ANSI ATIS 0600316-2008 Electrical Protection of Telecommunications Outside Plant.pdf

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1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0600316.2008 ELECTRICAL PROTECTION OF TELECOMMUNICATIONS OUTSIDE PLANT ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven standards for the information, ente

2、rtainment and communications industry. More than 200 companies actively formulate standards in ATIS 17 Committees, covering issues including: IPTV, Cloud Services, Energy Efficiency, IP-Based and Wireless Technologies, Quality of Service, Billing and Operational Support, Emergency Services, Architec

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4、ational 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 accredited by the American

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11、onal Standards Institute. Notice of Disclaimer b) Contact with electric power circuits; c) GPR (Ground Potential Rise); or d) Induction from electric power lines. 5.1.1 Lightning disturbances Lightning can create disturbances to the telecommunications outside plant facilities by either a direct stri

12、ke to the facility itself or by a strike near the facility. Some of the lightnings electromagnetic energy could also be coupled to the power wires or to the cables carrying telecommunications signals. 5.1.2 Contact with power circuits Power and telecommunications companies often serve the same custo

13、mers and frequently employ joint-use, or common, outside plant facilities such as poles for aerial plant or a common trench for buried plant. Clearances and separations for joint-use facilities are regulated by either ANSI C2 or local codes. Power contact may result from a falling phase conductor in

14、 aerial plant or a dig-in in buried plant. 5.1.3 Ground potential rise (GPR) due to power influence During normal conditions the power systems grounded neutral conductor is at the same potential as remote earth. Ground potential rise occurs during a power fault when the fault current returns to its

15、source through the earth. During fault conditions the potential at the local ground of the telecommunications outside plant facilities rises with respect to remote earth. 5.1.3.1 Ground potential rise (GPR) due to Lightning Influence A ground potential rise can occur at cell sites as a result of lig

16、htning striking a cell tower, a nearby structure, or earth ground. The lightning current radiates outwardly from the strike point. The resulting current flow through the ground impedance creates potential differences between various points surrounding the site that was struck. Communication systems,

17、 which are grounded at different points, can experience short duration potential differences resulting in large current flow that can damage tip/ring and power circuits with ground references. 5.1.4 Induction from power lines Power and telecommunications outside plant facilities frequently occupy jo

18、int structures or a common right-of-way, and as such, occupy parallel routes. The proximity of power and telecommunications outside plant facilities can result in voltages being induced on the telecommunications metallic facilities, by either magnetic or electric fields. 5.1.4.1 Magnetic field induc

19、tion The magnetic field produced by currents in a nearby power line may result in large voltages being introduced into the telecommunications outside plant through inductive coupling, especially under conditions on the power facility such as a phase-to-neutral fault. 5.1.4.2 Electric field induction

20、 Ungrounded telecommunications outside plant, hardware, and personnel located in the vicinity of extra high voltage (EHV) power transmission lines (greater than 300 kV, phase-to-phase) may become electrically energized by electric coupling to the EHV power line. An ungrounded object, including a per

21、son, will assume a potential relative to the earth, based upon the power line voltage and geometry, ATIS-0600316.2008 5 and the capacitance of the object or person with respect to both the power line and the earth. Personnel working near higher voltage lines (approximately 125 kV and greater) may be

22、come charged by the electric field surrounding the lines. The induced voltages can be quite large and the available current is usually quite small, below the level that may cause electrical injury. However, the electric shock or arc obtained may be startling, causing accidental injury as a result of

23、 involuntary reaction. Grounding of telecommunications plant and hardware helps to minimize the possibility for injury due to involuntary reactions by keeping the cables and hardware and the earth near them at the same potential. 5.2 Classification of exposure of outside plant 5.2.1 General exposure

24、 considerations The decision to classify a particular outside plant facility as exposed involves judgment. The physical characteristics of the outside plant must be considered (i.e., does a cable contain metallic members or metallic communications conductors?). Previous experience in a particular ge

25、ographical area may also help determine the electrical protection required. For example, where outside plant facilities are exposed to lightning, previous experience may be useful in coordinating cable dielectric breakdown voltage. An individual segment of outside plant may itself be unexposed to li

26、ghtning or power, but through exposure of laterals connecting to that segment, it too should be classified as exposed. The effects of future rearrangements should also be considered when determining the exposure status of outside plant. Any telecommunications outside plant facility that is classifie

27、d as exposed shall require coordinated electrical protection. Generally OSP equipment interfaces (ports) and associated wiring/cabling for the interconnection of equipment of the same installation and the interfaces/ports separated by a distance of 20 meters or less are not considered exposed. The c

28、ustomer side interfaces and wiring of NIDS, which are isolated from the outside plant wiring system, are also not considered exposed. 5.2.2 Exposure to lightning A telecommunications outside plant facility shall be classified as exposed to lightning unless the ground flash density is an average of 0

29、.3 flashes/km2per year or fewer and earth resistivity of less than 100 ohm-meters as measured per ANSI/IEEE 81 (Guide for Measuring Earth Resistivity, Ground Impedance, and Earth Surface Potentials of a Ground System, Part 1 Normal Measurements). Telecommunications outside plant facilities shall be

30、classified as exposed if they serve any location that is classified as exposed to lightning. 5.2.3 Exposure to power contact Telecommunications outside plant facilities shall be considered exposed to power contact when the possibility exists for contacting a power conductor operating at 300 volts rm

31、s to ground (earth). 5.2.4 Exposure to GPR A telecommunications outside plant facility shall be considered exposed to GPR if the possibility exists that local ground may differ from remote earth by 300 volts rms as determined by methods presented in ANSI/IEEE 367. 5.2.5 Exposure to power induction A

32、 telecommunications outside plant facility shall be considered exposed to power fault induction when the possibility for induced voltages in excess of 300 volts rms to ground exists as determined by methods presented in ANSI/IEEE 367 or ANSI/IEEE 776. ATIS-0600316.2008 6 5.2.6 Aerial plant Aerial ou

33、tside plant is almost always exposed to lightning. Only a few geographical areas qualify as non-lightning areas (see 5.2.2). Telecommunications outside plant may be classified as unexposed to lightning if it is located in an area treated as unexposed by the owning utility. Such an area may be a metr

34、opolitan or urban location having a high density of multistory buildings and an extensive network of buried metallic piping systems and cables. In these areas, the telecommunications outside plant is effectively shielded from lightning-induced surges. However, aerial construction is seldom used in m

35、etropolitan areas. Aerial outside plant should be considered exposed to power, even if power is not present, since there is no assurance that power conductors will not be placed at a later time. Aerial outside plant is generally considered exposed to power unless confined within a block as defined i

36、n ANSI/NFPA 70. Aerial outside plant containing no metallic members, metallic communications conductors, or metallic support messenger, such as all-dielectric optical fiber cable and dielectric support messenger, is considered unexposed to lightning and power. 5.2.7 Buried plant Buried plant is subj

37、ect to exposure to lightning. Outside plant is not safe from lightning solely because it is buried below the earths surface. A buried telecommunications cable or wire can become a conductor of lightning currents resulting from nearby strokes to the earth. In addition, in locations exposed to lightni

38、ng, buried optical fiber cables, including all-dielectric cables, might be subject to crushing damage due to arcing of lightning to nearby objects. Inter-building cable runs of 140 feet 42.7 m or less, directly buried or in underground conduit where a continuous metallic cable shield or a continuous

39、 metallic conduit containing the cable is bonded to each building grounding electrode system should be considered as unexposed to lightning. Examples are campus environments and short inter-building cables. Joint random buried plant is considered to be exposed to power contact. Even though considere

40、d unexposed to power contact, buried telecommunications plant that parallels power conductors for long distances is subject to power fault induction and - regardless of parallel distance - is subject to ground potential rise resulting from power faults and should be classified as exposed. 5.2.8 Unde

41、rground plant In metropolitan areas, underground plant is usually not exposed to lightning because of the shielding effects of tall buildings and buried metallic pipe systems. Underground plant is exposed to lightning in rural and suburban areas unless the plant is located where low incidence of thu

42、nderstorms and low ground resistivity prevail. Underground construction methods, by design, help to eliminate the possibility of power contacts, but not exposure to power fault induction and ground potential rise. 5.2.9 Bridges, overpasses, submarine plant The exposure classification of cable in con

43、duit on bridges and overpasses is considered to be that of underground cable. Cable mounted on bridge supports is treated as aerial cable. Submarine cable is regarded as buried cable. ATIS-0600316.2008 7 6 Electrical protection measures 6.1 General protection measures Electrical protection measures

44、for telecommunications outside plant include maintenance of shield and other metallic member continuity on cable and wire, and bonding and grounding of metallic members and support strands where present. Proper physical separation between joint-use utilities (e.g., power, telephone, cable television

45、 on the same pole) should also be maintained. Cable protectors may be applied where cable facilities are exposed to lightning and certain types of internal cable construction may be selected for specific applications based upon lightning experience and cable dielectric coordination considerations. W

46、ire protectors may be applied where wire is exposed to contact with power voltages. Fuse links that coordinate with the current-handling capability of telephone protectors placed at telephone central offices and customer premises may also be required where the outside plant is exposed to power. Some

47、 electrical environments are unique, such as occur at a power station, power substation, cell site, or near a high voltage transmission line structure during a power fault, and require special consideration. 6.2 Separations and clearances Physical separation between utilities such as power and telep

48、hone occupying joint-use structures such as poles, are intended to provide for the safety of utility personnel as well as the telephone customer. The requirements for separations between utilities occupying joint structures are contained in ANSI C2. 6.3 Bonding and grounding Low-impedance paths to g

49、round are effective in mitigating damage to telecommunications outside plant from both lightning and ac power faults. When telephone outside plant is run jointly with Multi-Grounded Neutral (MGN) power, the MGN is usually the lowest impedance path to ground available. Bonding of metallic members and support strands to the MGN serves to remove lightning currents as rapidly as possible from the telecommunications facilities, minimizing the amount of telecommunications outside plant damaged in a lightning event. In the event of a power contact, bonding to the MGN provides a low imped