1. Introduction JN15 12 kv series indoor high voltage earthing switch is a compositional type, and the technical parameters is corresponding to the requirements of IEC62271-102:2002. It is applicable for three-phase power system of 3-12kv, AC 50HZ. It can be used together with many types high voltage switchgear as a earthing protection unit. 2. Applicable environment 2.1 Altitude should not exceed 1000 m 2.2 The ambient temperature: -25?~ +40? 2.3 The seismic intensity should not exceed 8 degree. 2.4 Relative humidity should not exceed 95%, monthly average value should not exceed 90%. 2.5 Pollution degree: ? Main technical parameters Rated voltage: 12 kv Rated short-time withstand current: 31.5 KA Rated short-circuit duration time: 4 s Rated making current: 80KA Rated withstand current(peak value): 80KA Pole to pole distance: 150 mm, 210 mm, 230 mm, 250 mm, 275 mm Power frequency withstand voltage(1 minute) To earth, phase to phase: 42 kv, 48 kv