An improved protection scheme of the ground electrode line based on two frequency components injection

摘要

The ground electrode line plays an important part in the high-voltage direct current (HVDC) systems. For the protection of the ground electrode line, the electrode line impedance supervision system is designed. However, the system has a dead zone problem. And the existing analysis on the protection scheme is not complete, because the model used in the analysis is not accurate. Therefore, an accurate analysis of the measured impedance under the normal operation and different types of faults was given in this paper, to find the property of the impedance. Based on the derivation, an improved protection scheme was proposed, which mainly consists of the injection of the signal of two frequency components to eliminate the dead zones of each other, and the frequency selection criterion. The dead zones can be eliminated greatly with the proposed scheme, and the proposed scheme has a high reliability and a strong ability to endure high transition resistance, which was verified by lots of simulation cases based on the PSCAD/EMTDC.