Abstract
Monitoring of winding faults is the most important item used to determine the maintenance status of a transformer. Commonly used methods for winding-fault diagnosis require the transformer to exit operation before testing and an external exciting signal, whether the transformer is malfunctioning or not. However, if an overvoltage signal can be regarded as a broadband excitation source for fault diagnosis, then the interference caused by signal injection can be eliminated without the need for additional pulse or impulse signals. In this paper, a tapped transformer is designed and test platforms are built to compare winding diagnoses using the impulse wave and sweep frequency response analysis methods by recording voltage responses on both the high- and low-voltage sides and calculating the respective transfer functions. Based on comparison of statistical indicators, it is found that the sensitivities of both methods are similar for detecting conditions of winding-ground and winding-interlayer short circuits. It is concluded that it is feasible to use a transient overvoltage monitoring system for winding-fault diagnosis.
Highlights
Power transformers are recognized as one of the most important transmission components in the operation of the power system
For the |U| of parts of the curves greater than 0, as the tests proceed under high voltage conditions, the wave interference caused by reflection and refraction of the impulse waves, which was applied at HV, may cause the voltage obtained at LV to be higher than that at HV
This may be avoided if the impulse wave method could be applied to diagnose diagnose the winding fault and the overvoltage monitoring system is applied to the transformer
Summary
Power transformers are recognized as one of the most important transmission components in the operation of the power system. Unlike SFRA and IFRA, the voltage level of such transient overvoltage signals applied to a transformer can be of the order of kilovolts; the impulse wave method was selected for the experimental testwork. The impulse wave method uses a transient overvoltage signal, which can be obtained by sensors of the overvoltage monitoring system as the exciting signal to diagnose the transformer winding faults, and has the potential for online application. For the transformer winding faults conditions are calculated and analyzed using statistical indicators to describe the used in these experiments, it is found that the sensitivity of the impulse wave method is similar that differences between two curves. The results that the under sensitivity of theofimpulse wave method is similar to that short-circuit of SFRA under conditions of demonstrate that the impulse wave method could be feasible for online diagnosis of transformer winding-ground and winding-interlayer short-circuit faults.
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