The impact of current transformer saturation on the distance protection

The distance protection relay measures the line voltage and line current at the relay location and evaluates the ratio between these quantities. Distance relays are widely used on transmission, and even distribution systems. Current transformers (CT) are the very important part of the power system protection. The main purpose of a CT is to transform the primary current in a high voltage power system to single level that can be handled by delicate electronic device. This paper deals with the influence of CT saturation on distance digital relay. Saturation of the CT is evaluated for fault close to the relay location.