DESIGN AND EVALUATION OF A CIRCULATING CURRENT DIFFERENTIAL RELAY TEST SYSTEM

This paper describes how an EMTP based simulator can be used in conjun ction with a relay test set to type-test a protection relay operating within a circulating current differential protection scheme. The combi nation of a simulator and a test-set is designed to replace a high pow er synthetic test plant that has been used for more than 30 years for type and approval testing of differential protection relays. The paper will include results that describe the operating performance of the n ew test system, on both internal and external faults, and these will b e compared with experimental results obtained fi om an identical set o f tests on the synthetic test plant.