~ y`~ Address ~' ~1 July 15, 1988 Mr. Michael J. Kelly P. 0: Box 655 Rictunond, Virginia 23219 Dear Mr.Kelly: We are the owners of Office Condominiums located on Twinridge Lane, Chesterfield County, Va. We have indicated, in yellow, on the attached County of Chesterfield Tax Map 18-15, the location of our properties. An applical-ion made to the County of Chesterfield by Contel Cellular, Inc. requests permission to install a 198 foot Conununications Tower in one of two locations as shown in red and blue on the enclosed Chesterfield County Tax Maps, 18-15 and 18-16. In either of the proposed locations you can readily see the nearness of such locations to our office buildings. The area in which permission is requested to locate such a tower is composed, almost entirely, of residential, office aiid quiet retail use. Certainly to ask to intrude into such a highly developed area with such a tower is inappropriate. Collectively we have an investment in the Twinridge Condominium Office Development of approximately $ 2,295,000.00 To consider placing such an installation as this tower as close to our development as has been requested, and in constant view, is extremely objectionable to us. The applicant should be required to acquire a location where the location of such an installation would not act to adversely affect the value of properties that have been developed in the immediate area. In addition the presence of such a tower in either of the proposed locations will certainly tend to neutralize the aesthetic appeal of all of the properties in the area. We ask that you assist us in protecting our properties by voting to oppose the locating of this conununications tower in either of the proposed locations. Very truly yours, ~ ~~ti Name (s) ~ ~2 Name s) ,jG~" ~~1`L~sivllfa6a LA. ~incr-~ yr L323r Address r;: ~, ~: 2.7 z.-7S 9 3 Telephone ~. .n ~fi ~' Name(s) Address Telephone ~o ,~ ~~/~.~, ~~u, ~3y3 r Address Telephone .r Name ~% A~ ~~Y~~ Address ~~~- 7~7J Telephone llate hlr. Michael J. Kelly P. 0. Box 655 Richmond, Virginia 23219 Dear Mr. Kelly; We are writing you, as the riidlothian Representative of the Chesterfield County Planning Commission, to express our grave concern regarding tite application by Contel Cellular, Inc. for permission to erect a 198 foot coirnnunications tower in one of two proposed locations, referred to in the application and as indicated on the County of Chesterfield Tax Map 18-15. We, the undersigned, the parents, and in some cases the grandparents, of the children attending The Good Shepherd Christian U:ry Care Preschool facility at 100 Buford Road. One of the proposed locations for the Tower is in[mediately at the rear of the play area for our children. '11te other location is very close by. As you know there is st-i11 a difference of opinion among the experts in the scientific field regarding the effects of Microwaves on the h wnan body, In addition to this possible detrimental effect on our children we are concerned for tltelr safety it t-he proposed 198 foot tower is installed and shou:Ld fall. While :i.t will be a great inconvenience for us to transfer our children to anoL-her facility, because of the distance involved from our homes, and certainly disastrous economically to the operators of this well operated facility, we will remove our children from this facility if approval is given for Che er.ectio^ of this Cvt[mtunications Tower in either of the proposed locations referred to in the applications of Contel Cellular. We earnestly and respectfully ask that you not approve either of these requests. Very truly yours, / ~ Name ) Name(s) ~~~- l I~e--l~-o-c9. ~ Street Address Street Address ~~- ~~7d Te lepltone ~~G-oy6/ Telephone C -' __L_~ Na e(s) Name(s) Street Address Stre t Address ' Page 2 i Letter to Mr. Michael J. Ke11y from the parents of children attending The Good Shepherd Christian Day Care Preschool facility at lU0 Buford Road (continued) Name (s) 9~'iy ~~d. ~ . Stree/~ress J ~•~.. a 3 ~~s ~a ~ -a ~~ - ~~ s-g Telephone Name(s) ~)~~ 1_rY1~JPC~, v,~-I3~3~a1~ ~ ~ ~ ~~~~a~~ '~~ ~'er`~~~°~s'1 Street Address Telephone ~ ~/1'~-/ ~~ Name(s) ~~- Street Address g~~-3~ -s~c~~ Telephone Name (s) Street Address _~7~- ~o L ~. ___ Telephone %~ ~~ ham. ~cQ Ca~!~ _ Name(s) Street Address -____~` 1 a e(s) ~aO ®~o ~~r~-r ~ wc, ~ . Street Address ~g~-o9~L 'Telephone ~~ ~ 'Lt ` /C / /' -~r~ Azyl ., ame _s ~~ Cd ~ ~~~li~ ~c~ ~ ~ _ Street Address Telephone ~ ~~~ ~ ~~ Name(s) ~1~~~ ~- Street Address a-~ v~~~ ~ Telephone ~ ~~~ ~ Name ( ) ~s73 ~ CMG: ,_ l~~ Street Address 'Telephone /Uoic~. J. /y1as~ Na-ne (s) Street Address Page 3 `,~ ) Letter to Mr, Michael J,-Kelly from the parents of children attending The Good Shepherd Christian Day Care Preschool facility at 100 Buford Road (continued) Name (s) Street Address ~--~L - 3 t, ~~ Telephone ~~2he~ d ~~ "`~ Name(s) ~~~ S ~~ ~ Street Addres ~~u-1U~~ Telephone Name(s) 079// ~'- ~6~/ ~~- ,C'-,~- I~ Street Address '1'e 1 e phone / ~ ' ~~ W e s) / ~~yl~c.~.. ~,~ . Street Address // 'Telephone J ~o yCe ~ ~ ~~Ll.~g-~~-Y Name(s) Street Address x'72-2~c~ ~ Telephone ~~U Z.~/ Name(s) Street Address 't'elephone 1/. ~~ Name (s) Street Address Telephone / ~/ ./ Name( ) l~ s a- tre t Addr c.~ yd ~ ~ ~ ~ 9'9X ~J; ~~ ~s ~R . Name(s) / Street Address /Telephone F- . 1`s Q ~ Name (s) ~v i ~~--~~ Q ~~~~ Street Address Pa€,e 4 Letter to Mr. Michael J. Ke11y from the parents of i chi. ].dren'attending The Good Shepherd Christian Day Care Preschool facility at- 100 Buford Road (continued) Z - -a-• IA- c... /. Fit IBS N-~4- L Name (s) L~ 3~--5 J~~k~ NS ~ _ Street Address _a-76 - `~6/~ Telephone Y ~_ ~~ U Name(s) ~ ~ w ~~ ~~~.,c~ ~ c~~r Street Address ~~ ~~ ~~ ~ Telephone Name(s) 1 c,.. _ . ~._.. Street Address ,. Telephone j C~- , N:~me (s) ame(s) .. ~ n~ Gc Strellet Address r J _. _ ~ P (~, ~_ // 1'e le phone ~_ Name(s) ~'~7oC~ ~a-~l~l~a~ti (},'tee ~_e_ Street Address ~7~~~- ~~' 1 y~ elephone ~~a~~~~~.o~ ~ ~~ ~~~~.~ Name(s) /'7 ~ ~ J (.~i~J7ZL,DZ 1 Street Address ~ y y z ~ m ~~wc~ ~~ ~,~ Street Address 2 72 - ~~s' Telephone I ~ ~~ _ ' ~ ~~~ Name(s) Street Address Telephone ./; r_ _ - r' N me (s) r ~ ~ ~~ Street Address ._._.~ ~) ~~ rte/ - L ~ `~ ~ G~ 1'e lephone ~ ~ ~~ ~ o _ Name (s) ~ ~c~o ~ ~~.as2. l-, n Street Address ' Page 5 ,,1 Letter to Mr. Michael J. Kelly Lrom the parents of children attending The Good Shepherd Christian Day Care Preschool facility at l0U Buford Road (continued) c. ', ~ ~ ~~ Name (s) '~ ( , ~ ` , ,, ' 1 ' r rr r l =~ ~ ~ Street Address ' ) l _~ ~ ~ r .~ Telephone ' ~ / U`" "`'`. Name(s) Z~~ ~~~~ Street Address '1'e le phone ~ ~ ( ~ / ~ t ~ ~ , i ~ i , :1 ,~ , ~,_ ~.: 1 Name(s) Street Address i'e 1 ephone Name(s) Street Address Sao ~ ~I ~ ~- Telephone Name(s) Street Address Name(s) Street Address '1'e lephone Name(s) Street Address Telephone Name(s) Street Address 'Telephone Name(s) Street Address 7'e lephone Name (s) Street Address ° Page 6 ~a Letter to Mr. Michael J. Kelly from the parents of children1attending The Good Shepherd Christian Uay Care Preschool facility at 100 Buford Road (continued) ~e(s) Name(s) 3 ~ 1 ~~ ~ i ~ i / /~ ~ ~ l . ~ , oc ~ / r Street Address . Street Address Telephone 'Telephone Name(s) Name(s) Street Address Street Address Te]-ephone Telephone Name(s) Name(s) Street Address Street Address Telephone 'Telephone, Name(s) Name(s) Street Address Street Address Telephone Telephone Natne (s) Name (s ) Street Address Street Address fnnml Crllular of Viryinia, Inc. 1104 West Laburnum Avenue Suite; iU4 Aiclnnund, VA 23271 804 3!ib k1!iUU == =-=~ CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality Address 7 ~DL. '~ ~~ Garr rr~°°...,,.~ r-ir . /7" V !4 ; j ~ 3 ~ ~~ f ~ ti' ;. i~ s~ l C~.~'~~-. yc~ z 3 ~-_~ ~, Z,3 2 3~ 2~! / 5 3~ Cuntcl Crllular of Virginia, Inc. 2104 West Laburnum Avenue Suite lU4 Hichmand, VA 23227 1104 3!i5 U5UII == CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area.. Name t . ;'~. ~}'~ (~,~-~,~.~ ~) ~(~, ' ~~~ rte; Address r~; e - ~~ ^~ 1, ;; r,r,~ ~ ~ ~ ~ .r: 5-Io'a l~ ~`l/ /4~<r <<'~-r~P ~ 32,E ~~a~ y'_ ~~~~~~~ ~~x. ~ ~3 ~~~ ~ ~ -- ~ ~ , - ~ - -- -- Z~f ._- -~ Coinel Crllnloi of Viryiniu, Inr;. 71(14 V~Ie;i Lal~wnum AVL'rIUC Suilr, lll4 Hiclunund, V/1 73221 O(14 356 U;~IIII --==-== CELLULAR To the Chesterfield County Board of Supervisors: Tfle undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that ire support Contel Cellular's request to construct a telecornnlunications tower on either Nortfr Providence Road or Buford Road, as the presence of a tower on either site ~,~ill substantially improve the quality of cellular service in the area. Name ~ r~ ,~, Address Cumcl CclUdar of Viryinia, Inc. 2104 West Lahurnurn Avenue Suite lU4 Richmond, VA 23727 004 355 0500 == CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. Name o ~~~~ ~~ ~ //;; r ~, y„ / UfoG ~ P :~T J~~,~ ~d d a~3 / ~2i sfw~ o ~D~e4'~ ~,~ ~~r e~~r,/a3j3/ r ~ -C ) ~/' -~~ _ Address )~ - - ~~ !~~ . ~~' i __ Guucl Cnllulor n( Vir~inin, Inc. 2104 West Laburnum Avenue Suite 104 Richmond, VA 23227 1104 3!i5 0!i00 == CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road,. as the presence of a tower on.,either site will substantially improve the quality of cellular service in the area. Address 2 9 sa c%o a aRi;d ~E fin. IDf,e M,v~~~y.., . ~'~_~ e~N e c ~9ryPd ,E''c.h nta~ fin. a~ 3n l~~« s-f ea dl ~ ~ . r~ ~ d I o . 1/a ~ ~ 2. s !,3 ~ Z o o <. z 30(~ U '0 ' ~ Gf~.~~~ Z3~~ Y! ~ J r/,zfj~ ~~ l(.1 a31~ ~v~ Name Cuuuil I;elhd.u of Virginia, Inr. 2101 Wesr l~hurnum Avrnuc $uilr' iDd Ilichnn~rrrl, V11 23221 }liVi :155 ~~,np ~,«___- ~`---~~~ CELLULAR To the Chesterfield County Board of Supervisors: Tfie undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Celiular's request to construct a telecommunications tower on either North Pravidence Raad or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. ~.. ,111E-:: i -.3~: blED '? :4~3 Address 11l/~~ ~~`.~. ~ 313 SRr,, ~ ~ l o~ ~L..~~.tes~~D~ ~ ~ roLcc~r ~ :~3,3 .~~.~~.- 1 ~) I +-~- I L~ ~c~ /~a~a ~1. t~-(a~~ 10 . /~ ~ 23/lz ~'1..~i~/~~u~~31! z +'+ TC~THL PH~:~E . `r'te '+ + pp _ ~i v Canlcl Cclhdar of Viryinio, Inc. 2104 West Laburnum Avenue Suite lU4 Richmond, VA 23227 UU4 3!iU E{`,dl(I == CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. Address ~ 7 L.M GJDU ~f C /J ; ~ 9 ~S l ~2 ~~~ 1,,/ ~o ~ ~~ Cunicl Crllnlar ul Virpinin, Inr.. 2104 West Laburnum Avenue Suilu 104 Richmond, VA 23227 004 355 flhll0 -_= CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. Name f ~,ff ~.. l~ _. f= ~ ~ / w~. Address ~// / 7 :'~r"~C ; ,~„ l% ~--~ ,r N C' - I ~ ~ ~~.~s t-E'er' Conlel Cclhdnr of Virginia, Inc. 2104 West Laburnum Avenue Suiia lU4 Richmond, VA 23221 U114 3!i5 UbUU == CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. Name Address ~ ~ Z- ~ 2,u c.~~o ~', .., E~i-L, N. ~ ~.3Z3S ~~~3 - iOAaJ ~ vti.- ~ ,PL~~i ~CJ~.J 7 ~ l_ I~7 1lA~L a - ~~~ L C',1 ~, To ~-he, C~h ~s~(-e~'-~i ~lc~ ~,Q~_~oox-d y-F ~t ,~r~ ~- y i s o r s Tl~e. v~rd~ars ~ a ~~~ r e 5 i d.e_n--Fs o-~ C.hes-Fe...r-~' -el d '',S~ ~,,.tr,-F,~ we°S~, -{D i ~c~c'r n~P ~-~,a~t c,V~. sc~..poo~ w~t-~~ C ~ - c ~ - ~„ r `s r~e~ e s -f r~ c~r,.st r c.~ ~-~ a -~ ~~ ~ ~~ n-. ~,, c a /1 ~ r cx ~1 Ln s `~'bll~x' j~'1 ~c'"~'V~ L1r ~ O~"`l-~n ~ro ~ i d rn ~ R ~ ~~ 3 u ~~d P d ^Tl~e- .~ r~.~ 2.t~ C~ c)f a r~~ ~u5 -~r~ u~r t~1 ~ S l,~c-Frx r~,'a l C~ c i +~ ~rU~12 '~ ' ~-- r~ ~ ~ r - _ ~ , p,. ~Z3 {a 3 ~ ~ddd 4 ~~~ ~~~~~~ ,, z ~ ~ B a ~~~ ~ c~ s-e ~C Contcl Cellular of Virginia, Inc. 2104 West Laburnum Avenue Suite 104 Richmond, VA 23227 E304 3!i5 A500 -~ CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. Nam Address n , Contel CEllular of Virginia, Inc. 210h West Laburnum Avenue SUIfE ~()~ Richmond, VA 23777 BOh 3!i5 8500 =~ CELLULAR To the Chesterfield County Board of Supervisors: The undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contel Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. 3 Cliulol I;CISi',li 01 `ihi,~iniil, IN;. 2101 West lahurnum Avonue $~litc 1D4 Hhhn!w~d, VA 23221 f11N ;155 f3'.~OIM '~--~-~~. CELLIJLA ~~ a= = _ - R Ta ttre Chesterfield County Board of Supervisors: Tf+e undersigned residents of Chesterfield County wish to indicate to the Board of Supervisors that we support Contei Cellular's request to construct a telecommunications tower on either North Providence Road or Buford Road, as the presence of a tower on either site will substantially improve the quality of cellular service in the area. TI_~l_-.:?_,,.:, tdEIl .=±:44 Ltr_t:} .3~5 91?':~ F'.c~2 Address '~ /~ _/