Use of Rogowski Coil for accurate measurement of secondary current contaminated with CT saturation in distance protection scheme

Due to inherent linearity and wide operating range Rogowski Coil (RC) can be used as a current transducer in electrical power system. This paper presents use RC for accurate measurement of secondary current to prevent under reaching of the distance relay caused by saturation of conventional Current transformer (CT).Conventional CT, lumped parameter RC with integrator and distance protection scheme is modeled and simulated by using Power System Computer Aided Design (PSCAD) software. The level of CT saturation is varied by changing the CT secondary burden and the fault instant. The results given by use ideal CT, conventional CT and Rogowski coil in distance protection scheme are compared and discussed. It is observed that use of RC as current transducer will behave as ideal CT and completely overcome the under reaching issue of the distance relay.