1. Generator overheating
(1) The generator does not
operate in accordance with the specified technical conditions, such as too high
stator voltage, iron loss increases; if the load current is too large, the
copper loss of the stator winding increases; if the frequency is too low, the
cooling fan speed becomes slow, affecting the heat dissipation of generator;
the power factor is too low, so that the rotor excitation current increases,
resulting in the rotor heating. Check whether the indication of monitoring
instrument is normal. If it is abnormal, necessary adjustment and treatment
must be carried out to operate the generator in accordance with the specified
technical conditions.
2. The generator neutral line has
abnormal voltage to the ground.
(1) Under normal circumstances,
due to the influence of high harmonics or manufacturing process, the air gap
under each magnetic pole is uneven and the magnetic potential is unequal, and
the voltage is low. If the voltage is in the range of one to several volts,
there will be no danger, do not have to deal with.
(2) The generator winding has
short circuit or poor insulation to the ground, which leads to the
deterioration of electrical equipment and generator performance, easy to heat.
It should be repaired in time to avoid accidents.
(3) Neutral line has no voltage
to ground at no load, and voltage occurs when there is load. It is caused by
three-phase unbalance, and the three-phase load should be adjusted to make it
basically balanced.
3. Generator current is too
large.
(1) If the load is too large, the
load should be reduced.
(2) If the transmission line has
short circuit or grounding fault, the line should be overhauled and restored to
normal after troubleshooting.
4. The generator terminal voltage
is too high.
(1) If the grid voltage of
generator parallel to the power grid is too high, and the voltage of parallel generator should
be reduced.
(2) If the fault of excitation
device causes overexcitation, the excitation device should be repaired in time.
5. Insufficient power
Since the voltage source compound
excitation compensation of the excitation device is insufficient, the
excitation current required for the armature reaction cannot be provided, so
that the generator terminal voltage is lower than the grid voltage and the
rated reactive power cannot be delivered. The following measures should be
taken:
(1) A three-phase voltage
regulator is connected between the generator and the excitation reactor to
increase the terminal voltage of the generator, so that the magnetic potential
of the excitation device is gradually increased.
(2) Change the phase between the
voltage magnetic-flux potential of the excitation device and the terminal
voltage of the generator to increase the total magnetomotive force. Several
thousand ohms and 10W resistors can be connected in parallel at both ends of each phase winding of the
reactor.
(3) The resistance of the
varistor is reduced to increase the excitation current of the generator.
6. Stator winding insulation
breakdown, short circuit
(1) The stator winding is damped.
For generators that have been stopped for a long time or overhauled for a long
time, the insulation resistance should be measured before putting into
operation. Those who are not qualified are not allowed to put into operation.
The damp generator should be dried.
(2) The winding itself is
defective or improperly repaired, resulting in winding insulation breakdown or
mechanical damage. The insulation material should be selected according to the
specified insulation grade, the embedded winding and the dipping paint should
be strictly carried out in accordance with the technical requirements.
(3) The winding is overheated.
Insulation overheating will reduce insulation performance, and sometimes the
insulation breakdown is quickly caused at a high temperature. Daily inspection
should be strengthened to prevent the generator parts from overheating and damaging the winding
insulation.
(4) Insulation aging. Generally,
generator runs for 15 ~ 20 years, winding insulation aging occurs, electrical
performance changes, and even make insulation breakdown. If the insulation is
found to be unqualified, replace the defective winding insulation in time to
prolong the service life of the generator.
(5) Metal foreign matter enters
the inside of the generator. After repairing the generator, do not leave the
metal objects, parts or tools in the stator; tie the binding wire of the rotor
and fasten the end parts so as not to be loosened by centrifugal force.
7. The stator core is loose.
The core is not fastened due to
improper manufacturing and assembly. If the whole core is loose, for small
generators, two iron plates smaller than the inner diameter of the stator
winding end can be used to tighten the iron core by putting on double head
bolts. After the original shape is restored, the original clamping bolt of the
iron core is tightened. If the local iron core is relaxed, silicon steel sheet
paint can be applied between the slack sheets, and then insert a hard
insulating material into the slack parts.
8. Short circuit between iron
chips
1) The iron core lamination is
slack. When the generator is running, the iron core vibrates to damage the
insulation; if the insulation of the iron chip is damaged or the core is
partially overheated, it will cause insulation aging.
(2) There is a burr on the edge
of the iron chip or mechanical damage during maintenance. Use a fine boring
tool to remove the burrs, repair the damage, clean the surface, and then apply
a layer of silicon steel paint.
(3) If there is solder or copper
particles short iron core, the metal welding joint should be scraped or cut off
to deal with the surface.
(4) The arc short circuit occurs
in the winding, which may also cause the short circuit of the iron core. The
burned part should be removed with a chisel and the surface should be treated.
9. The generator loses remanence
and cannot generate electricity when starting.
(1) Remanence is often lost after
shutdown, because the material used in the magnetic pole of the exciter is
close to the soft steel, and the remanence is less. The magnetic field
disappears when there is no current in the excitation winding after shutdown. A
battery should be provided to magnetize before generating electricity.
(2) The magnetic pole of the
generator loses its magnetism, and a DC current (in a short time) larger than
the rated current should be applied to the winding for magnetization, that is,
sufficient remanence can be restored.
10. Excitation reactor
temperature of automatic excitation device is too high.
(1) The reactor coil is partially
short-circuited, and the reactor should be repaired.
(2) If the air gap of the
magnetic circuit of the reactor is too large, the air gap of the magnetic
circuit should be adjusted.
11. When the generator starts,
the voltage will not rise.
1) The excitation circuit is
disconnected, preventing the voltage from rising. Check whether the excitation
loop is broken and the contact is good.
(2) The residual magnet
disappears. If the exciter voltmeter has no instructions to indicate that the
residual magnet has disappeared, the exciter should be magnetized.
(3) The polarity of the field
coil of the exciter is reversed, and its positive and negative connecting lines
should be swapped.
(4) When performing some tests in
the generator overhaul, the magnetic field coil is mistakenly connected to the
reverse direct current, causing the residual magnet to disappear or reverse,
and the magnetic field should be remagnetized.
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