ATIS 0600012 03-2017 Electrical Protection Considerations for Outdoor Coaxial Cable Runs for DS-3 and GPS Timing Signals.pdf

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1、 ATIS-0600012.03 ATIS Standard on - Electrical Protection Considerations for Outdoor Coaxial Cable Runs for DS-3 and GPS Timing Signals As a leading technology and solutions development organization, the Alliance for Telecommunications Industry Solutions (ATIS) brings together the top global ICT com

2、panies to advance the industrys most pressing business priorities. ATIS nearly 200 member companies are currently working to address the All-IP transition, 5G, network functions virtualization, big data analytics, cloud services, device solutions, emergency services, M2M, cyber security, network evo

3、lution, quality of service, billing support, operations, and much more. These priorities follow a fast-track development lifecycle from design and innovation through standards, specifications, requirements, business use cases, software toolkits, open source solutions, and interoperability testing. A

4、TIS is accredited by the American National Standards Institute (ANSI). The organization is the North American Organizational Partner for the 3rd Generation Partnership Project (3GPP), a founding Partner of the oneM2M global initiative, a member of the International Telecommunication Union (ITU), as

5、well as a member of the Inter-American Telecommunication Commission (CITEL). For more information, visit www.atis.org. 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

6、-59, RG-8, etc. relatively long run (thus more subject to EMI influence) coaxial cable plant with network-powered repeaters. While most of the test procedures of GR-290812 are applicable, this document intends to provide additional application guidance for outdoor DS-3 and GPS signals over 734A, 735

7、A, low loss communications 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) non-repeatered runs. 2 References The following standards contain provisions which, through referenced in this text, constitute

8、provisions of this ATIS Standard. At the time of publication, the editions indicated were valid (where no edition is indicated, the latest edition ATIS-0600012.03 2 applies). All standards are subject to revision, and parties to agreements based on this ATIS Standard are encouraged to investigate th

9、e possibility of applying the most recent editions of the standards indicated below. As references are added to the documents, they are added to the end of the respective reference list using the next sequential reference number. Normative references are numbered 1-99 and informative references (Bib

10、liography) are numbered starting from 101 in order to distinguish the type of reference based on the number. 1 ATIS-0100510, Network Performance Parameters for Dedicated Digital Services for Rates up to and Including DS3 Specifications.12 ATIS-0900101, Synchronization Interface Standard.13 NFPA 70,

11、National Electrical Code(NEC).24 NFPA 780, Installation of Lightning Protection Systems.25 ATIS-0600012, Electrical Protection Considerations for Broadband Systems.16 IEC 61196, Coaxial Communications Cables.37 IEEE 367, Recommended Practice for Determining the Electric Power Station Ground Potentia

12、l Rise and Induced Voltage from a Power Fault.48 IEEE 487, Recommended Practice for the Protection of Wire-Line Communication Facilities Serving Electric Power Locations.49 IEEE 1590, Recommended Practice for the Electrical Protection of Communication Facilities Serving Electric Supply Locations Usi

13、ng Optical Fiber Systems.410 Telcordia GR-974, Telecommunications Line Protector Units.511 Telcordia GR-1089, Electromagnetic Compatibility and Electrical Safety - Generic Criteria for Network Telecommunications Equipment.512 Telcordia GR-2908, Surge Protectors on Coaxial Lines at Customer Premises.

14、513 Telcordia GR-3111, Transmission Characteristics for Outside Plant Passive Copper Components.514 UL 497C, Standard for Safety Protectors for Coaxial Communications Circuits.63 Definitions, Acronyms, however, the impedance loss for DS-3 signal frequencies is relatively high. 734A cable is slightly

15、 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 run distance is about 130 m. If longer runs are needed, solid-shield 75- ch

16、aracteristic 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 (IEC 61196, Coaxial Communications Cables 6). Table 4.1: Typical Outdoor DS-3 Coax Cable Properties Cable Type Characteristic Impedance Typical T

17、erminations 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 bays on LMR-400 coaxial cable (similar to the RG-8 typ

18、e cable commonly used in CATV applications), and terminated with 50- N-type connectors (MIL-C-39012, General Specification for Connectors, Coaxial, Radio Frequency 17). LMR-type cables are considered to be low-loss communications cables. Because it is usually desired to limit total cable loss to app

19、roximately 30 dB for 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 734

20、A cable is also sometimes 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 coax

21、ial cables used for bringing L1 timing signals from an outdoor GPS antenna to an indoor synchronization equipment bay (IEC 61196 6). ATIS-0600012.03 6 Note that Heliax, LMR, and QR type cables are vendor-specific trademarked cable types, but other manufacturers make relatively equivalent coaxial cab

22、les that can also be used. Note also that the typical terminations shown in Tables 4.1 and 4.2 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 impedanc

23、e matches that of the cable, protector, and terminating equipment. Table 4.2: 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

24、m LMR-100 N-type 1.02 dB/m 25 m RG-58 BNC 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

25、 400 m LDF4.5-50A 0.070 dB/m 425 m LMR-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-

26、540 0.10 dB/m 300 m LDF4-75 N-type 0.094 dB/m 320 m QR-715 F-type 0.073 dB/m 400 m QR-860 0.067 dB/m 450 m ATIS-0600012.03 7 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 us

27、ed for GPS coax protection pass analog bandwidths ranging 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

28、 in a DS-3 or GPS timing signal over coax, the choice of 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 wit

29、hstand surges on the coaxial port of up to 700 V, a surge 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 o

30、f the surge arrestor, thus interrupting service when it does 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

31、 V). Breakdown voltages for typical GPS protectors also vary 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

32、 protection when the secondary protection characteristics 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).

33、 5.3 Additional Protector Testing Considerations The surge 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 14). The surge protector should have

34、 the ability to repeatedly conduct commonly occurring surges 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

35、NEC3 ATIS-0600012.03 8 Articles 820.100 and 830.93). Because the DS-3 and GPS 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 rat

36、ed for use in a NEMA-type enclosure or NID, or may be rated to be exposed to 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 o

37、utdoor temperatures will need to be installed indoors, but as close to the point 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 ess

38、ential to the proper operation of any surge arrestor, and for the effectiveness 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 NECArticles 250.50 and 820.100, all ground

39、ing electrodes for a site shall be bonded together 3). Note that if a new ground 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 g

40、rounding electrode system cannot be accessed externally (for example, it is buried 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 buildi

41、ng/cabinet main grounding bus (alternately known as a BPG, OPGP, TMGB, PANI bar, Main Earthing Terminal, Master Ground Bar, 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 immedia

42、tely go back out to earth through the grounding electrodes already connected to the main grounding bus. ATIS-0600012.03 9 6.2 Surge Suppressor & 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

43、 building or cabinet entrances/exits (the demarc), with the “ground” of the surge 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 sup

44、pressor (and/or shield grounds) as close to the point of coaxial cable entry/exit into the building or cabinet as is feasible (see NEC Article 830.100B 3), and keep the surge arrestor and its grounding electrode conductor outdoors if they can. For roof-mounted antennae, if the coax cable entrance is

45、 also on the roof and the roof is equipped with a lightning protection system (such as an NFPA 780 4 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 arrestor making metal-to-metal contact

46、with the waveguide hatchplate, and you cannot get any closer to the waveguide entry than that), and then bonded to the nearest rooftop lightning protection system conductor. If there is no rooftop lightning protection system, or if the local Authority Having Jurisdiction (AHJ) does not allow connect

47、ion of surge arrestors on the roof to the lightning protection system, run a downleader from the ground discharge terminal of the arrestor across the roof and down the side of the building, connecting it to the existing ground electrode field for the building. If the entrance of the coax is on the s

48、ide of the structure however, it is best to bond the surge-arrestor discharge ground to the grounding electrode system. If that system cannot be accessed externally, but there is an NFPA 780 Lightning Protection System 4 (LPS) termination devices, main conductor, and grounding electrodes entering th

49、e earth, because it is supposed to be bonded to any other site grounding electrode systems, it is permissible to bond to the main conductor at ground level (it is impermissible to bond to it higher up), and a separation of several feet (see the formula in Section 4.21 of NFPA 780 4 for an exact calculation of the minimum spacing) is required between the surge arrestor discharge ground electrode conductor coming down the side of the building and the main conductor until ground level is reached.