1、IEEE Std 1590-2009(Revision ofIEEE Std 1590-2003)IEEE Recommended Practice for theElectrical Protection ofCommunication Facilities ServingElectric Supply Locations UsingOptical Fiber SystemsIEEE3 Park Avenue New York, NY 10016-5997, USA26 June 2009IEEE Power +1 978 750 8400. Permission to photocopy
2、portions of any individual standard for educational classroom use can also be obtained through the Copyright Clearance Center. IntroductionThis introduction is not part of IEEE Std 1590-2009, IEEE Recommended Practice for the Electrical Protection of Communication Facilities Serving Electric Supply
3、Locations Using Optical Fiber Systems. Some electrical environments, collectively called electric supply locations, require the application of unique electrical protection techniques because of their special nature. One such environment is the electric power station or substation. Another is at, or
4、near, power line transmission and distribution structures such as towers or poles. Such structures often provide a convenient site for the location of wireless, personal communications service, and cellular antennas and their associated electronic equipment that is served by a link to the wired tele
5、communications network. IEEE Std 487-2007aprovides additional details on these locations. This recommended practice assumes that optical fiber cables are to be used to provide electrical isolation for telecommunications services to these electric supply locations. Refer to IEEE Std 367-1996 or IEEE
6、Std 487-2007. This recommended practice describes applications consisting entirely of fiber and applications where both metallic cables and fiber cables are used. In the latter case, i.e., hybrid applications, the user is referred to IEEE Std 487-2007 for the metallic portion of the application. Som
7、e delays in site activation often occur due to the time involved in obtaining electrical information data for most high-voltage tower or pole sites. The delays may be eliminated by using the fiber optical solutions described in this recommended practice. This recommended practice has been prepared b
8、y the Wireline Working Group of the Power System Communications Committee of the IEEE Power this overhead grounding system will reduce ground return current at individual towers and reduce clearing time of the fault by providing a more direct path to operate relays. These systems follow many differe
9、nt protection designs, from being grounded at each tower and the substations to being insulated with a 3 to 5 kV spark gap device at every tower or every fourth tower. They may be stopped two to four spans before the substation or extend from the substation three to four spans only to protect the su
10、bstation alone. In low lightning areas, they may not exist at all, and each tower is left to stand on its own. The net effect of the overhead grounding system is to reduce the ground return current at individual towers by providing multiple discharge paths. This, in turn, reduces the current flowing
11、 through the ground grid reduces clearing time, and lowers fault-produced GPR to manageable levels. Typical grounding requirements for BTS Several documents, such as R56B B32, are in general use in the wireless industry. These documents provide minimum grounding requirements, along with site prepara
12、tion recommendations, necessary to meet personnel safety and warranty conditions from the equipment vendors or manufacturers. These documents tend to recommend low ground impedances for 50 to 60 Hz power as well as lightning frequencies at the sites. When the sites are located at, or near, power lin
13、e transmission and distribution structures such as towers or poles, enhancements of the ground field may be necessary to meet these requirements to reduce step, touch, and mesh voltages. As a reminder, and for the purposes of this recommended practice, mesh voltage is the maximum touch voltage to be
14、 found within a mesh of a ground grid; step voltage is the difference in surface potential experienced by a person bridging a distance of 1 m (3 ft) with his or her feet without contacting any other grounded object; and touch voltage is the potential difference between the GPR and the surface potent
15、ial at the point where a person is standing, while at the same time having his or her hands in contact with a grounded structure.1313Taken from IEEE Std 80-2000. 16Copyright 2009 IEEE. All rights reserved. IEEE Std 1590-2009 IEEE Recommended Practice for the Electrical Protection of Communication Fa
16、cilities Serving Electric Supply Locations Using Optical Fiber Systems 8.6.4 Step, touch, and mesh voltages for BTSs located on power line transmission or distribution structures Lightning and 50 to 60 Hz fault currents for BTSs located on a high-voltage transmission structures can flow on three pre
17、dominant conducting paths back to their source(s) within the power grid. The first path is the tower sky wire system (when used) grounded to earth and near tower groundings in, on, or adjacent to the lines right of way (ROW). The second path is the tower and BTS combined grounding system. The third
18、path is through the local power system ground that provides power to the site. Figure 5 depicts these current distribution paths (see Grcev et al. B11 and B13). ACPOWERBTSRADIOSKYWIRESLIGHTNINGSTRIKENOTEReprinted with permission from Grcev et al. B11.Figure 5 Possible lightning current distributions
19、 for a BTS on a power tower The distribution, or current magnitude on the various paths, becomes a function of the path impedance at the various fault frequencies. The frequency and fault current path relationships are shown in Figure 6.According to Grcev et al. B11, B12, and B13, at the fundamental
20、 50 to 60 Hz power frequencies the sky wires conduct approximately 60% of the fault current while the tower/BTS grounding system conducts less that 10% to remote earth (low-frequency GPR). The remaining current follows the local ac power grounding network and distributes it throughout the community
21、(see Rajotte et al. B33). At lightning frequencies approaching 10 to 100 kHz, the inductive characteristic of the sky wires and local power present higher impedances, while the tower presents a lower impedance to ground and conducts over 90% of lightning fault currents (high-frequency GPR). 17Copyri
22、ght 2009 IEEE. All rights reserved. IEEE Std 1590-2009 IEEE Recommended Practice for the Electrical Protection of Communication Facilities Serving Electric Supply Locations Using Optical Fiber Systems MAGNITUDE OFCURRENT(%)FREQUENCY (Hz)1001008060402001k 10k 100k 1e+6SKY WIRESTOWERGROUNDSLV-MVPOWER5
23、0-60HzNOTEReprinted with permission from Grcev et al. B12.Figure 6 Current distribution between sky wires, tower grounds, and local power These current flow relationships present an abundance of step, touch, and mesh voltages at the site during low- and/or high-frequency fault conditions. To promote
24、 worker safety and to reduce equipment electrical failures, the recommendations of Figure 7 provide various means of reducing these hazardous voltage levels. 1PWRBTSOEI362POWERTRANSMISSIONTOWER7CONCRETE PAD,ELEVATEDMETALLICPLATFORM,OR STANDALONE BUILDING98ICEBRIDGE1114GATEWIRE MESHSAFETY MATSECURITY
25、 FENCE5101010GRAVELFILLPVCENTRANCECONDUITS10BULKHEADFigure 7 Bonding and grounding recommendations for power tower installations 18Copyright 2009 IEEE. All rights reserved. IEEE Std 1590-2009 IEEE Recommended Practice for the Electrical Protection of Communication Facilities Serving Electric Supply
26、Locations Using Optical Fiber Systems The following notes relate to the small numbered diamonds within Figure 7.1 Joint use power transmission towers, At these specific locations, it is recommended that an additional 2 AWG bare solid tinned copper wire ground ring be placed at a 0.3 m (24 in) depth
27、and bonded to each tower leg with a listed bond. If a counterpoise is required due to poor soil resistivity, extend a 2 AWG solid tinned wire approximately 10 to 15 m (30 to 50 ft) from each corner with ground rods (if possible) placed at each end and at 6 m (20 ft) spacings. The recommended depth o
28、f the counterpoise wire is 0.6 m (24 in) and shall not contact any other metallic components at the site (i.e., fences). This setup will reduce touch and step potential. 2 Ice bridge bond. When the BTS radio is placed to the side of the power tower (as shown in Figure 7), the ice bridge should not b
29、e bonded to the tower structure. It should be bonded only at the bulkhead for equalization purposes. This setup will reduce touch and step potential. 3 BTS grounding ring. Place a 2 AWG bare solid tinned copper wire within 1 m (3 ft) 15% tolerance from edge of the concrete pad, elevated metallic pla
30、tform, or building at a maximum depth of 0.6 m (2 ft). Ground rods should be placed a minimum of 3 m (10 ft) apart and/or at each corner of the ground ring. This setup will reduce touch and step potential when the ring is bonded to the mat in note 4. 4 Wire mesh safety mat. It is recommended at join
31、t-use power towers that a wire mesh safety mat 150 mm (6 in) on center be bonded to the ground ring and extended a minimum of 3 m (6 ft) from the edge of the pad or power tower foot print, whichever is the greatest distance. This setup will reduce touch, step, and mesh potential when covered with gr
32、avel fill as described in note 5.5 Gravel fill, To promote worker safety and to decrease step potential, a layer of clean crushed gravel a minimum of 75 to 150 mm (3 to 6 in) deep should be placed over the entire grid/mesh area. When a security fence is in place, the clean crushed gravel should be p
33、laced within the total security fence area. See IEEE Std 80-2000 for design details. For worker safety, do not use conductive asphalt for this application as conductive asphalt will increase touch and step potential. 6 Bulkhead ground bar. The bulkhead is the single-point ground for the installation
34、. All equipment or secondary protectors that require a ground or ground reference shall be bonded to this single point, either directly or with the use of a master ground bar located within 1 m (3 ft) of the bulkhead. Use individual listed grounding kits for each coax cable entering the BTS at this
35、location. This setup will reduce touch and step potential for workers and provide voltage equalization for equipment at the site. 7 Concrete pad, elevated metallic platform, or stand alone building. If a concrete pad contains rebar and/or wire mesh, it shall be equipped with external bonding connect
36、ors and bonded to the ground ring at a minimum of two opposing corners. If the BTS is placed on an elevated metallic platform or stand-alone building, it should also be bonded to the ground ring at a minimum of two opposing corners. The bonding wires should be a minimum 6 AWG copper wire. This setup
37、 will reduce touch, step, and mesh potential and provide voltage equalization for equipment at the site. 8 AC power entrance panel. Commercial ac power service entrance cables should be placed in a polyvinyl chloride (PVC) conduit (suitable for power cable pulling) at a minimum depth of 1 m (3 ft) t
38、o a point beyond the power corridor (ROW). The entrance panel should be bonded directly to the ground ring at its closest location. If properly installed, the BTS ring ground meets or exceeds the NEC Article 250 utility protection ground. If local codes require an additional ground rod, bond the gro
39、und rod to the ground ring. All power circuits that enter the BTS shall be provided with primary protection (placed on the line side of the serving panel board) and secondary protection (placed on the load side of each 20 A circuit). Some manufacturers provide secondary protection within their equip
40、ment that meets the secondary requirement. All secondary green wire safety conductors should be placed within 1 m (3 ft) of, and bonded to, the bulkhead or master ground bar with a copper conductor sized per NEC Article 250-122. 19Copyright 2009 IEEE. All rights reserved. IEEE Std 1590-2009 IEEE Rec
41、ommended Practice for the Electrical Protection of Communication Facilities Serving Electric Supply Locations Using Optical Fiber Systems 9.9.19.29 High-voltage protection (HVP). Optical fiber cables should be placed in a PVC conduit (suitable for communication cable pulling) at a minimum depth of 0
42、.6 m (2 ft) to a point beyond the power corridor (ROW). Secondary protectors on the station side of the optical equipment interface (OEI) and at the BTS shall be placed directly on, or bonded within 1 m (3 ft) of, the bulkhead. This setup will reduce touch potential. 10 Fence and gate equalization b
43、onds. Use 2 AWG solid tinned copper wire exothermically welded to the ground ring and attached to each inside or outside corner fence post, and or gate post, with a listed wire clamp. Place at a minimum 0.3 m (12 in) depth. Wherever practical, due to magnetic coupling with the tower counterpoise wir
44、es (if used), cross at a 90 angle while maintaining a minimum 0.3 m (12 in) vertical separation. Do not bond these two grounding systems together at crossings. Place a 2 AWG solid tinned copper wire attached to each gate post with a listed wire clamp. Place a flexible bonding strap from each gate po
45、st to the movable gate section(s) with listed clamps. If the metallic posts are not set in concrete, place an additional ground rod at each post location. This setup will reduce touch potential. Telecommunications service to electric supply locationsrecommendationsThe use of all-dielectric optical f
46、iber cables is the preferred solution since it solves some of the problems of providing protection at electric supply locations. Special protection considerations pertaining to fiber optical systems serving electric supply locations are primarily a function of the presence or absence of metallic mem
47、bers in the optical fiber cable, conduits, or locating systems. The use of all-dielectric optical fiber cable provides immunity from the effects of fault-produced GPR and induction at the electric supply location. The use of optical fiber cable containing metallic strength members, a metallic foil v
48、apor barrier, or talk pairs is not recommended within the ZOI because it raises protection considerations relating to the following: GPR Induction GPR-related protection considerations In the case where an optical fiber cable is employed between the electric supply location and the edge of the ZOI,
49、the metallic elements of the cable shall be isolated from the electric supply location ground and grounds within the ZOI. This isolation is necessary to prevent the fault-produced GPR from being introduced directly onto the metallic components. An intentional low-impedance ground connection to the metallic components will allow potentially damaging currents to flow on the cable from the grounded point to remote earth at times of power faults. When the optical fiber cable traverses the GPR ZOI, it should have sufficient
