With the rapid development of distribution networks, users are also increasing the quality of power supply. Under the balance between safety and economy, there is a need for higher reliability of power supply. The wiring of the distribution network is relatively complicated, and it is necessary to ensure the flexibility in scheduling, the continuity of power supply in operation, and the economy. This requires the personnel engaged in the operation and maintenance of distribution lines to be familiar with the structure of the line of management, accurately determine the nature and scope of the accident based on the phenomenon of failure, and be able to take reasonable measures to dispose of it in a timely manner to ensure continuous supply of quality and quantity to meet the needs of users. Electricity demand.
A 10kV overhead power distribution line is often subject to lightning strikes, and preventive measures are discussed in order to improve the safe operation of the 10KV distribution network. At present, insulated conductors are widely used in 10KV overhead distribution lines. It can be said that the insulation of overhead wires in distribution networks is a mature technology.
However, some new problems have also arisen in the application of insulated wires. Among them, the most prominent problem is that when a lightning strike occurs, it is prone to breakage accidents. Lightning strike accidents are one of the most serious problems in the application of insulated conductors. This has caused our extensive attention, and we have actively conducted peer-to-peer experimental research and found many effective preventive measures.
First, the lightning breakage and tripping mechanism
1. Rules of arc discharge (1) Distribution network lightning overvoltage flashover, that is, large current discharge at atmospheric pressure or above atmospheric pressure, is an arc discharge form.
(2) When the lightning overvoltage flashover occurs, the instantaneous arc current is large but the time is short.
(3) When the lightning overvoltage flashover, especially in the two-phase or three-phase (not necessarily on the same pole) flashover to form a metal short-circuit channel, causing thousands of amps frequency, freewheeling, arc energy Will increase suddenly.
2. Overhead insulated wire breakage When a lightning strike overhead insulated wire produces a huge lightning overvoltage, when it exceeds the withstand voltage level of the wire insulation layer (usually greater than 139KV) will find the weakest point of the electric field along the wire to penetrate the wire insulation layer (usually within 30 centimeters of both ends of the insulator) to form a breakdown point of the size of the pinhole, and then the surface of the insulator discharges to form a flashover, and finally the metal arc short circuit is formed after the frequency-frequency arc develops to the metal of the insulator root, and the power frequency arc Fix the fuse after burning it.
3. Low overhead wire breakage rate but frequent tripping accidents When lightning strikes overhead conductors generate huge lightning overvoltages, it will find along the conductor the weakest point of the electric field along the surface of the insulator discharge flashover, and finally the power frequency arc to the root of the insulator After the metal's development, a metal short-circuit channel was formed, causing a line tripping accident. As the subsequent short-circuit current of the power frequency short-circuit current is moved along the wire away from the power source under the action of the electromagnetic force, the wire is generally not blown.
Second, arc extinguishing method
1. The root of the arc so that the arc extinguishing an elongated arc-extinguishing circuit breaker trip 2. 3. overvoltage <br> <br> three energy release, and to prevent breakage lightning trip accident ideas
1. Improve the insulation level of the line or avoid lightning overvoltage. Such as: local reinforced insulation, overhead lightning protection line 2. The arc burning fuse wire extended to exceed the time of the circuit breaker tripping, arc extinguishing through the tripping of the circuit breaker. Such as: discharge insulators, protection gaps, lightning fittings, etc. 3. Make the arc extinguish momentarily before the fuse is blown. Such as: arrester, line over-voltage protection, etc.
A 10kV overhead power distribution line is often subject to lightning strikes, and preventive measures are discussed in order to improve the safe operation of the 10KV distribution network. At present, insulated conductors are widely used in 10KV overhead distribution lines. It can be said that the insulation of overhead wires in distribution networks is a mature technology.
However, some new problems have also arisen in the application of insulated wires. Among them, the most prominent problem is that when a lightning strike occurs, it is prone to breakage accidents. Lightning strike accidents are one of the most serious problems in the application of insulated conductors. This has caused our extensive attention, and we have actively conducted peer-to-peer experimental research and found many effective preventive measures.
First, the lightning breakage and tripping mechanism
1. Rules of arc discharge (1) Distribution network lightning overvoltage flashover, that is, large current discharge at atmospheric pressure or above atmospheric pressure, is an arc discharge form.
(2) When the lightning overvoltage flashover occurs, the instantaneous arc current is large but the time is short.
(3) When the lightning overvoltage flashover, especially in the two-phase or three-phase (not necessarily on the same pole) flashover to form a metal short-circuit channel, causing thousands of amps frequency, freewheeling, arc energy Will increase suddenly.
2. Overhead insulated wire breakage When a lightning strike overhead insulated wire produces a huge lightning overvoltage, when it exceeds the withstand voltage level of the wire insulation layer (usually greater than 139KV) will find the weakest point of the electric field along the wire to penetrate the wire insulation layer (usually within 30 centimeters of both ends of the insulator) to form a breakdown point of the size of the pinhole, and then the surface of the insulator discharges to form a flashover, and finally the metal arc short circuit is formed after the frequency-frequency arc develops to the metal of the insulator root, and the power frequency arc Fix the fuse after burning it.
3. Low overhead wire breakage rate but frequent tripping accidents When lightning strikes overhead conductors generate huge lightning overvoltages, it will find along the conductor the weakest point of the electric field along the surface of the insulator discharge flashover, and finally the power frequency arc to the root of the insulator After the metal's development, a metal short-circuit channel was formed, causing a line tripping accident. As the subsequent short-circuit current of the power frequency short-circuit current is moved along the wire away from the power source under the action of the electromagnetic force, the wire is generally not blown.
Second, arc extinguishing method
1. The root of the arc so that the arc extinguishing an elongated arc-extinguishing circuit breaker trip 2. 3. overvoltage <br> <br> three energy release, and to prevent breakage lightning trip accident ideas
1. Improve the insulation level of the line or avoid lightning overvoltage. Such as: local reinforced insulation, overhead lightning protection line 2. The arc burning fuse wire extended to exceed the time of the circuit breaker tripping, arc extinguishing through the tripping of the circuit breaker. Such as: discharge insulators, protection gaps, lightning fittings, etc. 3. Make the arc extinguish momentarily before the fuse is blown. Such as: arrester, line over-voltage protection, etc.
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