Inter-Turn Fault Detection in Power transformer Using Wavelets

Detection and removal of incipient faults in power transformer winding is essential because minor faults may develop and lead to major faults and finally irretrievable damages occur. This research article presenta a new, simple and incipient fault detection technique, which is based on symmetrical component approach. Using this protection technique, it is possible to detect minor turn-to-turn faults in power transformers. This protection technique is being studied via an extensive simulation study using MATLAB/SIMULINK software in three phase power system. The new protection principle is based on the theory of symmetrical components, or more exactly, on the negative sequence currents. To have accurate feature extraction and to improve the sensitivity of proposed technique, wavelet transform (WT) has been employed. In this paper a multi winding transformer of 100 MVA, 138/13.8 KV, Y-Y is simulated using MATLAB software. Different percentages of inter turns of power transformer are short circuited and it is observed that the changes in transformer terminals current is very small. To observe significant changes, negative sequence currents are extracted using symmetrical component approach. The phase angle shift on both sides of the transformer during incipient faults is found to be significant. However, to improve the sensitivity of the proposed technique, wavelet has been employed. Using the wavelet “db3” at level4 the phase angle variations of negative sequence currents during fault incidence period are analyzed. The absolute peak values of detailed1 coefficients on primary and secondary sides are calculated. The ratio of absolute peaks on faulted side to that of non-faulted side is used for feature extraction.