Protection scheme of cross differential relay for double transmission lines

This paper presents the development of the cross differential relay. The new relay is suitable to double circuit HV transmission lines. Based on basic principle of cross differential relay, the paper introduces a percentage cross differential current elements used to improve sensitivity of cross differential relay. To improve stability of cross differential relay, voltage elements are used to distinguish between fault and open circuit condition, and phase selector elements are used to block healthy phase elements. EMTP simulations and real time digital simulator system (RTDS) tests prove that the cross differential protection is able to offer correct responses under various system and fault conditions.