The dependence of the expectable number of transmission line faults on the degree of the compactness

Nowadays environmental aspects play a determining role in overhead line designing. The compaction of the transmission lines means a reduction of the dimensions of the towers and the length of the insulators, so the lightning and switching withstand voltage of the insulator configuration of a compact line can be lower, than that of a conventional line. The behaviour of the insulators stressed by standard waves is known usually. On the other hand, the voltage stress of the insulators differs from the standard 1.2/50 μs waveform considering a real line, because of the reflections on the grounding, on the neighbouring towers etc. In the paper simulation results will be published, taking into account also the difference between the real wave shapes and the standard one. To obtain such results, the calculation of the disruptive effect (DE) has been implemented to estimate the withstand of the insulators to nonstandard voltage stress and on the other hand to determine the probability of a back-flashover initiated by lightning strokes. To find the optimal number and location of line arresters or find an other way to reduce the number of back-flashover a detailed analysis of the processes initiated by lightning strokes is required.