Research On Improving The Success Rate Of UHV Single-Phase Automatic Reclosing

Developing UHV transmission is an effective mean to solve the imbalance problembetween the development of economic and distribution of energy in our country, thisrequires higher security and reliability of UHV power transmission system as well. UHVautomatic reclosing is the significant equipment which guarantees the system operatingsafely and reliably, therefore there is an important practical significant to study how toimprove the operation success rate of the UHV automatic reclosing.From the system’s point of view,based on extra-high voltage projects of the south ofZhejiang-the west of Shanghai and Jindongnan-Jinmen-Nanyang, the paper adopted themethod that combines the theoretical analysis and simulation to study the zero drift of shortcircuit current, recovery voltage of circuit breaker, secondary arc, and the identificationability of automatic reclosing.Firstly, the cut-off process of automatic reclosing has been studied. According to thetheory of electric arc, the model of arc of circuit breaker has been proposed, which is usedto calculate and analyze factors affect the zero drift of short circuit current and recoveryvoltage of circuit breaker.In order to improve the cut-off ability of automatic reclosing, theeffective measure to limit the zero drift of short circuit current and recovery voltage ofcircuit breaker has been found out.Secondly, two key problems in the reclosing process of circuit breaker have beenstudied: one is how to limit the secondary arc; another is how to identify the faults of circuitbreaker.The mechanism of secondary arc generation and the restrictive measures have beenanalyzed in the paper. The paper focuses on the effects of rapid grounding switch andinstalling the small reactor in neutral point to restrain the secondary arc and the conditionof application for the two methods. Besides, installing the rapid grounding switch piecewise to restrain the secondary arc has been proposed, and the best value of neutral small reactance has been given out.Finally, the fault identification method of automatic reclosing for UHV transmission lines with shunt reactor has been studied. The voltage amplitude ratio between terminal voltage of fault phase and neutral small reactance voltage is different for transient or permanent fault, which can be a criterion that can distinguish the fault type, transient or permanent. Additionally, the paper has proposed the method that delays a beat frequency oscillation cycle to decide the fault types for the existence of beat frequency oscillation will cause misidentification on transient fault, which can improves the reliability and accuracy of the identification result.