Analysis Of The Principles And The Improvement Solutions Of The Electrode Overvoltage Protection In The HVDC Project

Nowadays, HVDC has an obvious advantage in the long-distance and large-capacity power transmission and the power system interconnection, and plays an important role in the West to East Power Transmission Project. Its operation is very flexible, in that when a fault happens to a certain pole and causes the breakdown, the other pole is still able to operate, which can greatly reduce the negative effect on the system. On the other hand, the flexibility has a higher requirement to the DC protection system. The system must guarantee the normal operation of the non-fault pole when segregating effectively the fault pole. In the course of the commissioning and the operation of both Gui-GuangⅠ&ⅡHVDC, the electrode overvoltage protection once arose, which caused mono-polar blocking and bi-polar blocking in succession, seriously affecting the operation of the system. Therefore, it is of great significance to analyze and eliminate the logic bugs of the electrode overvoltage protection in Siemens HVDC technology, which can in turn greatly improve the reliability of HVDC system.The thesis focuses on the analysis of the principle of the electrode overvoltage protection of the Gui-GuangⅡHVDC Project, and proposes solutions for improvements. It first introduces the principle and the consequences of 59EL and its protection logic. Through analyzing events of 59EL in the process of commissioning of the Gui-GuangⅡHVDC Project, the paper then points out bugs in the current operating 59EL. In the following part, several solutions of improvements are proposed and compared. And finally, with the consideration of the practicability and RTDS simulations, the paper proposes the solutions to the modification of the logic of the Gui-GuangⅡHVDC's electrode overvoltage protection and the pole control system and DC station control system.These proposed solutions have been verified by RTDS simulations and on-the-spot experiments, and have been applied to HVDC as the anti-accident measure and achieved the ideal feedback.