According to the mechanism of lightning-struck disconnection of insulated wires, generally speaking, the corresponding preventive measures mainly include two ways: “draining” and “blocking”.

The so-called “grooming” is to partially bare the insulated wire near the insulator, so that the power frequency arc root is transferred or fixed on a special fitting to burn, so as to protect the wire from burns.

For example, Finland uses flashover protection clamps to strip the insulation at the junction of the insulator and the wire; Sweden and the United States strip a section of the insulation on the insulated wires on both sides of the insulator and install an arc-proof clamp; Japan uses the wire insulation layer at the insulator Stripping, using discharge clamp insulators.

The “draining” method is simple in operation and low in investment, but it is partially exposed and has sealing and insulation defects. In addition, the wire clamp device often has the problem of poor seismic performance, and failures often occur when the line is fluttering. The so-called “blocking” is to prevent the power frequency freewheeling arc after lightning flashover. For example, Japan has adopted a large number of overvoltage protectors, that is, metal oxide arresters with series ring external gaps.

Economically developed countries have used overhead insulated conductors for transmission and distribution for a long time and accumulated a lot of operating experience. In order to reduce the ever-increasing rate of lightning strikes and disconnection accidents, many preventive measures and methods have been adopted, as follows:

1) Overhead lightning protection line

In open areas, erecting overhead lightning protection lines on the same pole to deal with the induced overvoltage of the overhead insulated lines for power distribution is a traditional method with a large investment. However, due to the low insulation level of the power distribution line design, lightning strikes on the overhead lightning protection line are very likely to cause flashover in the counterattack, which will still cause the power frequency continuous current to fuse the insulated wires. Therefore, this method is rarely used abroad.

2) Zinc oxide arrester

In recent years, people have made use of the non-linear resistance characteristics of zinc oxide arresters and the characteristics of quickly blocking power frequency freewheeling. They are widely used in lines to limit lightning overvoltage, but their protection range is small, and the reason that the insulation layer must be broken may cause Water in the insulated wire core caused electrochemical corrosion and disconxxxxx cccccccccccccccccccccccccnection at the sag of the zinc o   xide arrester wire. At the same time, it may cause aging of the zinc oxide  operation and maintenance.

This law has a very good protective effect, and it has been applied in Japan, the United States, Canada, etc. through huge investments.

3) Clamping insulator

Tokyo Electric Power Company of Japan uses discharge clamp insulators to prevent the insulated wires from breaking due to lightning. That is, peel off the insulating layer at the fixed place of the insulated wire, install a specially designed metal clamp, and set the arc discharge gap. When the lightning flashover causes the power frequency freewheeling, the power frequency freewheeling arcs on the metal clamp until the line trips to extinguish the power frequency freewheeling, so as to avoid burning the insulators and fuse the insulated wires. However, the investment cost of replacing the insulated wire is relatively high and the insulation layer must be broken, which may cause water in the insulated wire core, resulting in electrochemical corrosion at the sag of the wire and disconnection.

4) Growth flashover path

By increasing the flashover path and reducing the power frequency arcing rate, it is another idea to prevent lightning strikes and disconnection of overhead insulated lines. The Russian State Power Company first proposed a long flashover gap protection method. A U-shaped insulated flashover path is installed on the cross arm, so that the impulse discharge voltage between the U-shaped head and the insulated wire is lower than that of the insulator. When lightning overvoltage occurs, the gap precedes the insulator breakdown flashover and develops along the insulation flashover path. The design of the insulation path is long enough to prevent the power frequency freewheeling from creating arcs and cut off the power frequency freewheeling. However, the problem of how to maintain the gap and how to maintain a standard distance with other lines on the same pole has not been resolved.

5) Improve line insulation level

The porcelain insulators in the power distribution lines are replaced with silicone rubber insulated cross arms, and the insulation level of the lines is improved throughout the line. The power frequency freewheeling caused by lightning cannot be built because of the large creeping distance. However, the investment is relatively high and the renovation project is relatively large.

6) Lightning overvoltage protector for insulated lines

Some lightning-prone countries such as Japan, Australia, the United States and Europe have widely promoted the application of line overvoltage protectors on overhead insulated lines in recent years.

The device uses the outer gap to form an outer discharge gap for the zinc oxide current limiting element. When a lightning overvoltage occurs on the line, the outer gap discharges first, and the lightning current is released through the zinc oxide current limiting element, while the power frequency freewheeling is caused by the zinc oxide The current-limiting element is cut off to prevent the occurrence of lightning-stroke disconnection of overhead insulated lines.

This method has been popularized and applied in many countries for four years, and it has effectively prevented the occurrence of lightning-stroke disconnection accidents. It is generally welcomed by many countries and is gradually replacing the above-mentioned preventive measures.

In the above technical solutions, the gapless lightning arrester and the insulated line overvoltage protector have relatively good application effects and are widely used.