| Given to the interconnected power grid, HVDC is mainly used in long distance and high capacity transmission.The regional power grid more closely linked, can be put to more effective use of energy, but also new challenges to the security and stability of power grid, in the event of failure, may result in very serious knock-on consequences. Relay protection for high voltage DC transmission system’s first line of Defense, its reliability is essential to the research. DC system research started late, its reliability studies are not mature enough, but with the project put into operation, the reliability of the gradually exposed, their protection and control system reliability problems is particularly evident. Scholars currently run on DC protection exposure problems in some studies, but it is in simple statistical and qualitative analysis phase. This study on reliability assessment of HVDC transmission line protection, the main contributions are as follows:Firstly,analyzes the reason of DC transmission line protection using traveling wave protection, introduced the principle of travelling wave protection in transit.Then, according to the principles of protection, DC circuit protection rejection probability calculation method is proposed. Is different from the statistical data protection hardware failure calculation, based on the principle of protection criteria, analysis in principle cause reliability problems may occur in the process, based on the principle of reliability, protection rejection probability calculation method is proposed. Based on actual operating data and protection of DC system configuration (sampling frequency, the setting value, the protection principle), calculation of metal ground fault of DC circuit protection the rejection probability analyzed different fault rejection rate trend; analysis of protective effect of configuration on rejection probability.Furthermore,DC circuit protection malfunction probability calculation method is proposed. Malfunction of protection analysis, building the method of calculationprotection maloperationprobability caused by lightning strike. In the same system, the calculation of direct lightning (regardless of Lightning) protection maloperation caused by probability analysis under different amplitude of lightning current and trend of different probability of lightning strike location of maloperation analysis under different protection, lightning protection maloperation caused by probability. Similar to calculating the probability of lightning malfunction, analysis of other events that may cause malfunction to impact protection maloperation probability.Lastly, combination of hardware failure, DC circuit protection risk assessment model is established. Software failure (principle of reliability) and hardware failure (reliability of the device itself) of the different status, Markov model of DC circuit protection systems established, by evaluating the presence of impact and probability, established DC line protection risk assessment calculation method. Combined with concrete examples, analyzing the impact of risk protection configuration for line protection. |
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