Modeling of high frequency characteristic of a 6.6 kV transformer

In this paper, a high frequency characteristic of a 6.6 kV transformer winding with a continuous disc type high voltage (HV) winding which consists of 13 turn and 22 discs is modeled. The formulation of the distributed parameters particularly the capacitances are determined according to the geometry and construction of the HV winding of the transformer. The determination of turn-to-turn and coil-to-coil capacitances of the winding is also taken into consideration. In addition, the model also includes the total value of series capacitance, Cs for the unshielded winding, the total ground capacitance, Cg, the series resistance, Rs and resistance to ground, Rg. The accuracy of the developed high frequency transformer model is simulated by using a computer simulation package, PSCAD and compared with the measurement results. A low voltage impulse with a double-exponential waveform which is similar to the characteristic of a lightning impulse is employed for the performance study of the developed model. The results obtained from both the simulation and the measurement are in good agreement.