... during shipping and sustained operation7.Security: pressure relief valve, signal thermometer, gas relay8.Corrosion resisting treatment, maintenance free S9-M-630 ... Distribution TransformerPrimary voltage: 6, 6.3, 10, 10.5, 11,35kV,Tapping range: ±5%Secondary voltage: 3, 3.15, 6.3kVConnection group ...