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Use of frequency response analysis to detect transformer winding movement

Ahmed, Ibrahim (2013) Use of frequency response analysis to detect transformer winding movement. Other thesis, Murdoch University.

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In this thesis, a study of continuous disc type 6.6kV transformer winding was utilised to investigate winding deformation by means of frequency response analysis (FRA). The equivalent electrical circuit is based on the lumped parameter model. Transformer elements include series capacitance, ground capacitance and inductance. The calculation were based on 6.6kV transformer design specification data sheet.

The values of the parameters were changed in order to simulate a likelihood of failure on the windings, which would correspond to unique frequency range spectrum. The FRA simulation range is from 10 kHz to 2 MHz. Then sensitivity analyses were performed to assess the accuracies of the two types of measurand: transfer function (Vout/Vin ) and trans impedance ( Vin/Iout).

Matlab/simpowersystem software was used for simulation analysis and the bodeplot command was implemented to graph the magnitude and phase of the equivalent circuit (healthy circuit) and circuit with introduced fault. A linear frequency scale was utilised in order to compare the small differences at certain frequency bands. This thesis presents FRA which includes sweep frequency response analysis (SFRA), the measurement techniques and interpretation of SFRA measurement.

In this thesis, a simulation model of a continuous disc type 6.6kV transformer was utilised to study frequency response analysis (FRA) which includes SFRA. The model was based on lumped parameters using circuit elements of series capacitance, inductance and ground capacitance. Faults were simulated through change in value of series capacitance, inductance and ground capacitance. . It was found that an increase of 20% in inductance, which corresponds to disc deformation and local breakdown faults etc. alters the FRA signature over the entire frequency range (10 Hz-2 MHz). On the other hand a change in series capacitance and ground capacitance which correlates to disc movement faults occurs only at frequencies above 400 kHz.

Publication Type: Thesis (Other)
Murdoch Affiliation: School of Engineering and Information Technology
Supervisor: Hettiwatte, Sujeewa
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