Volt-Time Curve Prediction of Distribution Insulators Under Standard and Typical Lightning Overvoltages Using the Disruptive Effect Method

Through the development of detection and measurement systems for lightning strokes, the possibility arose for the identification of the characteristic parameters of lightning current and the resulting voltage waveforms that stress the power system insulating equipment. The real lightning voltages that stress the insulation may vary over a wide type of waveforms and may also differ significantly from the standard 1.2/50 mu s lightning impulse voltage. Therefore, the prediction of volt-time characteristics of any insulating material for such non-standard voltages is required for a proper insulation design. In this regard, this paper aims at evaluating the dielectric behaviour of medium voltage insulators subjected to voltage impulses with standard and non-standard waveforms, by applying the disruptive effect method. The non-standard lightning overvoltage waveforms considered in this study were based on lightning overvoltages produced by real return stroke current waveforms observed on conveyed measurement data. The investigation involves a comparison between measured and predicted voltage-time characteristics of insulators, considering single-peaked and double-peaked non-standard impulsive voltage waveforms as well as the standard lightning impulse voltage. Three different types of insulating arrangement involving 15- and 25-kV pin-type porcelain insulators were investigated. The estimation of the parameters required for this prediction method was performed using a simulation language available at ATP/ATPDraw software called MODELS.