In this paper

the internal fault of current transformer due to insulation damage of zero-screen lead is analyzed.The fault shows the dissolving gas in the insulation oil exceeds severely the limit

with total hydrocarbon up to 3 668μL/L

acetylene up to 2 227μL/L and fault code is 102.It is thought by judgment that the low energy discharge and concurrently overheat are discharge fault are existed inside the equipment.The equipment

before being returned to the manufacture for disassembly

is subject to such test of dielectric loss factor

capacitance and PD

of which the result shows normally except the capacity is slightly exceeded.It is found after disassembly that the roof of zero-screen lead has broken and the corresponding conductive rod of primary winding has remarkable galvanic corrosion trace and carbon black deposition is existed.It is though through comprehensive analysis that the fault is due to insulation damage at the roof of zero-screen lead

developing initially from low energy spark discharge gradually to arc discharge

the multi-contact conduction at the breakage of zero-screen causes excessive heat of loop current

thus causing the dissolving gas in the oil excess severely the limit.