INVERSE DEFINITE MINIMUM TIME RELAY COORDINATION IN RADIAL TRACTION SYSTEM

For stable and reliable operation of power system, the coordination of relays plays an important role. In order to achieve fast and selective protection, the relays are to be coordinated through appropriate relay settings with correct grading margins. Relay settings are to be done at upstream and downstream in such a way that proper coordination is achieved along various series networks. This paper presents different factors which play major part in selection of Inverse Definite Minimum Time (IDMT) over current protection on radial network. The selection of IDMT curves and procedure applied in relay settings such as Plug setting multiplier (PSM), Time settings multiplier (TSM), grading margins and different techniques used in relay coordination in a traction system are discussed.