... building,airport,station,wharf,enterprise,tunnel,etc.It is mainly used in power supply occasions of AC 50-60HZ and voltage less ... gas,steam,chemical deposition,dust or dirt that will affect transformers insulation seriously,also explosive or corrosive medium is not allowed ... airport, station, wharf, enterprise, tunnel, etc. It is mainly used in power supply occasions of AC 50~60Hz and voltage less than ...