Research On Fault Diagnosis Method Of Power System Including Double Circuit Lines On The Same Tower

With the development and expansion of modern power system, the double circuitlines on the same tower are used widely as an important electric power transmissionmodel. Because there are a lot of cross-line faults which increase the type of fault，thefault diagnosis become very complex. The fault components topological connectiondiagram of the faulty component can form a ring network, which could cause thelogic infinite loop when use the traditional fault diagnosis model to diagnose doublecircuit lines and other special connections. The research on fault diagnosis of thedouble circuit lines is great significant.This paper proposed a fault diagnosis method based on six-sequence componentand expert system，which can analyze the fault on the double circuit lines quickly andaccurately. The main contents are as follows:(1) This paper proposes the concept of faulty components topological connectiondiagram, which can distinguish double circuit lines rfom the other structure mode.When a fault occurs，a group of suspected faulty components are built according tothe action information of circuit breakers and protection，and remove the duplicateelements. The diagnosis model of the suspected faulty components is built. Take thegroup of suspected faulty components as a starting point, search each connecteddirection, and establish the fault components topological connection diagram, whichdescribes the relationship between the faulty components and relevant protection andcircuit breakers in space and action logic. If the faulty component is a part of doublecircuit lines, the fault components topological connection diagram of the faultycomponent can form a ring network, which could cause the logic infinite loop whenuse the Petri net fault diagnosis model.(2) The analysis of the double circuit lines is dififcult, because there is mutualinduction not only between the phases but also between the lines in the double circuitlines. How to select the fault phase quickly and supply power uninterruptedly is animportant question. The six-sequence component theory is presented in order to solvethe question, which can eliminate the mutual induction. The currents of the six phases in the lines are switched into two separated systems, in which there is no line to linemutual inductance, then the symmetrical component method is used to eliminate thephase to phase mutual inductance and set up the positive negative and zero sequencenetwork, which compose the six-sequence mathematics model. The analyticalexpression of sequence currents and sequence voltages and composite sequencenetworks can be got by simultaneous equations of the boundary conditions andmathematics model. According to analyses the phase relationships of the sequencecurrents, the failure characteristics of the different types of failure can be got，whichprovide a theoretical basis for fault diagnosis of the double circuit lines.(3)This paper introduces the structure of the fault diagnosis expert system basedon above theories, and builds a framework of the fault diagnosis expert system whichincludes the knowledge base and inference engine. The knowledge base is builtaccording to phase relationships analysis of the sequence currents as above, whichinput the amplitude relations and the phase relationships between the six-sequenceinto the Access database. The inference engine uses forward reasoning with heuristicinference mechanism.(4)The simulation model in this paper illustrate that this fault diagnosis methodcan make a rapid and accurate fault diagnosis to power system which include thedouble circuit lines.From the above analysis, the fault diagnosis method built in this paper is inpossession of academic and actual use.