How to Lightning Protection of Outdoor Transformer

In power system, outdoor transformer is the key equipment in transmission and distribution system, and its safety and stability directly affect the normal work of the whole power grid. Because outdoor transformers are usually installed in the open air, they are easily attacked by lightning, so it is very important to take effective lightning protection measures to ensure the safe operation of transformers.

First, the harm of lightning to outdoor transformers

Lightning is a natural phenomenon with high voltage and high current. When lightning strikes a transformer or falls near it, it will produce extremely high overvoltage, which may cause insulation breakdown of the transformer, winding damage, and even cause serious accidents such as fire or explosion. In addition, when lightning current passes through the grounding system, it may also cause the ground potential to rise and cause counterattack damage to the secondary equipment.

Second, the common lightning protection measures

1. Lightning arrester protection
Lightning arrester is the most important lightning protection device for outdoor transformers. Usually, a set of zinc oxide arresters are installed on the high voltage side and the low voltage side of the transformer to limit the overvoltage caused by lightning wave intrusion and introduce lightning current into the earth, thus protecting the transformer insulation system. The lightning arrester should be installed as close as possible to the transformer and ensure a good grounding connection.

2. Set lightning rod or overhead lightning wire.
In some areas with frequent lightning activities, independent lightning rods or overhead lightning wires can be set near the transformer to form a protection area to guide lightning current into the ground safely and reduce the possibility of direct lightning strike.

3. Good grounding system
The quality of grounding system directly affects the lightning protection effect. Transformer shell, lightning arrester and neutral point should be reliably grounded, and the grounding resistance should be less than 4Ω. In areas with high soil resistivity, grounding resistance can be reduced by adding grounding electrodes and using resistance reducer.

4. Strengthen line lightning protection
In addition to protecting the transformer body, lightning protection measures should also be taken for the transmission lines connecting the transformer, such as erecting overhead ground wires and installing line lightning arresters to prevent lightning waves from invading the substation along the line.

Third, the daily maintenance and management

After the installation of lightning protection facilities, it is necessary to strengthen daily maintenance and regular inspection. For example, regularly check whether the working state of lightning arrester and grounding resistance meet the requirements; Before the thunderstorm season, the lightning protection device should be inspected comprehensively to ensure that it is in good condition; At the same time, a lightning accident recording and analysis mechanism should be established to find and deal with hidden dangers in time.

IV. Conclusion

In a word, lightning protection of outdoor transformer is a systematic project, which needs comprehensive consideration from equipment selection, structural layout, grounding system design to daily operation and maintenance. Only through scientific and reasonable design and management can the lightning protection ability of transformer be effectively improved and the safe and stable operation of power system be guaranteed. In areas with frequent lightning, more attention should be paid to lightning protection to ensure the safety of power facilities during the thunderstorm season.