| With the rapid development of high-speed railway, a higher demand on the safe and stable operation of the traction power supply system has been put forward. Reliable operation of such secondary equipments as transformer and protection in plays an important role in traction power supply system. Analysis the traction power supply system fault records over the years, the incorrect action proportion of the protection devices stays a high level, which hidden failure not immediately removed is an important reason to cause a system failure extending. Currently, the study of power system hidden faults has been valued by some scholars, which mainly concentrated on the assessment of their probability of occurrence. The study of diagnosis and status monitoring for secondary equipments hidden fault is not involved. Based on this, considering the traction power supply system load changes frequently, researching in online diagnosis and early warning for hidden faults of traction substation secondary equipments is of importance and meaningful significance.Different from the traditional fault, hidden fault has significant harm with the feature of hidden and the need for trigger conditions. Firstly, traction substation secondary equipment hidden fault has been classified, and the difference of hidden fault and traditional fault has been clarified. Considering the secondary equipment measure values have the interrelated characteristics, hidden fault can be monitored.Transformer needs high reliability to provide the correct measurement values for detection and protection. When the transformer has hidden failure, the inaccurate measured values caused by waveform distortion will affect the sensitivity of protection, resulting in protection devices refusing to operate or mal-operating. In this paper, take the current transformer (CT) for example, according to Kirchhoff’s current law (KCL) and the traction power supply system topology, the current constraint relation between each branch of CT associated is constructed in form of matrix to obtain the analytical current value of every CT. Using the analytical and measured values of similarity coefficient to establish voting rules by the law of the impact of hidden failure to achieve CT hidden online fault diagnosis. The method is based on PSCAD/EMTDC simulation, regardless the impact of system load current fluctuation.The current-voltage characteristics of the different types of fault protection devices will take a different protection algorithms, the measured values of the sampling analysis and protection setting value is compared to choose whether or not action. That the measurement circuit measuring element such as time components and impedance element has a hidden failure will directly affect the reliability of protection. In this paper, the feeder distance protection, for example, the relationship of distance protection measure impedance has been analyzed with different locomotive operating conditions and different places of double-track AT and singlet AT power supply. The hidden fault diagnosis criterion simulation verifies its effectiveness in PSCAD/EMTDC.The purpose of secondary equipment online diagnosis is to find hidden fault and warning in advance. In this paper, the inadequate of current method of secondary device status detection has been analyzed, and the frame of traction substation secondary equipment failure warning system has been build. The study focus on multi-source data acquisition and processing technology, equipment status assessment, fault warning technology and the protection of maintenance decision-making techniques, which provides a good theoretical basis for hidden fault further study. |
