Rotor turn-to-turn short circuit is one of the common faults of hydro-generators, which is extremely harmful to the safe operation of generators. Turn-to-turn short circuit can be divided into two situations: one is that the generator has just been put into operation, and the generator has turn-to-turn short circuit under no load or light load. The phenomenon is that the machine pit smokes and the insulation is burnt. The other is the turn-to-turn short circuit of the generator after long-term operation, which is caused by many reasons, such as poor manufacturing process, poor operation and maintenance, metal chips or dust falling on the stator winding, which is not cleaned for a long time to form turn-to-turn short circuit, or it may be that small animals such as mice climb into the stator hole to cause turn-to-turn short circuit.

In the first case, when turn-to-turn short circuit occurs, the stator voltage and current do not change obviously due to light load or no load (the power supply voltage is normal), but the machine pit smells of smoke and insulation burning. The personnel on duty should check whether there is smoke, peculiar smell and abnormal sound in the generator pit according to the load of the generator. When measuring and checking the generator with voltage transformer, current transformer and instrument, the generator differential protection is applied to eliminate the fault. When conditions permit, two-in-one (overcurrent, low voltage and overvoltage) protection is also adopted to eliminate faults. When the conditions are not met, the fault can be removed through the backup protection of the generator.

In the second case, when the turn-to-turn short circuit occurs, the load is heavy or full. The stator voltage and current will change obviously. The stator current increases and the voltage decreases. At this time, the generator load should be reduced immediately, and the shift supervisor and the leader of electric branch should be reported quickly. Ask the chief engineer, the biotechnology department and the leaders of the operation department to turn off the excitation switch and stop the generator. When conditions permit, external inspection and measurement should be carried out as far as possible to accurately locate the fault point. For example, measure the current value and voltage change of turn-to-turn short circuit, and measure the unbalanced magnetic pull. When it is determined that the generator can continue to run, it should be reported to the leader for approval and run in parallel. When the conditions are not met, the fault should be removed by the backup protection of the generator.