Measurement of neutral currents in a power transformer and fault detection using wavelet techniques

Fault analysis and diagnosis of a transformer are essential, as power quality is one of the primary concerns of the electric power utilities. Insulation failure within transformer windings is considered to be one of the most important causes of the failure of power transformers. A comparison of neutral currents at reduced and full voltages is carried out for detection of faults in a power transformer winding during impulse tests. If the fault is of a minor nature viz., inter-turn, the neutral current comparison may not reveal the failure. To detect such minor faults, a new technique based on wavelets has been employed. Experimentally obtained neutral currents, analyzed using the Morlet wavelet, are discussed in this paper.