Power surge arrester installation principle

Among the lightning protection projects, there are many disputes regarding the installation location and type selection of the power surge arresters. The author combines these years' work experience and the theory of lightning protection to elaborate some of his own opinions:

Class B arrester (installed in LPZ0A area)

1. Installation Principle Theoretically, the first class arrester (Class B) should be installed at the front of the total incoming line. If it is inconvenient to install, it can also be installed at the open back end. However, if there is a dual power switching device at the front of the line, it must be installed at the front of the dual power switching device, so that the switching device is protected (the current dual power switching devices are mostly mechanical and electronic control type, and some have 232 And 485 control devices and 24 volt fire-fighting power supply, lightning current once passed, it is easy to damage). The reason is that the operation time of the air breaker (circuit breaker) is much longer than the operating time of the arrester. Once a lightning current (overvoltage) passes, the arrester will move ahead of the circuit breaker action and discharge the overcurrent to protect the circuit. And its back-end electrical equipment.

2. Selection Principle B-type arresters try to select the voltage switch type arrester. The flow capacity is large, and the protection voltage UP should be as small as possible. The front end of the general arrester should be connected in series with a circuit breaker with a corresponding capacity. The function of the circuit breaker is to facilitate replacement when the arrester is damaged. The second is to avoid current-to-ground faults when the arrester ages.

Class C arrester (installed in LPZ1 area)

1. Installation principle The limiting arrester can be installed in parallel on the front or back end of the secondary power supply air circuit breaker, and the front end of the arrester is connected in series with the circuit breaker of the corresponding capacity. The effect is the same as above.

2. Selection principle The C-type arrester adopts the pressure limiting type, and the residual voltage generated after the B-type arrester is turned on is controlled below the impact insulation level of the device. Since the corresponding time of the voltage limiting element is fast, it is generally about 25 ns, and the corresponding time of the discharge gap is relatively slow, about 100 ns. Therefore, before the class C arrester is turned on, the class B arrester should be turned on first. This must be to ensure a certain installation distance between Class B and Class C. Theoretical Analysis (Calculation of Inter-SPD Level Coordination—Using Traveling Wave Theory for Overvoltage Analysis), see (http://)

Class D arrester

Same as above

The role of Class B arresters is mainly to discharge the amplified current. The role of Class C and Class D arresters is mainly to limit the residual voltage of Class B arresters below the withstand voltage level of back-end equipment to protect the equipment.

Class C and D surge arresters should be installed as close as possible to the protected object.