Optimal coordination of directional overcurrent relays using interval analysis method

Abstract

When two protective apparatus installed in series have characterist ics, which provide a newlinespecified operating sequence, they are said to be coordinated or selective. The newlinecoordination of directional overcurrent relays pose serious problems in the modern newlinecomplex power system networks, which are interconnected. Overcurrent relays (OCRs) newlineand Directional overcurrent relays (DOCRs) are widely used for the protection of radial newlineand ring sub transmission systems, and distribution systems. Directional overcurrent newlinerelaying is mainly used for the primary protection of ring distribution systems as the newlinesame magnitude of fault current can flow in either direction. They are also used for newlinesecondary protection in transmission systems. Relays in different locations will detect newlinegreatly different currents during the same fault. The relay coordination problem is to newlinedetermine the sequence of relay operations for each possible fault location so that the newlinefaulted section is isolated to provide sufficient coordination margins without excessive newlinetime delay. The ultimate objective being improved power system reliability and the newlinecalculation of the Time Dial Setting (TDS) or Time Multiplier Setting (TMS) and Pick newlineup current p) setting or Plug Setting Multiplier (PSM) of the relays is the core of the newlinecoordination. The main aim of this research work is to develop new objective function newlinewhich would be used to solve the DOCR coordination problem. An optimization newlinetechnique based on interval analysis would be developed for optimal coordination of newlineDOCRS.