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Description
The Voltage Holding Prediction Model (VHPM) is a design technique formulated at Consorzio RFX that combines numerical modelling and experimental data in order to calculate a breakdown probability curve. The cuve is based on the two parameters Weibull distribution for any multi-electrode multi-voltage vacuum insulated system under dc voltage. The progresses in employing the VHPM to predict the Lightning Impulse Voltage Waveform (LIVW) breakdown probability of medium voltage Vacuum Interrupter (VI) are the subject of the present contribution. A new experimental campaign on two Siemens VI models have been carried out at the high voltage laboratory of the Industrial Engineering Department of the Padua University. The use of a convenient methodology of experimental data acctual, called Always Breakdown method, allowed to improve the quality of the data obtaining a well fitted Weibull distribution of the voltage breakdown. This topic is described in detail in another contribution.
The analysis of the two different VI models, with different key features, allowed a better understanding of the ability of the VHPM to describe different physical arrangements and explain the resulting breakdown behavior. This contribution describes the analyses carried out on the two models, in different conditions such as electrodes gap, polarity and maximum applied LIVW voltage, with the Weibull shape and scale parameters (m and W0) calculated by fitting the experimental data for the two tube models, in order to assess the prediction capability of the proposed method.
Reason of measurement-prediction discrepancy is supposed to be sought in an arc onset-peak voltage delay time affecting the correct interpretation of the experimental measurements used to estimate m and W0. Preliminary analysis on this specific topic, as well as an assessment of the influence of the parameters adopted in the physical model are also described.
