ATIS 0600012 03-2012 Electrical Protection Considerations for Outdoor Coaxial Cable Runs for DS-3 and GPS Timing Signals.pdf

1、 ATIS-0600012.03 ATIS Standard on - ELECTRICAL PROTECTION CONSIDERATIONS FOR OUTDOOR COAXIAL CABLE RUNS FOR DS-3 AND GPS TIMING SIGNALS ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven standards for the informat

2、ion, entertainment and communications industry. More than 200 companies actively formulate standards in ATIS Committees and Forums, covering issues including: IPTV, Cloud Services, Energy Efficiency, IP-Based and Wireless Technologies, Quality of Service, Billing and Operational Support, Emergency S

3、ervices, Architectural Platforms and Emerging Networks. In addition, numerous Incubators, Focus and Exploratory Groups address evolving industry priorities including Smart Grid, Machine-to-Machine, Connected Vehicle, IP Downloadable Security, Policy Management and Network Optimization. ATIS is the N

4、orth American Organizational Partner for the 3rd Generation Partnership Project (3GPP), a member and major U.S. contributor to the International Telecommunication Union (ITU) Radio and Telecommunications Sectors, and a member of the Inter-American Telecommunication Commission (CITEL). ATIS is accred

5、ited by the American National Standards Institute (ANSI). For more information, please visit .Notice of Disclaimer however, it was written when the primary focus was on protection of hybrid fiber-coax plant for deployment of TV services to residential customers over RG-6, RG-59, RG-8, etc. - relativ

6、ely long run (thus more subject to EMI influence) coaxial cable plant with network-powered repeaters. While most of the test procedures of GR-2908 are applicable, this document intends to provide additional application guidance for outdoor DS-3 and GPS signals over 734A, 735A, low loss communication

7、s coax (such as LMR-400 or other LMR cables), hard-line coax, RG-59, and RG-8 type coax cable with relatively short (typically less than 450 feet) unrepeatered runs. ATIS-0600012.03 2 2 References The following standards contain provisions which, through referenced in this text, constitute provision

8、s of this ATIS Standard. At the time of publication, the editions indicated were valid (where no edition is indicated, the latest edition applies). All standards are subject to revision, and parties to agreements based on this ATIS Standard are encouraged to investigate the possibility of applying t

9、he most recent editions of the standards indicated below. 1 ATIS-0100510.1999(R2008), Network Performance Parameters for Dedicated Digital Services for Rates up to and Including DS3 Specifications.12 ATIS-0600333.2007, Grounding and Bonding of Telecommunications Equipment.13 ATIS-0600334.2008, Elect

10、rical Protection of Communications Towers and Associated Structures.14 ATIS-0600404.a.2005(R2010), Supplement to T1.404-2004, Network and Customer Installation Interfaces DS3 and Metallic Interface Specification.15 ATIS-0900101.2006, Synchronization Interface Standard.16 NFPA 70-2011, National Elect

11、rical Code (NEC).27 NFPA 780, Installation of Lightning Protection Systems.28 TIA/EIA J-STD-607-A, Commercial Building Grounding (Earthing) and Bonding Requirements for Telecommunications.39 ATIS-0600012, Electrical Protection Considerations for Broadband Systems.110 IEC 60529, Degrees of Protection

12、 Provided by Enclosures (IP Code).411 IEC 61196, Coaxial Communications Cables.412 IEEE 367, Recommended Practice for Determining the Electric Power Station Ground Potential Rise and Induced Voltage from a Power Fault.513 IEEE 487, Recommended Practice for the Protection of Wire-Line Communication F

13、acilities Serving Electric Power Locations.514 IEEE 1590, Recommended Practice for the Electrical Protection of Communication Facilities Serving Electric Supply Locations Using Optical Fiber Systems.515 ITU-T K.27, Bonding Configurations and Earthing Inside a Telecommunications Building Protection A

14、gainst Interference.616 MIL-STD-196E, Joint Electronics Type Designation System.717 MIL-C-39012, General Specification for Connectors, Coaxial, Radio Frequency.718 NEMA 250, Enclosures for Electrical Equipment (1000 Volts Maximum).819 Telcordia, GR-49, Outdoor Telephone Network Interface Devices.91T

15、his document is available from the Alliance for Telecommunications Industry Solutions, 1200 G Street N.W., Suite 500, Washington, DC 20005. 2This document is available from the National Fire Protection Association (NFPA). 3This document is available from the Telecommunications Industry Association (

16、TIA). 4This document is available from the International Electrotechnical Commission. 5This document is available from the Institute of Electrical and Electronics Engineers (IEEE). 6This document is available from the International Telecommunications Union. 7Available from the Department of Defense

17、Single Stock Point for Military Specifications and Standards, located at the Document Automation and Production Service, Building 4/D, 700 Robins Ave, Philadelphia, Pa. 19111-5094. 8This document is available from the National Electrical Manufacturers Association. ATIS-0600012.03 3 20 Telcordia, GR-

18、295, Mesh and Isolated Bonding Networks: Definition and Application to Telephone Central Offices.921 Telcordia, GR-974, Telecommunications Line Protector Units.922 Telcordia GR-1089, Electromagnetic Compatibility and Electrical Safety - Generic Criteria for Network Telecommunications Equipment.923 T

19、elcordia, GR-2908, Surge Protectors on Coaxial Lines at Customer Premises.924 Telcordia, GR-3111, Transmission Characteristics for Outside Plant Passive Copper Components.925 UL 497C, Standard for Safety Protectors for Coaxial Communications Circuits.103 Definitions, Acronyms, however, the impedance

20、 loss for DS-3 signal frequencies is relatively high. 734A cable is slightly larger, and thus its DS-3 signal loss is less. Since it is desirable to limit the cable loss to about 5 dB, the practical distance limit for DS-3 runs on 735A coaxial cable is about 60 m. For 734A cable, the typical maximum

21、 run distance is about 130 m. If longer runs are needed, solid-shield 75- characteristic CATV-type cable - such as RG-11 or QR-320 - may be used. The following table summarizes typical coaxial cables used for DS-3 outdoor transmission 11. ATIS-0600012.03 6 Table 1: Typical Outdoor DS-3 Coax Cable Pr

22、operties Cable Type Characteristic Impedance Typical Terminations Typical Attenuation for DS-3 Typical Max DS-3 Distance 735A 75 BNC 0.092 dB/m 60 m 734A 0.043 dB/m 130 m RG-11 F-type 0.023 dB/m 240 m QR-320 0.019 dB/m 300 m L1 GPS Timing signals are typically carried from the antenna to the timing

23、bays on LMR-400 coaxial cable (similar to the RG-8 16 type cable commonly used in CATV applications), and terminated with 50- N-type 17 connectors. LMR-type cables are considered to be low-loss communications cables. Because it is usually desired to limit total cable loss to approximately 30 dB for

24、most of these timing applications (cable loss may be offset by the gain of an active antenna, so actual cable loss and distance is manufacturer-specific), the typical maximum distance for an LMR-400 cable carrying GPS timing signals is about 150 m. For shorter runs, RG-59 or 734A cable is also somet

25、imes used, but they have a characteristic impedance of 75- (so the antenna and indoor termination equipment shall match that impedance). If longer runs are needed, hard-line coaxial cable types (such as QR-types or Heliax) may be used. The following table summarizes typical coaxial cables used for b

26、ringing L1 timing signals from an outdoor GPS antenna to an indoor synchronization equipment bay 11 Note that Heliax, LMR, and QR type cables are vendor-specific trademarked cable types, but other manufacturers make relatively equivalent coaxial cables that can also be used. Note also that the typic

27、al terminations shown in Tables 1 and 2 are simply typical; therefore, other termination types can be used as needed to match protector, antenna, and timing equipment input and output port needs, as long as the connectors characteristic impedance matches that of the cable, protector, and terminating

28、 equipment. ATIS-0600012.03 7 Table 2: Typical Outdoor GPS Timing Coax Cable Properties Cable Type Characteristic Impedance Typical Terminations Typical Attenuation for GPS L1 Typical Max GPS L1 Distance LMR-400 50 N-type 0.20 dB/m 150 m RG-8 TNC 0.18 dB/m 170 m LMR-100 N-type 1.02 dB/m 25 m RG-58 B

29、NC 0.65 dB/m 45 m LMR-195 N-type 0.49 dB/m 60 m LMR-200 0.44 dB/m 65 m FSJ1-50A 0.25 dB/m 120 m LDF1-50 0.18 dB/m 165 m FSJ2-50 0.17 dB/m 175 m LDF2-50 0.15 dB/m 200 m FSJ4-50B 0.15 dB/m 200 m LMR-600 0.11 dB/m 250 m LDF4-50A 0.094 dB/m 320 m LMR-900 0.076 dB/m 400 m LDF4.5-50A 0.070 dB/m 425 m LMR-

30、1200 0.057 dB/m 500 m LDF5-50A 0.054 dB/m 560 m AVA5-50 0.049 dB/m 615 m LMR-1700 0.043 dB/m 700 m LDF6-50 0.039 dB/m 775 m LDF7-50A 0.032 dB/m 930 m AVA7-50 0.029 dB/m 1020 m 734A 75 TNC 0.67 dB/m 45 m RG-59 BNC 0.48 dB/m 60 m QR-320 F-type 0.18 dB/m 160 m QR-540 0.10 dB/m 300 m LDF4-75 N-type 0.09

31、4 dB/m 320 m QR-715 F-type 0.073 dB/m 400 m QR-860 0.067 dB/m 450 m 5 Coaxial DS-3 however, protectors that pass bandwidths from 0-50 MHz with insertion losses of less than 0.2 dB over that frequency range are acceptable. Typical protectors used for GPS coax protection pass analog bandwidths ranging

32、 from 0 to more than 3 GHz, although they probably only need to pass frequencies between 1 and 2 GHz with an insertion loss of less than 0.5 dB. 5.2 Choosing the Appropriate Clamping Voltage Because no appreciable voltage or current is carried in a DS-3 or GPS timing signal over coax, the choice of

33、clamping voltage is not dependent on the signal voltages. Instead, the choice of protector clamping voltage should be based on the withstand capabilities of the equipment being protected. If the equipment being protected has been tested to withstand surges on the coaxial port of up to 700 V, a surge

34、 protector with clamping voltages of 400 V may be sufficient (protection coordination so the primary protector fires first). Choosing too low of a clamping voltage (for example, below 60 V) for this application may lead to nuisance operation of the surge arrestor, thus interrupting service when it d

35、oes not need to be interrupted. In addition gas tubes with lower clamping voltages typically have slower response times. Breakdown (clamping) voltages for commercially available DS-3 protectors vary widely (from as low as 10 V to more than 700 V). Breakdown voltages for typical GPS protectors also v

36、ary widely (from as lows as 10 V to more than 200 V). A breakdown voltage for either a DS-3 or GPS protector in the 60 to 150 V range (a typical choice is 90 V) may be a good compromise between nuisance operations, response time, and equipment protection when the secondary protection characteristics

37、 of the DS-3 NIU or equipment timing (sync) bay are not known or are non-existent (a lot of existing equipment never had the coax ports tested for surge protection because they werent expected to support metallic facilities that ran outdoors). 5.3 Additional Protector Testing Considerations The surg

38、e arrestor should safely limit expected surge voltages (between the center conductor and the outer shield) and safely conduct expected surge currents (i.e., be Listed to a relevant standard, such as UL 497C). The surge protector should have the ability to repeatedly conduct commonly occurring surges

39、 without causing a permanent service interruption, and it shall have a fail-safe mode for extreme surges. The surge arrestor may also perform the function of grounding the shield of the coaxial cable (grounding of the shield is required by NEC 6 Articles 820.100 and 830.93). Because the DS-3 and GPS

40、 coaxial runs discussed herein are not normally current-carrying, the surge arrestor used does not have to be internally fused, but that does not preclude the use of internally fused arrestors. The surge arrestor may be rated for use in a NEMA-type enclosure or NID, or may be rated to be exposed to

41、the elements. It shall be applied according to its ratings and Listing. Because of the outdoor application, the surge arrestor should be rated for operation from at least -40 to +65 C (protectors not rated for fluctuating outdoor temperatures will need to be installed indoors, but as close to the po

42、int of entry and building main grounding point as possible see Section 6.2). 5.4 When Coax Protectors for DS-3 however, it is something to be aware of. 6 Grounding 6.1 Site Grounding Proper site grounding and bonding is essential to the proper operation of any surge arrestor, and for the effectivene

43、ss of shield grounding. The grounding electrode conductor from the surge arrestor(s) and/or shield ground(s) shall not be separately grounded to its own stand-alone ground rod (per NEC Articles 250.50 and 820.100, all grounding electrodes for a site shall be bonded together). Note that if a new grou

44、nd rod is driven for the discharge ground for the surge arrestor, it shall be bonded to the other grounding electrodes for the site (even if there are multiple owners of the various grounding electrodes). If the existing grounding electrode system cannot be accessed externally (for example, it is bu

45、ried under a parking lot), it is permissible to bring the grounding electrode conductor from the discharge ground point of the surge arrestor (or the new ground rod) to a point on the exterior wall close to the site building/cabinet main grounding bus (alternately known as a BPG 2, OPGP 20, TMGB 8,

46、PANI bar, Main Earthing Terminal 15, Master Ground Bar 3, etc. ), bring it through the wall or an entrance conduit, and connect it to the main grounding bus right there so that any lightning or surges brought into the site will immediately go back out to earth through the grounding electrodes alread

47、y connected to the main grounding bus. 6.2 Surge Suppressor and Shield Ground Location For most instances where coaxial cable carrying DS-3 or GPS timing signals is run outdoors, surge suppression should be installed at building or cabinet entrances/exits (the demarc), with the “ground” of the surge

48、 suppressor connected to the site grounding electrode system. The user will want to avoid bringing surges and lightning into the building or cabinet as much as possible. Therefore, they will want to locate the surge suppressor (and/or shield grounds) as close to the point of coaxial cable entry/exit

49、 into the building or cabinet as is feasible (see NEC Article 830.100B), and keep the surge arrestor and its grounding electrode conductor outdoors if they can. For roof-mounted antennae, if the coax cable entrance is also on the roof and the roof is equipped with a lightning protection system (such as an NFPA 780 Franklin rod system), the surge arrestor should be mounted as close as possible (preferably outside) to the entrance port (in some cases it is a bulkhead-mount arr