Incorporating Overcurrent and Overflux Protection for Transformer using Different Time Characteristics

this paper presents the protection for transformer using different time characteristics. To design and develop a protection system for transformer which automatically respond to the over flux based on the definite minimum time(DMT) and inverse definite minimum time(IDMT) characteristics and over current based on the standard inverse(SI), very inverse(VI) and extreme inverse(EI) characteristics. Therefore, over-current relays must de-energize the faulted line as fast and accurate as possible to protect the system from the hazardous effects of the fault. The relay acts based on the program inbuilt to each characteristic. In order to prevent mal-trip of relays resulting from these transients, a longer delay is not initiated for relay trip command. Self checking facility of the occurrence of the fault time is incorporated in the programs which are used in individual relay characteristics.