On-line Monitoring And Diagnosis Technology Of Hidden Failure Of Protection System

With the enlargement of power system scale, the security and stability requirements of power system are also increasing. However, due to some inner reasons and the impact of the external disturbance, problems of relay protection system that is the first line of defense for power system are more and more prominent,this also brings power system stable operation and social development serious influence. According to the survey, hidden failure of protection system is an important factor to promote cascading failure. Therefore, the study of mining and identification as well as early warning and prevention technology of hidden failures in relay protection system becomes an important and urgent issue and has great value to ensure the safe and stable operation of power system.Firstly, based on lots of reference relating to the subject, a brief introduction is provided to uncover the concept, cause and performance of hidden failures. Based on this, the paper summarizes the present research methods of hidden failure, then explores vulnerability analysis and risk evaluation methods as well as monitoring and control strategies of hidden failures. By identifying hidden failures incentives, combined with the large-scale blackout, a systematic classification of hidden failures in relay protection is studied. The kind of hidden failures that caused by the equipment failure is monitored and identified. The hardware defects of high voltage circuit breaker and DC operating circuit are analyzed. Aiming at these two problems, the corresponding on-line monitoring and diagnosis methods are put forward to solve above two kinds of hidden failures.By analyzing the working characteristics and operating process of secondary circuit and operating mechanism of high voltage circuit breaker, a tot of available information is discovered contained in coil currents and contact states according to operating features. A new method for fault diagnosis of high voltage circuit breaker based on least square support sector machine and the opening/closing coil current of high voltage circuit breaker is presented. The method can accurately identify a variety of hidden failure types and provide the basis for hidden failure location and condition-based maintenance of high voltage circuit breaker.By analyzing the principle and characteristic of DC operating circuit, aiming at the key problem of DC operating circuit, a new method of on-line DC operating circuit monitoring and early warning was presented. The current of the trip circuit or closing circuit is on-line monitored to realize disconnection monitoring of the trip circuit and closing circuit simultaneously. Meanwhile, time relay is added to the trip circuit or closing circuit to monitor its situation and avoid burning of breaker trip coil or closing coil. Based on the actual line protective devices, this paper discusses the parameter tuning methods and components' selection of monitoring devices. Finally, the test is provided to prove the correctness and effectiveness of the presented method.