To prevent 10kV overhead insulated conductors from lightning strikes and technical measures - News - Global IC Trade Starts Here Free Join

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According to the mechanism of lightning strikes on insulated wires, in general, the corresponding preventive measures mainly include “sparging” and “clogging”. The so-called "grooming" means that the insulated wires near the insulators are partially bare-lined, so that the power frequency arc roots are transferred or fixed on the special fittings to protect the wires from burns. For example, Finland uses a flashover-protected clamp for stripping the insulation between the insulator and the wire; Sweden and the United States strip the insulated conductors on both sides of the insulator with an insulating layer and an anti-arc clamp; the insulation of the conductor at the insulator in Japan Peel off, using a discharge clamp insulator. The “grooming” method is simple in operation and low in investment, but it is partially exposed, and there are sealing and insulation defects. In addition, the wire clamp device often has a problem of poor seismic performance, and often occurs when the line winds and blows. The so-called "blocking" is to prevent the power frequency from being flashed after the lightning strikes. For example, Japan uses a large number of overvoltage protectors, that is, a metal oxide surge arrester with a series ring-shaped outer gap.
Economically developed countries have adopted a long time for transmission and distribution of overhead insulated wires, and accumulated a lot of operational experience. In order to reduce the rising rate of lightning strikes, a number of preventive measures and methods have been adopted, as follows:
(1) Overhead lightning protection line In the open area, an overhead lightning protection line is erected on the same pole to deal with overvoltage induced by the overhead transmission line. This is a traditional method with large investment. However, due to the low insulation level of the distribution circuit design, it is very easy to cause the flashback after the lightning strike of the lightning protection line, and the power frequency will continue to fuse the insulated conductor. Therefore, this method is currently rarely used abroad.
(2) Zinc Oxide Arresters In recent years, people have used the non-linear resistance characteristics of zinc oxide arresters and the characteristics of rapidly blocking power frequency freewheeling, which are widely used in lines to limit lightning overvoltage, but their protection range is small, and insulation must be broken. The reason of the layer may cause the insulated wire core to enter the water, resulting in electrochemical corrosion and corrosion of the zinc oxide arrester wire. At the same time, when the power frequency voltage is applied, the zinc oxide valve piece may be aged, and the operation and maintenance amount is increased.
This method has a very good protective effect. This method has been applied in Japan, the United States, Canada, etc. by investing huge sums of money.
(3) Clamp insulator Japan Tokyo Electric Power Co., Ltd. uses a discharge clamp insulator to prevent the insulated wire from being broken. That is, the insulating layer is peeled off at the fixed position of the insulated wire, a specially designed metal wire clip is added, and an arcing discharge gap is set. When the lightning flashover induces the power frequency freewheeling, the power frequency freewheeling arcs on the metal wire clamp until the line trips to extinguish the power frequency freewheeling, thereby avoiding burning the insulator and blowing the insulated wire. However, the investment cost of replacing the insulated wire is large, and the insulation layer must be broken to cause the insulated wire core to enter the water, which causes the electrode to be electrochemically corroded and broken.
(4) Increasing the flashover path By increasing the flashover path and reducing the rate of construction frequency, it is another way to prevent lightning strikes on overhead insulated lines. The Russian National Power Company first proposed a long flashover gap protection method. A U-shaped insulating flashover path is mounted on the cross arm so that the impact discharge voltage between the U-shaped head and the insulated wire is lower than the insulator discharge voltage. When the lightning overvoltage, the gap breaks down before the insulator breaks down and develops along the insulation flashover path. Designing the insulation path to be long enough can prevent the power frequency from continuing to build the arc and cut off the power frequency freewheeling. However, the problem of how to maintain the gap and how to maintain the standard spacing with other lines on the same pole has not been solved.
(5) Improve the insulation level of the line Replace the porcelain insulator in the distribution line with the silicon rubber insulation cross arm, and improve the insulation level of the line. The power frequency continuous flow caused by lightning is unable to build the arc due to the large creep distance. However, the investment is higher and the renovation project is larger.
(6) Insulated line lightning overvoltage protectors Some countries with multiple lightning damage such as Japan, Australia, the United States and Europe have recently popularized the application of line overvoltage protectors on overhead insulated lines. The device utilizes the outer gap to form an outer discharge gap for the zinc oxide current limiting element. When a lightning overvoltage occurs in the line, the outer gap is first discharged, the lightning current is released by the zinc oxide current limiting element, and the power frequency freewheeling is replaced by zinc oxide. The current limiting component is cut off to prevent the occurrence of lightning strikes on the overhead insulated line. This method has been widely used in many countries for four years to effectively prevent the occurrence of lightning strikes. It has been widely welcomed by many countries and is gradually replacing the above-mentioned preventive measures.
In the above technical solution, the gapless arrester and the insulated line overvoltage protector have relatively good application effects, and are widely used.
The two technical solutions are further discussed below.
 Non-gap type arrester without gap type arrester is used for line lightning protection. The arrester is directly connected with the wire. This is a continuation of the power station type arrester technology. It has the advantages of reliable absorption of impact energy and no discharge delay (the other is with gap). Type: The arrester and the wire are connected through the air gap, and only bear the effect of the power frequency voltage when the lightning current acts, which has the advantages of high reliability, long operating life and the like).
However, since the gapless arrester is subjected to the power frequency voltage for a long time, it is also subjected to the lightning overvoltage and the power frequency freewheel intermittently, and the arrester is easily deteriorated, so the arrester has many faults. Since the arrester is directly connected to the wire, when the arrester fails, it may affect the normal power supply of the line.
绝缘 Insulated Line Lightning Overvoltage Protector Line The current limiting component of the overvoltage protector is connected in parallel with the line insulator. When lightning strikes the tower pole or lightning protection line, the high potential caused by the lightning current causes the line protector to operate in series, reducing the tower arm. The potential difference between the conductor and the conductor ensures that the insulator is no longer flashing, thus avoiding line tripping and power failure. After the series gap action, the residual voltage of the current limiting element body is not only limited to be much lower than the flashover voltage in the insulator, but also can extinguish the power frequency freewheeling after the lightning power voltage system power frequency voltage to ensure normal power supply.
This device has several advantages:
When the line is in normal operation, the overvoltage protector is not subjected to the continuous power frequency working voltage. In the "rest" state, the charge rate of the current limiting element resistor valve can be higher, and the lightning residual voltage can be reduced accordingly;
2 The current limiting component is only in the working state after the series gap action under the lightning overvoltage of a certain amplitude, so the outer insulation level (the insulation jacket creepage distance) can be lower than the gapless arrester.
3 On the normally designed circuit, there is sufficient ability to withstand the overvoltage, and the gap size can be selected to avoid the action of operating the overvoltage, which can greatly reduce the pressure of the current limiting component operating load test.
4 Due to the isolation of the series gap of the stainless steel drain ring, even if the current limiting element resistor is degraded, it will not affect the normal operation of the line.
In fact, relevant information shows that in Japan by January 1999, more than 47,000 lines of overvoltage protectors with different voltage levels were in operation. Obviously, Japan has used a large number of line overvoltage protectors to improve the lightning resistance level of transmission lines, and achieved good operation results.