1 Overview 
Breaker, disconnector, grounding switch, built-in current transformer and incoming and outcoming bushing such as combination of grounding are put in metal shell, filling certain pressure SF6 gases as insulating medium composed of complete sets of equipment, which applies to AC three-poles 50Hz, rated voltage 72.5~126KV power supply system. 
The ZHW meets international standards GB7674--1997 and IEC 60517. 
2 Service and Installation Conditions 
Installation place: Outdoor/indoor 
Air temperature: -40~+40 
Elevation: ≤ 1000m(No limitation for special order) 
Daily range of temperature: 25 
Relative humidity (RH): Daily average: ≤ 95%, monthly average: ≤ 90%(25) 
Wind speed: ≤ 35m/s(wind presssure ≤ 700PA) 
Irradiance: ≤ 0.1W/cm(wind speed: 0.5m/s) 
Thickness over ice: ≤ 10mm 
Creepage distance: 31mm/kv

http://www.villeelectric.com/gas-insulation-switchgear/4278070.htmlhttp://www.villeelectric.com/products.html