Surge voltage performance of power transformer winding sections provided with metal oxide surge absorber blocks with faults in portion of sections

Abstract

Recent investigations by few researchers have shown that transient voltage distribution across winding sections of power transformer can be controlled by providing suitable metal oxide surge absorber (MOA) blocks across these sections. However, it is to be ascertained that in the event of occurrence of faults in such type of transformer winding sections whether it is possible to identify the fault. The present investigations have been aimed to analyze and identify the parameters that may change as a result of occurrence of fault in sections of transformer winding even though these sections are provided with MOA protection blocks. High voltage windings with 'alpha' values in range of 6 to 18 have been analyzed by carrying out simulations using PSPICE software. These investigations have shown that there is no appreciable change in voltage waveforms even when faults to the extent of 5% of winding length occur in any of the winding sections. Further investigations have indicated that there are changes in waveform of current flowing through transformer winding neutral line when 5% of total winding length faults are present in any one section. These changes are not large in magnitude and are observed to occur at 50 microsecond or 100 microsecond instants on the neutral current waveform. Depending on the value of alpha, the change in magnitude of neutral currents are found to be in the range of 3% to 9% at either of 50 microsecond or 100 microsecond time instant.