Arc short circuit is one of the serious faults in medium and low voltage switchgear. Due to the arc resistance, the short circuit current can not reach the setting value of over-current and quick break, so it can not cut off the fault quickly. The result of continuous arc combustion is the release of huge energy. In addition, the arc short circuit fault of the switch cabinet is often not cleared in time, resulting in disastrous consequences.

The arc protection installed in Hydropower Station adopts double criteria of arc and current. Only when the arc is detected and the current meets the fixed value, the arc protection will act. Only when the arc is detected or the current reaches the fixed value, the arc protection will only issue alarm signal.

The arc light sensor is installed in the bus room on the top of the switch cabinet, but it can't detect the faults of the cable head, support insulator and other high-risk parts in the cable room. If the arc light sensor is added, the comprehensive protection and detection of the switch cabinet can be realized, and the reliability of the protection can be increased. In order to avoid false alarm of arc light protection, the arc light sensor cannot be installed in the position which is easy to be illuminated by strong light.

Arc protection principle is simple, fast and reliable, can effectively solve the harm caused by fault arc, reduce equipment losses and casualties, ensure the safe and stable operation of power equipment, improve the reliable operation and economic benefits of power system.