Microprocessor based harmonic restraint differential protection scheme for a transformer

Abstract

This paper presents a microprocessor based differential protection scheme for a single phase transformer with harmonic restraint feature to avoid mal-operation during inrush current conditions. The protection scheme is implemented by means of a single microprocessor of intel's 8088 type. The relay has been tested satisfactorily by an arranged circuit for differential protection of a test transformer in the laboratory for the above condition. The test results indicate that the relay detects the inrush or other abnormal conditions satisfactorily within an overall time of about 26 μs. © 1992.