| Small current neutral grounding system is widely used in power distributionnetworks of6～66KV in China. As a result of this fault current is small, system with afailure can continue to work for a period of time. But for the fault current it is notobvious, it is difficult to selection the fault line for the small current grounding system.The current line selection of existing methods, practical application is not very ideal;it is difficult to meet the requirements of reliability for the fault line selection.Yet some operators still use the method of break and closing each line inshort-time to fine the fault line, although the line selection is very reliable, but for thesafe operation of power grid there are many unfavorable factors. Such as: theharmonic pollution, influence on the circuit breaker mechanical characteristic owingto the continuous action.Base on the analysis of a variety of the line selection principle. The paperintroduces a Single-phase-to-ground fault line selection method which namedcomprehensive strategy method. This method has stronger adaptability andfault-tolerant ability than single method of line selection. First, the application ofrough set theory for data mining and knowledge discovery of the fault samples, thedetermination of effective domain of all kinds of methods. Second in line selectionmethod based on the validity, integrated line selection using fuzzy theory to realize avariety of fault line selection method, and draws the line of each single fault degree.Finally the application of D-S evidence theory for single fault degree for effectiveintegration, to calculate the continuous fault degree, continuous fault degreemaximum line is the fault line.This paper introduces the design and development of the software and hardwareof the grounding line selection device. The device KA2003-DH has been applicationin0#110KV substation for some years. The fault line selection accuracy rate is veryhigh which are praised by the employee of the company. |
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