What are the fault diagnosis and troubleshooting methods for diesel generator sets:

 1. Generator overheats

 (1)The generator does not operate according to the specified technical conditions, such as the stator voltage is too high, the iron loss will increase; the load current will increase, the copper loss of the stator windings will increase;

 If the frequency is too low, the speed of the cooling fan will slow down and affect the heat dissipation of the generator; if the power factor is too low, the rotor excitation current will increase, causing the rotor to heat up. Check whether the instructions of the monitoring instrument are normal. If it is abnormal, necessary adjustments and treatments must be carried out to make the generator operate in accordance with the specified technical conditions.

 (2)The three-phase load current of the generator is unbalanced, and the overloaded one-phase winding will overheat;

 If the difference between the three-phase currents exceeds 10% of the rated current, it is a serious phase current imbalance. The three-phase current imbalance will generate a negative-sequence magnetic field, thereby increasing losses and causing heating of magnetic pole windings, ferrules and other components. The three-phase load should be adjusted to keep the current of each phase balanced as much as possible.

 (3)The air duct is blocked by accumulated dust and poor ventilation, making it difficult for the generator to dissipate heat. Dust and oil scale accumulated in the air duct should be removed to make the air duct smooth and unobstructed.

 (4)The inlet air temperature is too high or the inlet water temperature is too high, and the cooler is blocked. The inlet air or inlet water temperature should be reduced to remove blockages in the cooler. Before the fault is eliminated, the generator load should be limited to reduce the generator temperature.

 (5)If you add too much or too little grease to the bearing, you should add grease according to regulations, usually 1/2 to 1/3 of the bearing chamber (the upper limit is taken for low speed, and the lower limit is taken for high speed), and it should not exceed 70% of the bearing chamber.

 (6)Bearing wear. If the wear is not serious, the bearing will be locally overheated; if the wear is serious, the stator and rotor may rub, causing the stator and rotor to overheat. The bearings should be checked for noise. If friction between the stator and rotor is found, the bearings should be stopped immediately for maintenance or replacement.

 (7)The insulation of the stator core is damaged, causing short circuits between the chips, causing increased eddy current losses in local parts of the core and heating. In serious cases, the stator windings may be damaged. Shut down immediately for maintenance.

 (8)The parallel wires of the stator winding are broken, causing the current in other wires to increase and generate heat. Shut down immediately for maintenance.

 2. There is abnormal voltage between the generator neutral line and the ground

 (1)Under normal circumstances, a very low voltage due to uneven air gaps and uneven magnetic potential under each magnetic pole due to the influence of higher harmonics or manufacturing processes. If the voltage is between one to several volts, it will not be dangerous and does not need to be dealt with.

 (2)Short circuits in the generator windings or poor insulation to the ground will cause the performance of electrical equipment and generators to deteriorate and cause heat to occur. Maintenance should be carried out in time to avoid the expansion of the accident.

 (3)There is no voltage on the neutral line to the ground when there is no load, but the voltage appears when there is a load. It is caused by the imbalance of the three phases. The three-phase load should be adjusted to make it basically balanced.

 3. The generator current is too large

 (1)If the load is too large, the load should be.

 (2)If an inter-phase short circuit or a ground fault occurs on the transmission line, the line should be repaired and it can return to normal after the fault is eliminated.

 4. The generator terminal voltage is too high

 (1)The voltage of the generator parallel to the power grid is too high, and the voltage of the generator parallel should be reduced.

 (2)If the fault of the excitation device causes over-excitation, the excitation device should be repaired in time.