1. The generator does
not operate according to the specified technical conditions. For example, if
the stator voltage is too high, the iron loss increases; if the load current is
too large, the stator winding copper loss increases.
If the frequency is too
low, the cooling fan speed will be slowed down, which will affect the heat
dissipation of the generator. If the power factor is too low, the rotor
excitation current will increase and the rotor will heat up. Check that the
indication of the monitoring instrument is normal. If it is abnormal, necessary
adjustment and treatment shall be carried out to make the generator run 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 current exceeds 10% of
the rated current, it is a serious phase current imbalance, and the three-phase
current imbalance will generate a negative sequence magnetic field , increasing
the loss, causing magnetic pole winding and ferrule and other components to
heat up. The three-phase load should be adjusted to keep the current of each
phase as balanced as possible.
3. The air duct is
blocked by dust accumulation, resulting in poor ventilation, which makes it
difficult for the generator to dissipate heat. The dust and oil dirt on the air
duct should be removed to make the air duct unobstructed.
4. If the air inlet
temperature is too high or the water inlet temperature is too high, the cooler
may be blocked. Reduce the air or water inlet temperature to clear the blockage
in the cooler. Before the fault is eliminated, the generator load should be
limited to reduce the generator temperature.
5. Too much or too
little grease is added to the bearing. it should be added according to the
regulations, usually 1/2 to 1/3 of the bearing chamber (the upper limit for low
speed and the lower limit for high speed), and not more than 70% of the bearing
chamber is appropriate.
6. The bearing is worn.
If the wear is not serious, the bearing will overheat locally; if the wear is
severe, the stator and rotor may be rubbed, causing the stator and rotor wall
to overheat. The bearing should be checked for noise. If friction between the
stator and rotor is found, stop the machine immediately for maintenance or
replace the bearing.
7. The insulation of the
stator core is damaged, causing a short circuit between the pieces, which
causes local eddy current loss of the core to increase and generate heat, and
in severe cases, the stator windings are damaged. Stop the machine immediately
for maintenance.
8. The parallel wires of
the stator winding are broken, causing the current of other wires to increase
and heat up. Stop the generator immediately for maintenance.
Generator
neutral line has abnormal voltage to the ground
1. Under normal
circumstances, very low voltage appear due to the influence of high harmonics
or manufacturing process, the air gap and magnetic potential is uneven. If the
voltage is between one and several volts, there is no danger, do not need to
deal with .
2. The generator winding
has a short circuit or poor insulation to the ground, which causes the
performance of the electrical equipment and generator to deteriorate, and it is
easy to heat up. It should be repaired in time to avoid the expansion of the
accident.
3. The neutral line has
no voltage to ground when no load, and the voltage appears when there is a
load, which is caused by three-phase imbalance. The three-phase load should be
adjusted to make it basically balanced.
Excessive
generator current
1. The load is too
large, and the load should be reduced.
2. If a short circuit or
ground fault occurs on the power transmission line, the line should be repaired
and returned to normal after troubleshooting.
Generator
terminal voltage is too high
1. The grid voltage of
the generator parallel to the grid is too high. The voltage of the parallel
generator should be reduced.
2. The overexcitation
caused by the failure of the excitation device, the excitation device should be
repaired in time.
Generator
loses remanence and cannot generate power when starting
1. Residual magnetism is
often lost after shutdown because the material used for the exciter magnetic
pole is close to soft steel, and the remanence is less. When there is no
current in the excitation winding after shutdown, the magnetic field disappears.
A storage battery should be prepared and magnetized before generating
electricity.
2. The magnetic pole of
the AC generator loses its magnetism, and the DC current larger than the rated
current (with a very short time) should be passed through the winding for
magnetization, that is, sufficient residual magnetism can be restored.
Excitation
reactor temperature of automatic excitation device is too high
1. The reactor coil is
locally shorted, and the reactor should be repaired.
2. The air gap of the
magnetic circuit of the reactor is too large. The air gap of the magnetic
circuit should be adjusted.
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