Computer aided design of IDMT relay settings and performance for interconnected power systems

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Overcurrent Inverse Definite Minimum Time (ID MT) protection is widely used on distribution and subtransmission circuits as both ain and back-up protection. When the systems are tightly looped, as is often the case, coordination of ID MT relays becomes very complicated and time-consuming. Each relay must be set so that it not only recognises a fault but also operates discriminately in a proper time sequence with the relays on neighbouring lines. Frequently, changing a single relay set ting or adding another line to the system may effect the whole relaying system, and repeated set ting modifications and coordination checks throughout the system are then required. In addition to all these, the short-circuit currents ecessary to check coordination are needed to be calculated too. So why, at this age of automation, these tedious and time-consuming relay set ting prediction and time coordination checks should not be transferred from the relay engineer to the computer ?The idea behind this project is to develop: 1) A suitable fault study routine \ 2) A procedure by which the relay settings are determined.3) An assessment of the performance of the predicted settings by system fault simulation.