The uniform formula of single phase earth - fault distance relay with compensation

The single-phase earth fault is the most common fault type on high voltage transmission line. But the sensitivity of single-phase distance relays can´t satisfy the requirement of power system. In order to improve the sensitivity of distance relays to protect the single-phase faults with large earth resistance, one uniform formula is provided to express most of the single-phase distance relays in this paper. More than ten kinds of relays that have been used widely can be expressed by the uniform formula through giving different coefficients. This simplifies the expressions of conventional relays. The uniform formula is helpful to analysis the performance of these relays. It also provides an approach to create new relays with better performance or to lucubrate the correlative principles. Two new relays based on the uniform formula are proposed in this paper. Simulations show that the new relays have better performance than the old ones. At last, the fundamental about the choice of polarization voltage is discussed.