Font Size: a A A

Study On Earth Fault Detection In Distribution Network

Posted on:2007-03-15Degree:DoctorType:Dissertation
Country:ChinaCandidate:H F ZhangFull Text:PDF
GTID:1102360185984116Subject:Power system and its automation
Abstract/Summary:PDF Full Text Request
In China, the non-solidly earthed neutral is widely used in distribution system. It has the virtue of proving power supply's reliability. But faulted feeder selection and fault location are not solved when single-phase to earth fault occurs due to weak current and unstable fault arc. To date utilities still use manual switching to identify an earthed feeder and eyeballing to locate the fault point in the absence of a more reliable detection method. So, this paper studies faulted feeder selection and fault location in distribution system.To make the best use of fault information, synthesizing many kinds of fault selection criteria based Rough sets theory is proposed. The criteria based steady state component, transient component and additional diagnosis signal are integrated on the validity. The main tools of the method are information table and decision table. The fault characteristic quantity with each selection method is extracted from the original data and discretized. To get the fault information table, we should make the feeders on the busbar as universe, make the selection criteria as condition attributes and make the discrete fault characteristic quantity as attribute value. Then we should reduce the universe, form the decision table by decision rules, and find the faulted feeder from the decision attribute of the decision table. In the whole process, only the original fault data is needed. The faulted feeder can be identified without experiences and human work. The simulation has proved its advantage.In terms of practice, the paper provides the selection method based projection value of zero-sequence current, which has nothing to do with polarities of zero-sequence voltage and zero-sequence currents. This method makes the line of zero-sequence voltage as reference axis. The fundamental zero-sequence current of each feeder projects on the reference axis. To Peterson Coil neutral system and resistance neutral system, zero-sequence current of each feeder projects on the axis directly. To theungrounded neutral system, phase of the zero-sequence current shift 90°, then project on the axis. No matter how the polarities of zero-sequence voltage and zero-sequence...
Keywords/Search Tags:Distribution network, single-phase to earth fault, fault detection, power system transient, power system steady state, signal injection method, distribution automation, Rough set theory
PDF Full Text Request
Related items