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Most of the accidents in the power grid are based on the faults of the transmission lines, and the faults of the transmission lines are the most striking ones due to lightning strikes, especially in the mountains. Line faults are mostly caused by lightning strikes. The author summarizes the lightning tripping situation and lightning protection work of transmission lines and puts forward suggestions for improvement to improve the lightning protection capabilities of transmission lines in order to promote the stable operation of the power grid.
1. Two main manifestations of line lightning stroke tripping
One is direct lightning, which refers to the rapid discharge between charged clouds and a certain point on the earth. The direct lightning strike is huge, lightning voltage can reach tens of thousands of volts to millions of volts, instantaneous current can reach hundreds of thousands of amperes, and objects will be burned by high temperature or even melted in the thunder and lightning path. Thunder strikes lightning strikes on the top of the tower and near the top of the tower, generally causing flashover of one or more phases of the tower of the tower. Zinc oxide surge arresters can be installed to prevent lightning.
The other is to circumvent thunder and lightning. It is to bypass the lightning conductor and hit the wire. The thunder and dodge occurs in the large span and the open area around the line. Generally caused by the flashing of the side-phase porcelain string, the side is corresponding to the side facing the thundercloud. Sometimes, the lightning current is larger. After the lightning bypasses the wire, the lightning current is transmitted along the two sides of the wire, which also causes the adjacent The tower flashes in parallel with the porcelain string, and when large lightning currents are circumvented on the conductors of the side tower, the tower string flashes. At the same time, due to the large lightning current, the tower top is caused when the pole tower enters the ground. The high potential can also cause the flashback of other phases of the porcelain bottle caused by counterattack. A 10KV zinc oxide surge arrester can be installed for lightning protection.
2. Technical precautions to improve and reduce the lightning strike rate
2.1 Carry out analysis of lightning parameters
Combining with the implementation of the project of the Intelligent Transmission Inspection System for Power Transmission, the GPS satellite positioning of the transmission line towers of 110 kV and above is realized, and the data is input into the lightning positioning system. In the future, when there is a lightning day in the area, the situation of lightning activity near the transmission line can be inquired in time, and the parameters of the lightning activity can be analyzed to determine the probability that the line may be struck by lightning, and to classify the level of lightning damage suffered by the transmission line, and take appropriate measures accordingly. Lightning protection measures.
2.2 erection of lightning conductors
This is the basic measure for lightning protection of high-voltage lines. Its main role is to prevent direct lightning strikes on conductors and to over-voltage the insulation. After the lightning arrester is installed, the lightning current enters the ground along the lightning conductor and leads down the ground to ensure the safe power supply of the line. According to the grounding resistance of the grounding conductor, different potentials are formed at the top of the tower. At the same time, when the lightning wave propagates in the lightning conductor, it will couple with the conductors of the circuit and induce a traveling wave, but this line involves pole potentials. The over-voltage amplitude applied to the line insulation is much smaller than the over-voltage amplitude that occurs when the lightning wave strikes the wire in the file. Lines with voltage ratings of 110kV and above should generally be equipped with lightning conductors all over the line. Zinc oxide surge arresters can be installed for lightning protection.
2.3 Use of Zinc Oxide Arrester
In Dorayan, the use of suitable zinc oxide surge arresters is very effective in preventing lightning accidents. Because the zinc oxide arrester action limits the potential difference between the two ends of the insulator, it can effectively prevent counterattack accidents. On-site operating experience shows. Several high-voltage surge arresters are installed on the lines of lightning-prone areas. It is very effective in preventing lightning strikes and tripping accidents. In order to limit the intrusion of lightning waves along the line into power plants or substations. A further line of arresters can be installed in the terminal tower of the line. According to relevant information. It is not appropriate to install the zinc oxide surge arrester on the grounding of the tower. Because the zinc oxide arrester is like other lightning protection facilities. It is also through the grounding device to discharge the lightning current to the earth. Therefore, the grounding resistance of the tower and the down conductor should be strictly required because the zinc oxide arrester installed on the line is inconvenient to maintain. So try to use maintenance-free zinc oxide surge arresters.