Line Entrance Protection of 500 KV Gas Insulated Substations by SF6 Spark Gaps

The use of both station arresters and line entrance arresters provides absolute protection for all operating conditions of gas insulated substations (GIS). However, it represents a costly installation. Hence the adoption of line entrance rod gaps in air can be taken into consideration. But their protection ability is questionable because the slope of the V-t curves for air gaps is much steeper than that for GIS, while SF6 spark gaps with good sparkover characteristics would meet the requirements for the ability to protect the line entrance apparatus of GIS.