Risk of burn-through-a quantitative assessment of the capability of gas-insulated equipment to withstand internal arcs

The author introduces the notion of the risk of burn-through, borrowed from the risk of failure widely used in the statistical approach to insulation coordination, to evaluate the capability of gas-insulated equipment and substations (GIS) to withstand burn-through due to internal arcs. A sensitivity analysis performed to identify the main parameters affecting the risk of burn-through showed that the risk increases with the mean fault current. Both the fault-clearing characteristics of the switching apparatus and the GIS design, namely the envelope thickness and the GIS section length between two consecutive insulators, were found to have a significant influence on the risk of burn-through. To keep the risk of burn-through reasonably low, appropriate coordination must be made among the fault-clearing characteristics of the switching apparatus, the GIS design, and the distribution of the local fault currents