Research Of Fault Line Detection Based On Wide Area Relaying Protection

Along with the development of society, our nation had been set up strategic objectives of “national grid, power transmission from west to East, North South mutual supply”. Electric power users have been increasingly strict on electric power reliability, but the faults of electric power system especially transmission systems couldn't be inevitable. It is important to find out fault accurately. The traditional researches of fault detection are mostly based on digital information(the status of protection and circuit breaker). The location, region, type, error actions and refused actions of fault component could be judged by the states of protections and breakers obtained and the experience of dispatching personnels. It is really important to detection fault components. But only digital informations are used in those detection methods above, the procedure of fault occurring could be recorded by the analogue information(the waveforms of current and voltage). As is known to all, there are uncertain factors in digital informations, however, the analogue information has the enormous advantages.This thesis from the three aspects of phasor measurement, fault correlation degree and distribution of voltage to carry on the research of fault detection:(1)The phasor measurement approach is alternative fault detection approach independent of the function of protection system, utilizing PMU data and bus impedance matrix(Zbus). First, the proposed method diagnoses the fault area, and next the fault line is diagnosed. Fault location along the diagnosed line is also estimated by wide-area measurements. The proposed method is applied to the IEEE 118-bus test system where the results indicate successful detection of the faulted lines throughout the grid as well as wide area fault location along the faulted line.(2)The fault correlation degree detection approach is on the basis of the determining the fault correlation region, this thesis proposes a fault location method based on the fault correlation degree. Under the normal condition of the power system, the system network corresponding matrix is listed. After the system fault occurred, solve the fault correlation degree of each branch, through the testing and calculation can locate fault location accurately. This method can not only determine the location of the fault line, but also can determine the specific location of the fault components, without change the correlation coefficient matrix, solve the uncertainty problem of the correlation coefficient matrix after fault, the transition resistance and fault type does not impact on it, the calculation is relatively simple, and the positioning is accurately. The simulation results showed that this method can accurately verify different locations and different types of fault.(3)The distribution of voltage detection approach is used the value of fault voltage and fault current measured from one side of the line to estimate fault voltage of the other side of line. The ratio of estimated value to measured value makes up the protection criteria. It isn't affected by transition resistance, and it wouldn't misoperate when flow transferring caused by overload happened. The principle of this algorithm is simple and it requires little information. It has little request on the synchronization of the information from different sides and is convenient to implement. The simulation proved that the algorithm can successfully distinguish the faulted line under different type of faults.