The arrester which uses zinc oxide semiconductor as a resistor material, such type of arrester is known as a metal oxide surge arrester or ZnO Diverter.
The device which is used for the protection of the equipment at the substations against travelling waves, such type of device is called lightning arrester or surge diverter. In other words, lightning arrester diverts the abnormals high voltage to the ground without affecting the continuity of supply. It is connected between the line and earth, i.e., in parallel with the equipment to be protected at the substation.
To protect the insulation and conductors of the system from the damaging effects of lightning
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.
|Type||System Rated Voltage (kV)||Rated Voltage (kV r.m.s)||Continuous Operating Voltage (kV r.m.s)||DC Reference Voltage (kV)||2ms Square Wave Current (A)||Residual Voltage(≤kVp)||Continuous Current Resistance Component mA(peak)|
|30/60μs Steep Impulse||8/20μs Lightening Impulse||1/10μs Operating impulse|