How is the lightning arrester protection of the transformer carried out?

The lightning arrester is the most crucial basic component for protecting power generation equipment and transmission and transformation equipment. It also forms the foundation for determining the insulation level of high-voltage electrical equipment. Installed in front of the transformer, the arrester mainly consists of a spark gap and a non-linear resistor (valve plate). When the overvoltage generated by lightning attacks the transformer, it first passes through the arrester. At this point, the spark gap of the arrester discharges, thereby limiting the overvoltage on the insulation of the transformer. During the discharge process, the non-linear resistor with good volt-ampere characteristics limits the residual voltage (the voltage drop caused by the discharge current passing through the non-linear resistor) on the arrester to a value that is not dangerous for the transformer. The lower the residual voltage, the lower the insulation level of the transformer.

After the gap is broken, the power frequency voltage acting on the arrester generates a power frequency current, namely accompanying current. Due to the non-linear resistance of the valve plate, it limits the accompanying current to a small value, generally below 50A, and is cut off when it first passes through zero. After the overvoltage has passed, relying on the action of the valve plate and the gap, the valve-type arrester can automatically cut off the power frequency continuous flow, isolating the working voltage of the transmission system from the ground. This restores the arrester to its normal state before the lightning strike. However, current valve-type arresters still cannot fully protect against operational overvoltages.

The magnetic blow valve-type arrester uses a magnetic blow current-limiting gap, ensuring the stability of the arrester's discharge voltage. At the same time, this type of gap itself has the characteristic of elongating the arc, creating a considerable arc voltage drop, which increases the reliability of the arrester's arc extinction. The valve plate is made of high-temperature materials, so it has a large current-carrying capacity, and the residual voltage during the passage of the transient current is low. This not only protects the transformer from the invasion of lightning overvoltages but also has the ability to limit certain types of operational overvoltages.

Zinc oxide arresters have no gaps, resulting in even lower residual voltage. They have been applied in the protection of ultra-high voltage transformers.

LuShan, est. 1975, is a Chinese professional manufacturer specializing in power transformers and reactors for 49 years. Leading products are single-phase transformer, three-phase transformers, DC inductors, AC reactors, filtering reactor, expoxy resin high-voltage transformer and intermediate, high-frequency products. Our transformers and reactors are widely used in 10 application areas: rapid transit, construction machinery, renewable energy, intelligent manufacturing, medical equipment, coal mine explosion prevention , excitation system, vacuum sintering, central air conditioning.

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