| Hidden failure of relay protection is one of the culprits causing the large-scale power outages. Although the probability of such incidents is little, they are of great harm. The event will trigger a cascading reaction of power system and spread rapidly once it occurs, ultimately lead to the collapse of power system, and bring about disastrous consequences. As the interconnected system capacity increases and voltage rating improved, hidden failures of relay protection will jeopardize the safety of power system more and more. Therefore, assessment and analysis of hidden failures are of great theoretical and practical significance to guarantee the safe operation of power system. Creating hidden failure monitoring and control system is an effective way to prevent hidden failures, and is technical trend of the world. As an intelligent automation device monitoring security operation of the power system, fault recorder records the behavior of the relay and automatic device, and with the recorded waveform and data, deficiencies of relay and automatic device will be found promptly, which is of great significance for the achievement of hidden failure monitoring system. However, fault recorder does not start wave-recording except in the event of power system large disturbance. In order to provide more complete and valuable field data for the research of hidden failures, this paper also studies the records of power system disturbances.This paper reviews the research states of relay protection, hidden failures and fault recorder at home and abroad, focuses on several key issues such as the probability of hidden failures' incorrect line removal and the criterion of starting disturbance recording. Main research work and the results obtained are as follows:â‘ By searching several typical cases of big blackout, the fact that much power outages is due to the incorrect actions of protection systems is pointed out, and relevant knowledge and research theories of hidden fault are introduced.â‘¡The regions of vulnerability of hidden failures are defined by analyzing the action mechanism of the hidden failures in protection equipment. And probabilistic model, for hidden failures' incorrect line removal, is established by utilizing the calculation of the hidden failures probabilities of protection equipments and the fault probabilities of regions of vulnerability. This model can evaluate the probabilities of hidden failures' incorrect line removal of protection devices with different principles and the entire protection system, and consider the effect which transmission lines with different fault probabilities have on triggering the hidden failures in protection equipment.â‘¢The methods of hidden failure monitoring using power system information are introduced, the feasibility of power system disturbance recording is analyzed and regular disturbance signal detection methods are evaluated.â‘£The concepts of parameter identification and forecasting methods are introduced into power system disturbance detection against the existing problems. Proposes a real-time disturbance detection based on adaptive forecast method from the perspective of waveform distortion and implements the computer program. The result for a wide range of disturbances shows that the proposed method can effectively detect the distortion points and can make real-time and accurate detection of a variety of disturbances, including Oscillation, frequency deviation and harmonic etc. |
