Study On The Method Of Fault Section Location Of Distribution Grid Based On Fault Database

While the structure of the distribution network become more and more complicated, the enterprises and people’s daily life have higher requirements to the reliability of the power’s distribution, thus a higher claim to the distribution automation come to us. Faults-locating is an important function of the distribution automation system, the aim of it is find the fault area and isolate it quickly to provide technical support for restoring power of the non-fault areas as soon as possible.The single-phase ground fault occurs more in the distribution network, the two-phase and three phase faults occurs less but it’s more harmful. This paper summarized the traditional distribution network fault-locating and ranging methods of the world, learned from the ideas of the distance protection, analyzed the two-phase and three phase fault-locating methods and designed the faults sections locating database on this basis, the main process is as follows:1、According to the basic principle of the distance protection, analyzed the basic theory of the fault distances’calculating which calculated by the impedances on the distribution network sections. On this basis analyzed the methods of the fault-judging when the fault information is inadequate. According to the voltage and the current which measured in substation side and feeder ends, calculated the values of the voltage and current of the fault branch’s both ends by iterative algorithm, and calculated the fault distance, meanwhile, analyzed the affections caused by the loads’fluctuation and the transitional resistance to this method through simulation.2、The method of the fault distances’calculating is calculated on the fault branches, so the first of all is determining the fault branches. This paper proposed a method which could locate the sections of the fault in distribution network based on fault simulation database, the main processes are:analyzed the51nodes distribution network system, designed its equipment information into a database; used PSCAD to simulate the different fault (like two-phase phase-short-circuit fault、two-phase ground-short-circuit fault、three-phase phase-short-circuit fault and three-phase ground-short-circuit fault and so on) happened on every nodes, measured the impedance modulus on the monitoring points by changing the value of the transitional resistance; formed the branch-impedance-modulus range by the value of the transitional resistance and the branches, and then designed the impedance-modulus database by Microsoft SQL Sever2008.3、Affected by the transitional resistance, matching the measured impedance modulus and the impedance modulus database could leads multiple suspected fault sections. To solve this problem, this paper analyzed the theory of the impedance angle, proposed using the cotangent of the impedance angle to measure the value of the transitional resistance and established the cotangent of the impedance angle database. When fault happens, determine the type of the fault by the values of the voltage and current that measured before, match the measured impedance modulus in the impedance modulus database and get the suspected fault sections, then, match the measured cotangent of the impedance angle in the cotangent of the impedance angle database, fine judge the suspected fault sections, exclude the non-fault sections.