Analysis and Diagnosis of Ground Fault and Inter-turn Short Circuit of Rotor Winding in 600MW Turbo-generator
Jiang Jianmin · Large Electric Machine and Hydraulic Turbine · 2015
This paper introduces a kind of rotor winding grounding fault locating method. When the rotor winding of turbo-generator has grounding fault, a large current method can be used for diagnosis and it can find the grounding position roughly. But the large current method need a large capacity power supply and has the risk of damaging rotor. For hydrogen-cooled rotor of turbo-generator, to locate the axial and circumferential earthing position, a method that applied DC voltage on rotor winding poles and measured the ground potential by vent hole can be used instead of large current method. The magnetic pole-to-pole short-circuit of rotor winding was caused by foreign metal bodies in a power plant 600 MW turbo-generator, then developed the grounding fault,caused serious damage on retaining rings of generator rotor. When severe short-circuit fault as magnetic pole-to-pole short-circuit occurred, the rotor parts was easy to burn because of the large short circuit current, even caused the grounding faults. When both inter-turn short circuit and grounding fault happened simultaneously,the generator should be stopped immediately. Therefore,in order to prevent the accident, the possibility of the rotor one point grounding fault protection acting on the trip should be researched when both rotor windings inter-turn short circuit and grounding fault happened simultaneously.