Summary

Abnormal voltage controller which uses grounding transformer eliminates the problem of grounding fault protection system perfectly through it minimizes impact of Harmonics and surppress rising of electric potential by grounding transformer.

 It is possible to check ground currents by Ao Meter without checking insulation resistance directly and to carry out speedy action by cut-off power system by earth fault protection relay(OCGR) or by Alarm.
 

Purpose

 There are lots of accident dangers such as malfunction of control equipments, element damage of equipment as well as risk of electric shock by rising of electric potential (voltage) at the time of ground fault due to insulation damage & contact of electric between grounds, but it can prevent such accidents in advance as supress abnormal voltage by adoption of this controller. In general, Ground fault protection system in unground system which is adoped currently is dectecting the sequence voltage by CRL of it limits ground falult current by protection relay. However, unbalance voltage is applied on GPT 4th winding due to Harmonics which is generated at the time of switching by increasing adoption of power convertion device like inverter recently. So, there are occuring lots of problem which reduces reliablility of ground fault protection system by malfunction of ground fault protection system due to sequence voltage & image current is deteced even though ground fault is not occurred actually.