Differential Current Protection of Grid Connected Power Transformer with Zero Sequence Current Elimination

Abstract

The primary method of protection for power transformers is differential protection. The quantity and variety of defects grew due to the electricity network's fast growth. Zero sequence current (ZSC) going through the power transformer as a result of external line to ground faults causes the differential protection to falsely trigger. This technique tries to improve the differential relay's resistance to such errors in order to avoid erroneous trip decisions and keep protection reliability. To protect the transformer against unbalanced loads and other fault circumstances, the tripping system uses flip-flop logic-based controlling to create the trip signal. In the suggested method, flip flop logic-based current protection was used to reduce a zero sequence current in the primary side and secondary winding side during leakage and an earth fault. The zero sequence current flowing through the main or secondary winding of the power transformer is what this protection system depends on. Last but not least, the suggested technique is contrasted with standard differential current protection. The efficacy of a protective system is evaluated by looking at things like settling time, protection time, and circuit breaker operating time.