How to deal with sudden short circuit of diesel generator set?
Characteristics of sudden short circuit
1. In steady state short circuit, the synchronous reactance is large. Therefore, its steady-state short-circuit current is not large, but when it is suddenly short-circuit. Because of the very small transient reactance which limits its current. It also contains DC component. Therefore, the sudden short circuit current is very large. Its peak value can reach more than ten times of the rated current.
2. With the appearance of this impulse current. The winding of the motor will be subjected to a great impact electromagnetic force. It may deform the winding and even damage the insulation of the winding.
3. In the process of sudden short circuit, the motor may vibrate due to the strong short-circuit torque.
4. The stator and rotor windings of the motor have overvoltage.
Characteristics of internal physical phenomena of generator under sudden short circuit.
1. The armature current is constant in steady state short circuit. The corresponding armature magnetomotive force is a constant amplitude rotating magnetic field rotating at synchronous speed. As a result, no electromotive force is induced in the rotor winding and current is generated. From the current relationship, it is equivalent to the open circuit state of the transformer.
2. In case of sudden short circuit, the magnitude of armature current varies. The amplitude of the corresponding armature magnetic field is variable, so the transformer acts between the stator and the rotor. The induction potential and current in the rotor winding will affect the current change in the stator winding. From the electromagnetic relationship, it is equivalent to the sudden short circuit state of the transformer.