Adaptive Directional Relay and Direction Comparison Protection Based on Instantaneous Power for UHV Transmission Lines

The paper presents a directional relay and a direction comparison protection scheme based on instantaneous power for UHV transmission line, in which instantaneous passive power was defined using Hilbert transform. Using instantaneous active power and instantaneous passive power measured at the relaying point, the relay can determine the fault direction in very short time since the fault occurs, even in 2 ms. The operation time performance depends on the characteristics of fault generated travelling waves. If the fault occurs as the voltage is crossing zero, direction determination will be based on post-fault power-frequency voltage and current, and the operation time will be less than 20 ms. And the paper proposes direction comparison protection scheme integrated with the directional relay. Simulation studies show that the directional relay and the protection are with high speed operation, excellent reliability, sensitivity, and adaptability, and it is an ideal protection of UHV transmission lines.