基于Markov模型的高压输电线继电保护装置风险评估

Research on Markov Model Based Risk Assessment of Protective Relaying for High Voltage Transmission Line

评估运行中的继电保护装置可能引起的后果,是继电保护评估的一个重要问题。结合线路状态和保护装置失效机理,提出了高压输电线继电保护装置风险评估方法。首先,给出输电线与保护的10种状态;进一步,根据保护的自检特性,归纳获得了由保护装置引发的4种风险,即显性误动风险、显性拒动风险、隐性误动风险和隐性拒动风险。然后,根据输电线路和保护装置的状态划分,建立10状态Markov模型,并利用Markov模型给出上述4种风险指标计算方法;最后,基于某电网实测数据,对比了风险与传统可靠性指标在评价可靠性上的差异,分析了自检率对风险的影响。分析表明,风险与不可用率随定检周期变化差异明显,降低失效率或增大自检率能有效地降低系统风险与不可用率。

It is of significance for the assessment on protective relayings to evaluate possible consequences caused by being operated protective relayings. Combining with the state of transmission lines and the failure mechanism of protective devices, a risk assessment method of protective relayings for high-voltage transmission lines is proposed. Firstly, ten states of overall system composed of transmission lines and protective devices are given and further according to the property of self-checking of microcomputer-based protective devices, four kinds of risks, namely the detected unready operation failure, the undetected unready operation failure, the detected unnecessary operation failure and the undetected unnecessary operation failure, are concluded. Secondly, according to the division of the states of transmission lines and protective devices, a 10-state Markov model is established, and using this Markov model a computing method for above-mentioned four kinds of risk indices is given. Finally, based on the measured failure data of protective devices in a certain power system, the differences in evaluating reliability by the proposed risk indices and traditional reliability indices are compared, and the impacts of self-checking rate on risks are analyzed. Analysis results show that there are obvious differences of both risk indices and unavailability that change with the cycle of periodical survey; the risk indices and unavailability of the system can be effectively reduced bydecreasing the failure rate or increasing the self-checking rate.