GENERATOR TREATMENT
Generator
Abnormal operation: generator
cannot operate continuously at rated parameter because of equipment, main
electrical measuring instrument and relay protection exit operation.
a.
overload of generator
1.
The system message for “generator
overload alarm";
2.
The current of stator and rotor exceed
the rated value, the rotor voltage exceed the normal value;
3.
The frequency and voltage of generator
reduce;
4.
active and reactive load exceed normal
value.
1.
over load treatment of generator:
1.
Contact with turbine department to
reduce the inlet air temperature; monitor the generator temperature.
2.
Reduce the exciting current, generator
power factor should be less than specified value, at same time avoid the
generator bus voltage is too low.
If the above methods cannot solve the problem of
overload, should reduce the active load of generator to normal value.
2. treatment of temperature of stator coil and iron core exceed the
specified value:
1.
check whether the generator overload;
2.
contact turbine department to check whether the cooling water
of air cooler is normal;
3.
cooperate with thermal operator to check whether the meters
are normal;
4.
when check and handle the temperature increasing, must reduce
the generator output, ask instructions from shift leader. If the meters and
cooling water are normal, taking measure fails, report to shift leader,
continuous to reduce load until shutdown.
5.
If the temperature of generator coil and iron core increase
rapidly, handling failure and air temperature is abnormal, should request
shutdown as soon as possible.
3.
The phenomenon and hazard of excitation system grounding
connection:
1.
The generator control panel display "excitation loop
earthing" and “two points of rotor loop erating signal device” acts;
2.
rotor current (exciting current) increase violently.
3.
reactive load of generator reduce;
4.
generator vibrates violently;
5.
Voltage of stator and rotor reduce.
Disconnection of
generator PT:
1.
The voltage of disconnection phase reduce or reduce to zero;
2.
value of active and reactive load reduce;
3.
Three-phase stator current, excitation voltage, and current
are in normal condition;
4.
”Microcomputer alarming: "the disconnection of generator
PT".
The disconnection of generator CT:
Phenomenon:
1.
open circuit phase current
reduce, active and reactive indication reduce;
2.
The voltage of generator and
voltage and current are in normal condition.
Cannot increase
voltage of generator: after the generator gets rated speed, according to the
operation procedure, switch on excitation power, no indication or change of
AC/DC meters of generator exciting panel when magnetic increasing and magnetic
reducing.
Treatment:
1.
stop voltage increasing, exit the excitation operation;
2.
check voltage meter, if the excitation rotor loop is
disconnected;
3.
check whether the excitation suppression switch close.
4.
check whether the generator PT and excitation PT are intact;
check whether knife gate close;
5.
check whether the primary insurance of excitation transformer
is intact;
6.
check whether the connection of generator brush is in good
condition.
The treatment for generator accident
Generator nonsynchronous
parallel: when the generator synchronization and main switch on, rotor current
rise suddenly, lead to strong impact, meters of rotor current, voltage, active
power, reactive power vibrate severely, cause the unit vibration.
reasons:
1.
fail to meet the conditions of synchronous parallel;
2.
wrong connection at high voltage side of generator and PT;
3.
synchronous inspection relay or synchronoscope failure;
4.
wrong connection of PT secondary loop or nonsynchronous loop;
5.
Speed governing system of turbine is instable, the operation
of operator is not proper.
treatment:
1.
Disconnect generator switch and excitation suppression
switch; disconnect generator with system and generator shut down.
2.
After unit shutdown, check whether there is deformation of
generator end coil and measure the insulation of stator winding.
3.
Check whether there is damage of main switch; check whether
connection of voltage secondary loop, synchronous device and DC power supply
are correct.
4.
After check, no abnormal or misoperation, report to shift
leader, parallel again.
Loss of synchronization due to generator oscillation:
1.
Rotor current exceed normal
value and current pointer swing strongly;
2.
Motor voltage decrease and
pointer swing strongly;
3.
Pointer of active power and
reactive power meter swing strongly;
4.
Pointer of rotor voltage meter
and current meter swing around normal value;
5.
Rhythmed sound from generator,
the rhythm is in step with the above meters;
6.
The leading phase and phase-lag
swing of power factor and frequency swings.
reasons:
1.
system short circuit, nonsynchronous switch on damage the
stability of system;
2.
cut a large number of load; trip; speed governing of turbine
is instable;
3.
Automatic adjustment excitation device failure.
treatment:
1、 reduce the active
load of generator;
2、 increase excitation
current;
3、 Take the above
measure, if cannot recover in 15 minutes, should request disconnect generator
unit.
Generator protection switch off
1、
rotor current rise, voltage
reduce violently;
2、
active and reactive power
increase;
3、
the monitor screen message: “generator
xx protection action”
4、
all meter drop to zero with
switch off, main switch “switch off” indication light of analog panel is on,
and send out speech sounds alarm signal;
5、 Indication of
generator protection unit skips position.
reasons:
1、 generator inside
failure, such as stator winding short circuit or earthing; two points of rotor
earthing; generator on fire and so on;
2、 generator outside
failure: such as generator busbar;
3、 thermotechnical
accident;
4、 emergency
protector action;
5、 operator on duty
misoperate;
6、 malfunction of
protection device and breaker mechanism.
treatment:
1、 stop automatic
excitation device;
2、 send “attention”
and “trip” signal to turbine;
3、 if the generator
trip due to main protection, such as differential protection trip, should check
all equipment in protection zone carefully; check whether relay protection is
normal; check there is smoke fog or not in generator air cooling room, open
inspection hole of generator housing, check there is smell of scorching,
smoking; measure insulation resistance of stator winding; check PT, cable and
insulation switch of generator, open the end cap of generator, check end
condition of stator winding. If there is no abnormal after the above check, can
increase voltage again. If there is no abnormal in the process of increasing
voltage, can synchronization, or shutdown to treat;
4、 if trip due to
two points of rotor earting protection action, should check all equipment in
rotor earthing protection zone, such as insulation resistance that measuring
rotor winding. After normal, can increase voltage and parallel again.
5、 if trip due to
backup protection such as combined voltage overcurrent protection action,
visual inspection for generator, if the reason is electrical system, generator
bus or auxiliary power, it is not have to check the generator inside. After
generator is insulated from failure, synchronize generator
with electric power system.
6、 if trip due to
turbine “emergency protector” action, should contact with turbine operator
timely, check the reason, if because of malfunction, after reduce speed,
synchronize generator with electric power system after recover “emergency
protector”.
7、 if trip due to
thermotechnical accident, after treatment, synchronize generator with system
again.
8、 if it is mistrip,
can increase voltage and synchronize generator with system again.
9、 In the above
process, report to shift leader timely, and treat according to the order of
shift leader.
4、Rotor ground fault:
1、 In normal operation, should check whether the earthing brush contact
of generator rotor is in good condition, when one point grounding fault, the
monitor screen showing "one point of generator rotor ground";
2、 Check excitation cable and slip ring; check whether excitation
suppression switch in CCR ground;
3、 Two points of rotor ground, excitation current leap and voltage
reduce, reactive load reduce, power factor leading phase, generator body
vibration, and two points of rotor ground protection action, generator is
disconnected.
4、
Two points of rotor loop
ground, is serious accident in power plant, should find the reason and solve it
immediately to reduce the losing.
5. Loss of excitation:
1、 Rotor loop is open, current of excitation is zero, voltage increase;
when excitation loop is open, rotor voltage is zero;
2、 When generator voltage decrease, rotor current increase, reactive
power meter showing zero or minus, power factor is leading phase;
3、 Voltage, current, active power pointer swing, generator loss of
synchronization.
6. Generator or exciter
firing:
1、 Obvious gas and adjust smell from inspection hole and air cooler;
2、 All meters indicate abnormally;
3、 Gas escape from exciter；
4、
Excitation loop meters swing
and unstable.
7. Emergency shutdown condition of generator:
2、 Stator coil temperature reach 120℃ and it does not work after adjustment inspection;
3、 Signal from turbine side, showing "turbine fault,
dangerous";
4、 Friction or collision inside the generator, abnormal vibration;
8.Generator is on fire or other hazard threaten person and equipment
safety.
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