Ein statistisches Verfahren zur Bestimmung der äußeren lichten Abstände bei Freileitungen

The EN 50341‑1 provides procedures for establishing internal and external clearances for overhead lines. Internal clearances are selected in a way that an acceptable outage performance is achieved, and the external clearances are then coordinated with the internal clearances to ensure that no flashovers occur to objects in the vicinity of the line. In the standard, this coordination is carried out by assuming that lightning overvoltages will be limited by flashovers of the insulator strings. There are, however, cases where this approach may be too conservative, e.g., when long insulators are needed to obtain an acceptable power frequency flashover performance with insulator pollution. In this paper, a method is presented for determining the external clearances on overhead lines based on a statistical evaluation of the representative lightning overvoltage as defined in the EN 50341‑1.