Analysis Of Specific Characteristics And Action Of HVDC Protection During Fault

Compared with HVAC transmission system, HVDC fault feature is more complicate and characteristic because of its converter device, control mechanism and operation mode. And this makes differences of protection relay performance characteristics between HVAC system and HVDC system. Converter and DC line are the two core components of HVDC system. They characterize the HVDC system well in fault analysis and protection principle. And their performance determines the reliability and efficiency of the whole HVDC system, so it has important implications for the optimization of protection and the stable operation of power grids to hold the behaviors of protection relay performance. But most of HVDC protection researches aimed at protection action of practice run and operation, so it is deficient to recognize the action characteristic of protection relay performance. But most of HVDC protection researches aimed at protection action of practice run and operation, so it is deficient to recognize the action characteristic of HVDC protection relay performance. Given this problem, we focus on the two components in this paper and do the research of the complexity of HVDC fault. And the specific characteristics and action of protection during fault are proposed.Starting from the operating principle of HVDC, the nature of complexity of DC system fault is pointed out three aspects as state of converter valves, regulation of control system and operation mode. Firstly it analyses the impact of state of converter valve on fault loop and presents time-space characteristic and diversity on two sides of converters. And the effect of control system on commutation failures and characteristic quantities of protection is given after analyzing adjustment function of control system during fault. It also points out that the diversity of operational condition could bring the difference of electric quantities and control parameters.On the basis of fault analysis above, the behaviors of HVDC protection relay performance under different faults is simulated by using an accurate simulation model accordant to the practice HVDC system. The characteristics of faults and the uncertainty of relay performance behaviors are concluded. With fault analysis above, the diversity of two sides relay performance, protection characteristics of boundary-fault, time discreteness of protection and the sensitivity change under different deep and operational condition are proposed. The behaviors and related regulars of HVDC protection relay performance under different faults type, position, faults resistance, faults occurring time and operational condition are illustrated in whole and can give a basis for the fault location of boundary, cooperation of protections and setting determination and optimization of protective relaying.This work is supported by the the National High Technology Research and Development Program(“863” Program) of China(No. 2012AA050209),the National Science Foundation of China(51377059) and the Science Foundation of Guangdong Province(S2013010012885). Some of the research results have been applied to the operation of actual HVDC systems, obtaining great economic and social benefit.