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Regulations on lightning protection operation management of power system communication station DL 548-94

People's Republic of China (PRC) electric power industry standard

Implementation1994-11-01

People's Republic of China (PRC) and national electric power industry standard DL-548-94 issued by People's Republic of China (PRC) and Ministry of Electric Power Industry. Lightning overvoltage and electromagnetic interference protection of power system communication stations (facilities) is an important technical means to protect communication lines, equipment and personal safety and ensure the operation rate of communication lines and equipment. 1.2 the purpose of this regulation is to elaborate the technical standards and measures for lightning protection of communication stations in power system (see appendix a), operation and maintenance management system, clarify responsibilities, and take effective technical measures to continuously improve the lightning protection operation level of communication stations. 1.3 this procedure is applicable to the construction, operation, maintenance and management of lightning protection system in power system communication station. 1.4 this regulation is an integral part of the electric power industry regulations, and all units shall comply with it.

2 management principles and responsibilities

2. 1 Management Principle 2. 1. 1 The lightning protection work of power system communication stations should be managed at different levels under the leadership of the Ministry, network bureau, provincial bureau, regional bureau and county bureau (institute). The competent communication departments at all levels are the competent lightning protection departments of communication stations within their respective jurisdictions. 2. 1.2 communication departments at all levels should set up lightning protection leaders, which should generally be the leaders in charge of communication. 2. 1.3 communication departments at all levels should set up engineers (technicians) who are specially responsible for lightning protection. 2. 1.4 The communication station shall be equipped with special lightning protection personnel to do a good job in lightning protection of this station. 2. 1.5 lightning protection engineers (or technicians) and lightning protection commissioners should be communication professionals who have been trained in lightning protection technology and have certain knowledge of lightning protection. 2.2 Responsibilities of lightning protection departments at all levels 2.2. 1 Carry out communication lightning protection laws, regulations and relevant technical measures issued by superiors, and formulate corresponding communication lightning protection laws and measures in combination with the actual scope under their jurisdiction. 2.2.2 Be responsible for preparing the communication lightning protection work plan, and organize the implementation after being approved by the corresponding competent department. 2.2.3 Be responsible for the lightning protection design review, lightning protection project construction inspection and completion acceptance review of newly built, rebuilt, expanded and co-built communication stations within the jurisdiction. 2.2.4 Guide and coordinate the lightning protection work of communication stations under its jurisdiction, assign tasks, and supervise and inspect the lightning protection work of each station. 2.2.5 Be responsible for lightning protection operation statistics, lightning damage investigation and analysis of communication stations under its jurisdiction, and report statistical reports step by step. 2.2.6 Organize lightning protection technical training, experience exchange and technical research, and actively adopt and popularize advanced and practical new technologies.

3. Operation and maintenance 3. 1 Before the thunderstorm season every year, the grounding system should be inspected and maintained, mainly to check whether the connector is fastened, whether the contact is good, whether the grounding down lead is corroded, and whether the ground near the grounding body is abnormal. If necessary, the ground should be dug up, and the corrosion of underground hidden parts should be checked randomly. If problems are found, they should be handled in time.

3.2 The grounding resistance of grounding grid shall be measured once a year. See appendix b for the measurement method. The measuring instrument shall be a digital grounding resistance measuring instrument. 3.3 Before the thunderstorm season every year, the lightning protection components in operation should be tested once. During the thunderstorm season, the appearance inspection should be strengthened, and any abnormality should be handled in time.

4. Completion acceptance 4. 1 The construction unit of lightning protection project must carry out the construction seriously according to the design requirements, and the project construction management department should have a special person responsible for supervision. Concealed works should be accepted with the project, and important parts should be photographed and recorded. 4.2 Design data and construction records shall be properly filed by the corresponding lightning protection department for future reference, and the communication station shall be equipped with lightning protection design data of this station. 4.3 After the completion of the project, the communication engineering construction management department will organize the acceptance, and the communication operation department and the lightning protection engineer will participate. 4.4 If the lightning protection system of the communication station does not meet the design requirements or the data of the lightning protection system is incomplete, it will not be accepted.

5 lightning damage analysis and statistics 5. 1 lightning damage analysis 5. 1. 1 investigation and analysis mainly include: a. whether there are traces of breakdown and flashover in each electrical insulation part, whether there is burning smell, damaged parts of equipment components and changes of equipment electrical parameters; B. Damage of various lightning protection elements and change of parameters; C. If a lightning measuring device is installed, the measurement data shall be recorded and the lightning current amplitude shall be calculated; D. Understand the situation near the lightning accident site, and analyze the characteristics of nearby geology, topography and surrounding environment as well as the meteorological conditions at that time; E. Keep the parts damaged by lightning strike, take photos or videos of the site when necessary, and make various records. 5. 1.2 According to the above investigation, organize relevant experts to make analysis, and write investigation and analysis report and improvement measures. 5.2 Statistics of lightning damage 5.2. 1 In order to do a good job in lightning protection of communication stations, it is necessary to understand the law, intensity and probability of lightning strike, master the damage of equipment and the ways of lightning intrusion, and accumulate necessary information. 5.2.2 Each unit shall establish the archives of lightning activities in the local area according to the specific conditions, and make statistics on lightning disasters. Statistics can be determined by yourself. 5.2.3 After the communication station is damaged by lightning, the preliminary situation shall be reported to the competent department of communication and lightning protection step by step in time. The competent department of communication and lightning protection of each network bureau and provincial bureau shall summarize and report the statistics of lightning damage of power system communication stations (see table 1) to Guodian Communication Center before the end of June each year. Table 1 Statistical Table of Lightning Damage of Power System Communication Station Fill in the name of the unit line of the person in charge of lightning protection. Lightning protection engineer site terrain equipment lightning damage activation time station name altitude m equipment standard mode/times lightning damage The main reasons and improvement measures are as follows.

Appendix A Lightning Protection Technical Standards and Measures (Supplementary Part) A 1 Grounding and voltage sharing A 1. 1 The smaller the grounding resistance, the lower the overvoltage value. Therefore, the grounding resistance should be reduced as much as possible on the premise of economy and rationality. See Table A 1 for its requirements. Table A 1 grounding resistance requires the name of grounding grid. The grounding resistance is generally high soil resistivity 1 dispatching and communication complex building.

A 1.2 the communication stations in the dispatching communication complex should share a grounding network with the power plants and lightning protection devices in the same building. The main reinforcement of the building can be used for the down lead of the building and the communication room. The upper and lower connection points of the main reinforcement itself should be welded by overlapping, and its upper end should be welded with the lightning protection device on the roof, the lower end with the grounding grid, and the middle with the equalizing grid or annular grounding bus of each floor to form an electrically connected cage grounding system. As shown in Figure A. A 1.3, at least two grounding grids of communication stations located in power plants and substations (switches) should be used. A 1.4 Grounding body A 1.4. 1 Grounding body is generally made of galvanized steel, and its specifications should be determined according to the maximum fault current, which should generally be not less than the following values. Angle steel: 50 mm× 50 mm× 5 mm; Flat steel: 40mm×4mm；; Round steel diameter: 8 mm; Thickness of steel pipe: 3.5 mm A 1.4.2 The grounding body shall be buried not less than 0.7m in cold areas, and it shall be buried below the frozen soil. In high water level areas, it is best to reach the known water level to utilize the water source in the saturated area, and all the connection points between grounding bodies shall be lap welded. Welding points (except those poured in concrete) shall be treated with anti-corrosion. A 1.4.3 For areas with high soil resistivity, when the grounding resistance value in common use is difficult to meet the requirements, the grounding body can be extended outward to improve the conductivity of the soil, and the electrode is buried deeply, and grounding protection measures against direct lightning can be taken. A 1.5 communication room building should have grounding protection measures. The roof should be paved with a closed balance net (belt) and connected to the grounding net. The distance from any point on the roof plane to the balance zone should not be greater than 5m. A 1.6 in the communication room, an annular grounding bus (hereinafter referred to as the annular bus) should be laid around the room. Generally, copper bars or galvanized flat steel with a cross section of not less than 90mm2 should not be used for annular grounding buses. Outside the machine room, a closed annular grounding grid should be laid around the building of the machine room, and at least four symmetrically arranged connecting wires (or main bars) should be connected between the annular grounding bus of the machine room and the grounding grid and the closed pressure equalizing belt on the roof. The distance between adjacent connecting lines shall not exceed 18m. A 1.7 metal sheaths of various cables in the machine room, metal shells and frames of equipment, uncharged metal parts such as air inlet pipes and water pipes, metal structures of buildings such as doors and windows, protective grounding and working grounding, etc. , should be connected to the ring grounding bus in the shortest distance. Bolted parts can be bonded with silver-containing epoxy resin conductive adhesive A 1.8. Multi-stranded copper wire should be used for protective grounding wire of all kinds of equipment, and its section should be determined according to the maximum fault current. Generally, the cross-sectional area of the grounding wire of the conductor shielding layer should be 25 ~ 95mm2, which should be twice the cross-sectional area of the shielding layer. The connection of grounding wire should ensure good electrical contact, and the connection point should be treated with anti-corrosion. A 1.9 before the metal pipeline is introduced indoors, it should be buried directly above 10m, and the buried depth should be more than 0.6m If it cannot be buried, it should be grounded evenly at least twice along the outdoor length of the metal pipeline, and the grounding resistance should be less than 10? ; In areas with high soil resistivity, the grounding resistance should not be greater than 30? ; , but the number of grounding points should be increased appropriately. A 1. 10 The upper and lower ends of the coaxial metal sheath on the microwave tower should be connected to the tower nearby respectively, and then connected to the grounding body again at the entrance of the machine room; When the feeder is long, a connection point with the tower should be added in the middle, and both ends of the outdoor feeder bridge should be connected to the grounding grid, as shown in Figure A2. A 1. 1 1 The power cord of the beacon light on the microwave tower should be inserted into the metal tube with metal sheathed cable or lead wire. The electrical connection between metal pipes should be good (continuous shielding). The metal sheath or metal tube should be connected with the metal structure of the tower at least at the upper and lower ends. Before entering the computer room, the horizontal buried depth should be greater than 10m, and the buried depth should be greater than 0.6m, as shown in Figure A2. A 1. 12 The empty cable introduced into the machine room should be grounded on the distribution frame to prevent the introduced lightning from hitting back at the end of the open wire. The grounding grid of A 1. 13 microwave tower shall be made into a closed annular grounding grid around the tower foundation, and the grounding grid of the tower and the grounding grid of the microwave room shall be connected with at least two galvanized flat steels with specifications not less than 40mm×4mm, as shown in Figure A2. A 1. 14 The metal supports in the cable trench and shaft shall be grounded at least at two points, and the spacing between the grounding points shall not be more than 30m.

A 2 Shielding A2. 1 In order to reduce the electromagnetic interference caused by external lightning, the building steel bars and metal floor frames of the communication room and dispatching communication complex should be welded to each other to form an equipotential faraday cage. If the shielding requirements for the equipment group are high, a metal shielding net should be laid on six sides of the room, and the shielding net should be connected to the annular grounding bus in the room at multiple points. A2.2 After the overhead power lines are guided by the terminal poles in the station, they should be replaced with shielded cables. Before entering the room, the buried depth should be greater than 10m, the buried depth should be greater than 0.6m, and both ends of the shielding layer should be grounded; Unshielded cables should be buried horizontally above 10mm through galvanized iron pipes, and both ends of the iron pipes should be grounded, as shown in Figure A2. A2.3 Outdoor communication cables shall be shielded cables, and both ends of the shielding layer shall be grounded; For cables with both armored belt and shielding layer, the armored belt and shielding layer should be grounded simultaneously in the machine room. At the other end, only the shielding layer is grounded, and the cable can only enter the room if it is buried horizontally above 10m. Buried depth should be greater than 0.6m, unshielded cables should be laid in galvanized iron pipes, buried horizontally above 10mm, and both ends of the iron pipes should be grounded. A2.4 Power cables (wires) and communication cables (wires) in the machine room should be shielded cables or laid in shielded pipes, and both ends of the shielding layer or metal pipe must be grounded nearby.

A3 Restrict A3. 1 Communication cables must be connected to the security distribution frame (box) before entering the computer room. The distribution frame shall be equipped with limiting devices to suppress the transverse and longitudinal overvoltage of cable pairs. A3.2 Limiter of distribution frame mainly includes varistor, gas discharge tube, fuse, hot wire coil, etc. For microelectronic devices, piezoresistors should be the first choice. A3.3 The metal part of the terminal rod body of the high-voltage overhead distribution line shall be grounded. If it is far away from the main grounding grid, it can be grounded independently, and the grounding resistance should not exceed 30? ; . The lightning rod should be installed on the pole. A3.4 The lightning arrester shall be installed on the high and low voltage sides of the distribution transformer near the transformer. When the transformer is indoors, the lightning arrester on the high voltage side should generally be installed outdoors, and the distance from the main body should not exceed 10m. Zinc oxide lightning arresters (boxes) should also be installed on three opposite sides of the distribution board or rectifier in the machine room. A3.5 The "positive pole" of DC power supply should be grounded at the power supply equipment side and communication equipment side, and the "negative pole" should be connected with three varistors at the power supply room side and communication room side. A3.6 All kinds of lightning arresters should shorten the lead wire as much as possible, and be directly installed at the protected electrical "line" point. All kinds of lightning arresters must meet the standard requirements and can only be used after passing the inspection by special instruments.

A4 Isolation A4. 1 Isolation measures should be taken for communication lines between different grounding grids to prevent high and low potential counterattack, such as photoelectric isolation and transformer isolation. A4.2 In the power dispatching and communication complex building, it is necessary to set up special equipment with grounding grid, which can be connected with the main grounding grid of the building through the breakdown fuse or discharger to ensure normal isolation. Equilibrium potential during lightning strike. A4.3 The distance between microwave tower and antenna and surrounding buildings should meet the requirements of avoiding flashover of multiple buildings, and the distance should be more than 5m. A4.4 Except the necessary communication equipment, other equipment that may cause lightning strike threat, such as cables, wires, TV antennas and feeders, shall not be erected or hung on the microwave tower.

A5 Other clauses of lightning protection technical standards and measures for other communication stations shall conform to the relevant parts of SDJ-79 Technical Specification for Grounding Design of Power Equipment and SD-79 Technical Specification for Overvoltage Protection Design of Power Equipment.