ADR221B is second generation Numerical Integrated Over Current Relay for Traction Application. It consist all the necessary protection and monitoring functions required for LV side and HV side of Traction Transformer Feeder.The High speed Digital Signal Controller is 16bit fix point DSP having all the features of DSP and microcontroller thus commonly known as DSC (Digital Signal Controller). The DSC continuously monitors current and REF current, along with different status input, through CTs, and optical isolated status connections. The high-speed microcontroller samples these signals through a A/D converter.