Utilizing Rogowski coil for saturation detection and compensation in iron core current transformer

Saturation of conventional iron core current transformers (CTs) may cause mal operation of protective relay. This paper proposes a hybrid scheme that intends to utilize Rogowski coil (RC) along with conventional iron core CT to detect and compensate fault current fed to protective relay. The main reason of utilizing RC is due to linear behavior of core characteristic. Proposed scheme is implemented using statistical similarity index based on residual error of CT and CR outputs. This index has inherent immunity against noise. This combination will result in prevention in mal operation of protective relays that especially use fault current in their decision making. Several case studies have been conducted to simulate and investigate the performance of proposed scheme under different conditions. Results show that proposed scheme can deal with realistic circumstances that cause CT saturation.