Experimental Study on Single-Phase Grounding Fault Safety Current of Large Generators

Single phase grounding fault is one of the most common faults of large generator stator winding insulation breakdown and the fault current will endanger the safety of the stator core. However, there is no consensus on the safety current between different working groups. This paper provides an experimental way to study the influence of grounding fault current and fault duration on the stator core, more than 300 experiments have been carried out. The discharge voltage, current, dissipated power and damage of the stator core in the experiment are measured and analyzed, the relationship between them are given. Also an arc model is introduced to reveal the discharge process between the stator winding and the stator core. A safety current is proposed and the experiment results can be used for the selection of the neutral grounding mode of large generators in order to protect the stator core.