1. The generator is overheated

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; the frequency will be too low, which will slow down the cooling fan speed and affect the heat dissipation of the generator; The power factor is too low, which will increase the rotor excitation current and cause the rotor to heat up. Check whether the instructions of the monitoring instrument are normal. If not, necessary adjustments and processing 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 three-phase current imbalance. The imbalance of three-phase currents will produce a negative-sequence magnetic field, which will increase losses and cause heating of 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.

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. Add too much or too little grease to the bearings. Lubricating grease should be added as specified, 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 is advisable not to 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, it may cause friction between the stator and the rotor, causing local overheating of the stator and the rotor. The bearings should be checked for noise. If friction between the stator and rotor is found, the bearings should be repaired or replaced.

7. The insulation of the stator core is damaged, causing short circuits between the chips, causing increased eddy current loss and heating in local parts of the core. In serious cases, the stator windings may be damaged, and maintenance should be carried out.

8. The parallel wires of the stator winding are broken, which increases the current of other wires and heats up. Maintenance should be carried out.

2. There is abnormal voltage on the neutral line of the generator to the ground

1. Under normal circumstances, due to the influence of higher harmonics or manufacturing processes, the air gap under each magnetic pole is uneven and the magnetic potential is unequal, resulting in a very low voltage. If the voltage is one to a few volts, there is no danger and there is no need to deal with it.

2. Short-circuiting or poor insulation to the ground in the generator windings will cause damage to the electrical equipment and generator performance and be prone to heat. 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. Excessive generator current

1. If the load is too large, the load should be reduced.

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

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

5. Stator winding insulation breakdown and short circuit

1. The stator windings are damp. For generators that have been suspended for a long time or have not been repaired for a long time, the insulation resistance should be measured before being put into operation, and those that fail to pass are not allowed to be put into operation. The damp generator must be dried.

2. Defects in the winding itself or improper maintenance process may cause insulation breakdown or mechanical damage to the winding. Insulation materials should be selected according to the specified insulation grade, and winding embedding and lacquer drying should be carried out strictly in accordance with process requirements.

3. The windings are overheated. Overheating of windings will reduce insulation performance, and sometimes insulation breakdown will be quickly caused at high temperatures. Inspection should be strengthened to prevent overheating of various parts of the generator and damage to winding insulation.

4. Insulation aging. When a general generator is operated for 15 to 20 years, its winding insulation will age, its electrical properties will deteriorate, and even the insulation will break down. The maintenance and preventive work of the generator must be done well. If the insulation is found to be substandard, the defective windings should be replaced in time to extend the service life of the generator.

5. Metal foreign matter entered the inside of the generator. Do not leave metal objects, parts or tools in the stator bore after repairing the generator; tighten the binding wires of the rotor and tighten the end parts to avoid loosening due to centrifugal force.

6. Loose stator core

Due to improper manufacturing and assembly, the iron core is not tightened properly. If the entire iron core is loose, two iron plates smaller than the inner diameter of the end of the stator winding can be used to tighten the iron core. After restoring the original shape, tighten the original clamping bolts of the iron core. If the local iron core is loose, you can first apply silicon steel sheet paint between the loose sheets, and then insert hard insulating material into the loose part.

7. Short circuit between iron chips

1. The iron chip is loose, and when the generator is running, the iron core will vibrate and damage the insulation; the insulation in some places of the iron chip will be damaged or the iron core will be partially overheated, causing the insulation to age, and it should be replaced in time.

2. The edge of the iron chip has burrs or is mechanically damaged during maintenance. Use a fine file to remove burrs, trim the damage, clean the surface, and apply a layer of silicon steel sheet paint.

3. If solder or copper grains are shorted to the core, the metal welding joints should be scraped or chiseled and the surface should be treated well.

4. Arc short circuit in the winding may also cause a short circuit in the iron core. The burned part should be removed with a chisel and the surface should be treated well.