What Do You Know about Surge Arrester?

The role of surge arrester when the surge overvoltage along the overhead lines into the substation or other buildings, will occur when the flashover, and even the insulation of electrical equipment through. Therefore, if the power supply of electrical equipment into the end and connected to a protection device that surge arrester, when the overvoltage value reaches the specified action voltage, the arrester immediately act, flow through the charge, limiting the overvoltage amplitude, to protect the equipment insulation; voltage value is normal, the arrester and quickly restore the original state, to ensure that the system normal power supply.

The protective effect of the surge arrester is based on three premises:

1. Volt-second characteristics and the volt-second characteristics of the protected insulation have a good match

2. Ensure that the residual voltage is lower than the shock electrical strength of the protected insulation

The protected insulation must be in the surge arrester protection distance within the requirements of the arrester:

1. Normal operation is not discharged, over-voltage discharge correct action.

2. To have a self-recovery function after discharge.

Surge arrester related parameters.

1. Continuous operation voltage: i.e. allow long-term working voltage. It should be equal to or greater than the highest phase voltage of the system.

2. Rated voltage (kV): i.e. the maximum permissible short-time working frequency voltage (arc extinguishing voltage). Surge arrester can act in this frequency voltage discharge and extinguish the arc, but not in this voltage long-term operation. It is the arrester characteristics and structure of the basic parameters, but also the basis for the design.

3. Frequency withstand volt-second characteristics: indicates that the zinc oxide arrester in the specified conditions, the ability to withstand overvoltage.

4. Nominal discharge current (kA): used to divide the arrester level of discharge current peak. 220 kV and the following system should not exceed 5 kA residual voltage: refers to the arrester in the impact current, the arrester ends of the voltage generated can also be understood as the highest voltage value that the arrester ends can withstand.

The arrester uses zinc oxide semiconductor as a resistor material, such type of arrester is known as a metal oxide surge arrester or ZnO Diverter. This arrester provides protection against all types of AC and DC over voltages. It is mainly used for overvoltage protection at all voltage levels in a power system. 

The metal oxide surge arrester has the following merits:

1. It eliminates the risk of spark over and also the risk of shock to the system when the gaps break down.

2. It eliminates the need of voltage grading system.

3. At the normal operating condition, the leakage current in the ZnO is very low as compared to other diverters.

4. There is no power follow current in ZnO diverter.

5. It has high energy absorbing capability.

6. ZnO diverters possess high stability during and after prolonged discharge.

7. In ZnO diverter, it is possible to control the dynamic overvoltages in addition to switching surges. This results in economic insulation coordination.

The information is provided by the surge arrester supplier.