The vacuum circuit breaker on the pole should be installed with a lightning arrester.

The main reason for the frequent lightning strikes of the vacuum circuit breaker on the pole is that the circuit breaker is not installed with a lightning arrester.

1　Lightning strike situation

In recent years, lightning strikes have caused frequent incidents of circuit breakers burning on poles, and they are increasing. Especially after the transformation of urban and rural power grids, the quality of the power grid has been greatly improved, and the incidents of short circuit or single-phase grounding caused by lightning are obvious. However, incidents of lightning damage to the on-pillar circuit breaker have continued unabated.

2　Analysis of the cause of the accident, cold shrinkable cable terminal

The main reason for the frequent lightning strikes of the vacuum circuit breaker on the pole is that the circuit breaker is not installed with a lightning arrester. There has been a long history of using pole-mounted circuit breakers. At that time, oil circuit breakers were used. The device has never been equipped with a lightning arrester. In fact, there are very few incidents of lightning strikes to the circuit breaker. After it was changed to a vacuum circuit breaker, there was no obvious upward trend in lightning accidents. However, two of them have been burned by lightning recently. The reason is that in recent years, our bureau has carried out large-scale construction and transformation of the power grid, maintained the lines, and replaced all the pin insulators on the main trunk lines with rod insulators, thereby improving the overall lightning resistance level of the line. However, the overall weak link of the circuit is transferred from the insulator to the post circuit breaker.

In the past, because the breakdown voltage of pin insulators was much smaller than that of oil circuit breakers, single-phase grounding was often caused by pin insulators breaking during thunderstorm seasons, but lightning breaker accidents were rare. With the transformation of the line, all the insulators on the main line were replaced with rod insulators, and the withstand voltage level of the line was greatly improved. The vacuum bubble of the vacuum circuit breaker on the column is placed in an iron box, and the outer insulation is air, so the relative ground withstand voltage level is relatively low. Although its withstand voltage level reaches the specified 42kV/min test requirement, it is different from the rod The withstand voltage level of the type insulator is quite different. Moreover, circuit breakers are generally installed on the main line, and the main line is usually on the side of the main road or in the open field, and the pole is higher than the branch line, so the main line is more susceptible to lightning strikes than the branch line, so that the pole-mounted circuit breaker Damaged.

3　Solution

The most direct way to prevent the vacuum circuit breaker on the pole from being struck by lightning is to install a lightning arrester. That is, the arrester is installed on the side of the circuit breaker directly connected to the line. The advantage of this installation method is that when the circuit breaker is opened, the contacts are opened, so that one side of the circuit breaker is disconnected from the circuit, and the other side of the circuit connection part is still in the protection range of the arrester. In fact, the circuit breakers installed by other power supply bureaus using the above method rarely have lightning accidents.

After the line is struck by lightning, the lightning wave must find a weak point as a way out. Therefore, after replacing pin insulators with rod insulators, in order to avoid lightning strikes from damaging various power facilities, such as: knife switch, fuse, suspension Insulators and the above-mentioned pole circuit breakers, etc., it is advisable to install a lightning arrester on the line so that the lightning residual voltage within the protection range of the arrester is less than the withstand voltage level of the power equipment. But in this way, a large number of lightning arresters will be added to the line. The method adopted by our bureau is to install the lightning arrester on the upper pile head of the drop-out fuse for all transformers installed outdoors, so that it can be used as a distribution transformer lightning arrester as well as a line lightning arrester. Facts have proved that this installation method has the same protective effect on the transformer as the lightning arrester is installed on the lower pile head of the drop-out fuse, and lightning strikes and distribution transformer accidents are rare.

Yichang Hengyuan Technology Co., Ltd. is a professional manufacturer of European-style cable connectors, plug connectors, cable branch boxes, American elbow connectors, high-voltage vacuum circuit breakers, high-voltage load switches, lightning arresters, zinc oxide arresters, tank arresters, overvoltage protectors, Counters, monitors, heat-shrinkable cable accessories, cold-shrinkable cable accessories, T-shaped heads, wall bushings, European cable accessories, American cable connectors, transformer neutral point protection devices, fuses, isolation switches, PT cable heads, elbows Manufacturers of type cable joints, 10kV outdoor terminals, switch cabinets, cable intermediate joints, cable accessories and other products