Curve of limiting parameters in risk analysis of MV overhead line outages
Abstract
This paper studies risk of outages on medium voltage (MV) overhead distribution lines due to flashovers from nearby indirect lightning strikes. Probability of this type of flashover on the line insulation depends, apart from the strike distance itself, on the amplitude and wave-front time of the lightning current. Only downward negative lightning is considered, where all related parameters have stochastic nature. The paper will develop a relationship between the so-called critical lightning-current amplitude for the flashover onset and the associated distance of the strike location from the line. By linking together these critical amplitudes, for different distances, a so-called curve of limiting parameters of the line, in relation to indirect strikes, is obtained. This curve further gives rise to the risk of flashovers on MV distribution lines due to nearby indirect lightning strikes. The risk can then be employed for estimating economic viability of different measures for reducing outages, as well as for the statistical insulation coordination of the line.
