Pole-mounted vacuum circuit breakers should be installed with lightning arresters, lightning arrester manufacturers
The main reason why column-mounted vacuum circuit breakers are frequently struck by lightning is that the circuit breakers are not equipped with lightning arresters.
1. Lightning strike situation
In recent years, accidents of pole-mounted circuit breakers burning due to lightning strikes have occurred frequently and are showing a growing trend. Especially after the transformation of urban and rural power grids, the quality of the power grid has been greatly improved. Accidents of line short circuits or single-phase grounding caused by lightning strikes have dropped significantly, while accidents of pole-mounted circuit breakers being damaged by lightning strikes have continued unabated.
2. Analysis of accident causes, cold shrink cable terminal
The main reason why column-mounted vacuum circuit breakers are frequently struck by lightning is that the circuit breakers are not equipped with lightning arresters. The use of pole-mounted circuit breakers has a long history. At that time, oil circuit breakers were still used. This device was never equipped with a lightning arrester. In fact, there were very few accidents of lightning striking the circuit breaker. Later, after the switch to vacuum circuit breakers, there was no obvious upward trend in lightning accidents. However, two units have been damaged by lightning strikes 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 the pin insulators on all main lines with rod insulators, thereby improving the overall lightning resistance level of the lines, but the weak links of the overall line have been transferred from the insulators to the pole circuit breakers.
In the past, because the breakdown voltage of pin insulators was much smaller than the breakdown voltage of oil circuit breakers, single-phase grounding often occurred due to pin insulator crushing during thunderstorm seasons, but lightning strikes to circuit breakers rarely occurred. With the transformation of lines, all insulators on the main lines have been replaced with rod insulators, and the voltage withstand level of the lines has been greatly improved. The vacuum bubble of the pole-mounted vacuum circuit breaker is placed in an iron shell box, and the external insulation is air, so the withstand voltage level is relatively low. Although its withstand voltage level reaches the specified 42kV/min test requirement, it is far from the withstand voltage level of rod insulators. Moreover, circuit breakers are generally installed on main lines, which are usually along the main road or in open fields, and the poles are higher than branch lines. Therefore, main lines are more susceptible to lightning strikes than branch lines, thus damaging the pole-mounted circuit breakers.
3.Solution
The most direct way to protect the pole-mounted vacuum circuit breaker from lightning strikes is to install a lightning arrester. That is, the lightning 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 open, disconnecting one side of the circuit breaker from the line, while the other side connected to the line is still within the protection range of the lightning arrester. In fact, circuit breakers installed by other power supply bureaus using the above method rarely cause lightning strikes.
Because after a line is struck by lightning, the lightning wave must find a weak point as an outlet. Therefore, after replacing the pin insulator with a rod insulator, in order to prevent the lightning wave from damaging various power facilities, such as knife switches, fuses, suspension insulators and the above-mentioned pole circuit breakers, it is advisable to install a lightning arrester on the line so that the residual voltage of the lightning strike within the protection range of the arrester is less than the withstand voltage level of the electrical equipment. But as a result, a large number of lightning arresters will be added to the lines. The approach adopted by our Bureau is to install the lightning arresters on the upper pile heads of drop-out fuses for all outdoor installed transformers, so that they can be used as both distribution transformer arresters and line arresters. Facts have proved that this installation method has the same protective effect on the transformer as the lightning arrester installed on the lower pile head of the drop-out fuse, and lightning strike distribution transformer accidents rarely occur.
Yichang Hengyuan Technology Co., Ltd. specializes in the production of European-style cable joints, plug-and-pull heads, cable branch boxes, American-style elbow joints, high-voltage vacuum circuit breakers, high-voltage load switches, arresters, zinc oxide arresters, tank arresters, over-voltage protectors, counters, monitors, heat-shrinkable cable accessories, Manufacturer of cold shrink cable accessories, T-heads, wall bushings, European cable accessories, American cable joints, transformer neutral point protection devices, fuses, isolating switches, PT cable heads, elbow cable joints, 10kV outdoor terminals, switch cabinets, cable intermediate joints, cable accessories and other products
