Insulation Materials Test and Electric Field Analysis for 330 kV IOCT used in Traction Network

The Study of VFTO Distribution in the Insulation System of IOCT Used in Traction Network

“…The total distributed capacitance K and resistance R are obtained by the method mentioned in the previous section, and they are both functions of water content m% and frequency ω. The ground capacitance C is obtained by the mirror image method, and the single-layer insulation voltage equation can be established, as shown in the following Equation (7):…”

“…Whether the calculation of the equivalent network parameters is correct or not has a great influence on the calculation accuracy of the electric field. To analyze the overvoltage transient of transformer insulation, in the frequency range of 10 MHz, it is necessary to consider the frequency and humiditydependent characteristics of the parameters, especially the influence of relative permittivity and conductivity, with frequency and humidity on VFTO [7]. The significance of water content is paramount: a humidity of 4% can shorten a transformer's operational lifetime by a factor of 40 (i.e., by 97.5%), while oxygen only reduces it to one-half [8].…”