Enhanced Summation Impedance Relay for EHV Transmission Lines

For the safety and stability of EHV transmission lines, the identification and isolation of high-resistance single-line-to-ground faults have increasingly been a focus of research. However, the existing protection schemes have shown limitations in different aspects when the fault resistance is extremely high. To solve this problem, an Enhanced Summation Impedance Relay (ESIR) is proposed in this manuscript. An adaptive threshold is set by using the double-end absolute values so that the ESIR can trip the internal fault independent of the data synchronization. Under the open-phase operating conditions, the sound phase ESIR holds sufficient capability against high-resistance faults. Simulation and comparison studies show that the proposed ESIR can work in parallel with several types of existing main protection elements to supplement them to improve high-resistance fault detection. This cooperation enables enhancement of the sensitivity and operating speed of the line protection.