Locating faults in a transformer winding: An experimental study

Based on terminal measurements on a single, continuous-disc winding of a transformer, it is demonstrated how faults introduced at different positions along the winding could be localized with reasonable accuracy. Fault in the present context represents a discrete change, e.g. short-circuiting a few turns within a disc (i.e. predominantly an inductive change) and/or addition of some tens of pico-Farad capacitance between a disc and ground (i.e. predominantly a capacitive change). Open-circuit and short-circuit natural frequencies are determined by sweep frequency measurements, in addition to measuring effective resistance, shunt capacitance and inductance, at the terminals. The proposed method aims at utilizing the measured data to iteratively synthesize a lumped-parameter ladder network, corresponding to each set of measurement. Comparison of such synthesized circuits with a reference (or fault-free) circuit reveals the location, quantum, and nature of fault. Results presented demonstrate the potential of this method.