What Are The Effects Of The Imbalance Of The Three-phase Current Of The Diesel Generator Stator?

Diesel generators are designed for long-term operation when the three-phase currents are symmetrical. When the three-phase currents are symmetrical, the stator rotating magnetic field generated by them rotates in the same direction and the same speed as the rotor. Therefore, the stator rotating magnetic field and the rotor rotating magnetic field are opposite. At rest, its magnetic field lines will not cut the rotor. When the three-phase current is asymmetric, it will generate a negative sequence current. The magnetic field generated by the negative sequence current makes the surface of the rotor generate twice the power frequency, which is 100 cycles/sec. Current, this current can cause the rotor to generate heat and vibrate. The main reasons for the imbalance of the stator’s three-phase current are as follows.

　　① The stator phase of the generator is open. At this time, the stator current of the generator phase is 0 and the other two phases increase or equal. The three-phase current phenomenon of other generators running in parallel is the opposite.

　　②When one phase of the low-voltage side of the main transformer is disconnected, the three-phase current of the generator will increase and equal in two phases, and one phase will decrease or be zero.

　　③When the main transformer is high, the medium voltage side or one phase of the line is open, the generator stator three-phase current increases in one phase, and decreases in two phases.

　　④ Caused by the unbalanced external load of the tie line or line.

When the above situation occurs, the treatment method is as follows:

　　① When the three-phase current is found to be unsymmetrical, judge whether it is a fault in the measurement circuit or a fault in the primary circuit.

　　② If one phase of the generator is disconnected, disconnect the generator.

　　③ If the main transformer coil is broken, the faulty main transformer can be stopped.

　　④ If the generator stator current unbalance exceeds the regulation due to line disconnection or load imbalance, it can be judged according to the line three-phase ammeter and the line will be shut down.