【Grain Rain】Thunderstorm season has arrived! How to choose transformer arrester?


Release time:

2023-04-20

Guyu means "rain produces hundreds of grains" and is the last solar term in spring. After entering Guyu, precipitation will increase significantly, which also means the arrival of thunderstorm season. For electrical equipment, in addition to moisture protection, lightning protection is also an important protection task.

Guyu means "rain produces hundreds of grains" and is the last solar term in spring. After entering Guyu, precipitation will increase significantly, which also means the arrival of thunderstorm season. For electrical equipment, in addition to moisture protection, lightning protection is also an important protection task.

 

There are two situations when electrical equipment is struck by lightning: one is a direct lightning strike on the equipment, and the other is a lightning wave formed by lightning-induced overvoltage and direct lightning overvoltage of overhead lines that invades the substation along the lines. Both situations will cause serious damage to electrical equipment and cause safety accidents.

(1) Direct lightning overvoltage: Thunderclouds directly hit power equipment, forming lightning current and higher voltage. When lightning current passes through an object, it produces destructive thermal and mechanical effects.

(2) Induced overvoltage: Thunderclouds appear above overhead wires and accumulate a large amount of opposite sex-bound charges due to static electricity. When thunderclouds discharge to the earth, the charges on the lines are released, and the free charges formed flow to both ends of the lines, generating high overvoltage, causing insulation damage to the electrical equipment in the substation and causing accidents.

In order to prevent lightning from damaging the transformer, lightning arrester equipment is used to protect it. A lightning arrester is an electrical device used to protect electrical equipment from overvoltage hazards. Its main features are:

It is in a high resistance state under normal operating voltage (normal state), but when encountering lightning overvoltage (external overvoltage) or operating overvoltage (internal overvoltage), its resistance instantly decreases to a low resistance state, and the conduction discharge is excessive. voltage, thereby protecting electrical equipment.

In the selection and use of lightning arresters, there are the following basic index requirements:

1. Volt-second characteristics: refers to the corresponding relationship between voltage and time. The arrester should have a flat volt-second characteristic curve and reasonably match the volt-second characteristic curve of the protected equipment. In this way, before the protected equipment may break down, the arrester will act to cut off the overvoltage wave, thereby providing reliable protection.

2. Power frequency freewheeling: In order not to cause the circuit breaker to trip, the arrester should have the ability to quickly cut off the power frequency freewheeling on its own and restore the insulation strength, so that the power system can continue to work normally.

3. Instantaneous characteristics: When a lightning strike acts on a transmission line, the overvoltage wave will invade the power plant/substation along the wire. When the insulation of the protected equipment is endangered, the arrester is required to act instantaneously to reflect the instantaneous characteristics.

4. Insulation strength self-recovery ability: that is, the speed of recovery to the original insulation strength.

5. Rated voltage of the arrester: When the power frequency freewheeling current crosses zero for the first time, the maximum power frequency voltage that the gap can withstand without causing arc re-ignition is also called arc voltage.

6. Current capacity of the arrester: The arrester should have a certain current capacity, and its residual voltage should be lower than the impact withstand voltage of the protected equipment. After the arrester operates, when the specified lightning current passes through, the arrester should not be damaged. At the same time, the voltage drop caused on the arrester - the residual voltage - should be lower than the impact withstand voltage of the protected equipment. Otherwise, although the arrester operates, there is still a risk of breakdown of the protected equipment.

Of course, in addition to installing lightning arresters, it is also necessary to use some other combination of protection methods to protect against lightning strikes. like:

Establish an external lightning protection system consisting of lightning rods or lightning protection strips, lightning protection net down-conductors and grounding systems; power lines, signal lines, metal pipes, etc. must be connected at equal potentials through over-voltage protectors to eliminate destructive potentials caused by lightning Difference.

Transformer manufacturer reminds:

Thunderstorm season is coming, electrical safety issues cannot be ignored

Transformer manufacturer reminds: Thunderstorm season has arrived! In humid and rainy seasons, choosing reasonable lightning protection equipment is also a factor that needs to be considered when purchasing transformers. Here, we recommend that you choose a regular transformer manufacturer.

Our Leilang Electrical Appliances will configure lightning protection equipment according to your actual use needs and usage scenarios, select high-quality lightning arrester equipment, and rationalize the design to protect the safety of your equipment!

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