In order to help customers use generators more effectively and effectively, Saiwei Energy will share with you the common faults and solutions encountered during the use of diesel generators:

1. Abnormal increase in generator inlet air temperature

Handling:

If the outlet temperature of the generator and the temperature of the stator coil do not exceed the regulations, the output of the generator may not be reduced, but the cause should be identified and adjusted in a timely manner; When the specified value is exceeded, the generator output should be reduced first before inspection and handling.

2. Abnormal temperature rise of generator coil and iron core

Handling:

(1) If the specified value is exceeded, the load should be quickly reduced;

(2) Quickly check the temperature of the cooling air and check if the dust filter is blocked;

(3) Check if the inlet and outlet valves of the air cooler are closed.

3. Generator overload

The generator is allowed to operate under short-term overload, and the overload parameters and time must be reduced to the allowable value within the specified time.

4. The three-phase unbalanced current of the generator exceeds the standard

Handling:

When the three-phase unbalanced current of the generator exceeds the specified value, the first thing to check is whether it is caused by a fault in the transformer circuit. Otherwise, the stator current should be reduced to not exceed the specified value. At the same time, the temperature of each part of the generator should be closely monitored. When an abnormal temperature rise or an increase in unbalanced current is found, emergency disconnection and shutdown should be carried out. If the unbalanced current does not exceed 10% of the rated value during grid connection, reduce the external active power and see if the unbalanced current decreases. If it decreases, it is caused by the external network. Can maintain operation. Or disconnect from the external network.

5. During the operation of the generator, one of the indicator meters suddenly indicates abnormal or disappears

Handling:

It is necessary to refer to the instructions of other meters and check whether it is caused by damage to the instrument itself or its primary and secondary circuits. If the secondary circuit wires are damaged, try not to change the operation mode of the generator as much as possible; If it affects the normal operation of the generator, the load should be reduced or shut down according to the actual situation.

6. The secondary voltage of the PT at the generator terminal disappears

Phenomenon:

(1) The alarm bell rings, and there is an alarm for "PT disconnection at the generator end".

(2) The active, reactive, and voltmeter readings of the generator decrease or become zero.

Handling:

(1) Change the automatic excitation system to manual operation;

(2) Exit the generator compound voltage lockout overcurrent protection;

(3) Monitor and adjust the generator through other meters;

(4) Notify the turbine to pay attention to monitoring the generator.

(5) Check the PT circuit at the machine end;

(6) After normal operation, activate the generator's composite voltage blocking overcurrent protection and change the excitation regulation mode to automatic operation.

7. The excitation PT secondary voltage of the generator disappears

Phenomenon:

(1) The alarm bell rings and the "generator excitation PT disconnection" alarm is triggered.

(2) The excitation regulation screen generator terminal voltmeter indicates zero.

Handling:

(1) Change the excitation regulation mode to manual operation;

(2) Check the excitation PT circuit;

(3) After returning to normal, change the excitation regulation mode to automatic operation.

8. The generator cannot raise the voltage

Phenomenon: When the generator is boosted, the voltmeter shows no indication or is very low.

Handling:

(1) Check if the excitation regulation system is functioning properly;

(2) Check whether the meter and PT primary and secondary circuits are normal;

(3) Measure whether the insulation resistance on the high and low voltage sides of the excitation transformer is qualified.

9. Differential CT disconnection

Phenomenon: The alarm bell rings and a "differential CT disconnection" alarm is triggered.

Handling:

(1) Check whether the differential CT circuit is indeed disconnected through the current monitoring function of the protection device;

(2) If the differential CT circuit is indeed disconnected, the differential protection should be temporarily exited;

(3) Check if the wiring terminals of the differential CT circuit have good contact;

(4) Check for abnormalities in each differential CT body;

(5) After returning to normal, apply differential protection.

10. Internal faults in the generator

Phenomenon:

(1) The alarm bell rings, and there is an alarm for "generator differential protection action" or "stator grounding protection action" or "main steam valve closing".

(2) The generator meter indicator oscillates violently and reaches zero.

(3) The main switch and demagnetization switch of the generator trip.

Handling:

(1) Check and record the protection action situation.

(2) Conduct a detailed external inspection of the generator and its related equipment, as well as all electrical circuits in the protected area, to identify any faults. At the same time, inquire about any faults in the power grid. If there are indeed faults, they will be restored to operation after being eliminated.

(3) If no obvious fault points are found, after measuring the insulation resistance of the stator and rotor coils and passing the test, the shift supervisor can apply to boost the generator from zero. If any abnormalities are found during the boost, the generator should be immediately shut down. If no abnormalities are found, it can be integrated into the power grid for operation.

11. External fault of the generator

Phenomenon:

(1) The alarm bell rings, and the computer alarm lights up for the "generator compound voltage blocking overcurrent protection action".

(2) The stator ammeter suddenly increases sharply and the voltage drops sharply.

Handling:

When the external fault of the generator lasts for a long time, the ammeter indicates the maximum value, and the voltage drops sharply, the duty officer should immediately manually disconnect the generator; If the timed overcurrent protection cuts off the main switch of the generator, and the internal fault protection does not act, and no obvious abnormal phenomena are found through external inspection, the generator can be connected to the grid for operation after other systems are normal.

12. One point grounding of generator rotor

Phenomenon: The alarm bell rings and the rotor is grounded at one point.

Handling:

(1) Check the grounding situation inside the protection device and whether the two-point grounding protection is in the tripping position. Otherwise, immediately switch it to the tripping position;

(2) Check for overheating, dust accumulation, and oil stains at the rotor slip ring, and try to clean it;

(3) When there is a loss of excitation in the generator during the process of grounding at one point or searching for a grounding at another point, it should be immediately disconnected and shut down;

(4) If it is determined that there is a grounding point inside the rotor, the shift supervisor should be applied for shutdown.

13. Generator to synchronous motor operation

Phenomenon:

(1) The alarm bell rings, and the computer alarm lights up when the main steam valve is closed.

(2) The active meter of the generator indicates below zero, while the reactive meter indicates an increase.

(3) The stator current of the generator decreases and the stator voltage increases.

(4) The excitation voltage and current slightly decrease.

(5) The incoming line may be overloaded or the pointer may be full.

Handling:

(1) The main steam valve trip generator protection should be triggered to disconnect and shut down, otherwise it should be manually disconnected and shut down.

(2) If the main steam valve is closed and a notice of "machine danger" is received from the turbine owner, the generator should be manually disconnected immediately.

14. Generator oscillation

Reason:

(1) Due to system malfunction;

(2) Caused by generator demagnetization or underexcitation;

(3) Misoperation by personnel.

Phenomenon:

(1) The stator ammeter oscillates back and forth, usually exceeding the rated current.

(2) The pointer of the stator voltmeter swings violently, usually resulting in a decrease in voltage indication.

(3) The pointer of the active and reactive power meters swings violently.

(4) The generator produces rhythmic sounds and oscillates with the meter.

(5) If the generator oscillates synchronously with the system, the generator meter and system meter will oscillate uniformly; If there is oscillation between the generator and the system, the generator meter will swing opposite to the system.

Handling:

(1) If a stable oscillation occurs, there is no need for operation, but preparations should be made to handle the accident.

(2) If there is no decreasing trend in oscillation, the steam turbine should be immediately notified to reduce the active load of the generator and increase the excitation current of the generator. When using automatic excitation, it is strictly prohibited to interfere with the operation of the regulator.

(3) If the oscillation is caused by incorrect parallel connection of the generator, the generator should be immediately disconnected.

(4) If the duty officer fails to synchronize the generator within two minutes after taking measures, the generator should be disconnected.

15. Non full phase operation during generator disconnection

Phenomenon: When the generator is disconnected, the stator three-phase ammeter indicates imbalance, causing the unit to vibrate.

Handling:

(1) Manually pull the switch again. If unsuccessful, contact the turbine to maintain a speed of 3000r/min and re synchronize the generator into the system.

(2) After integration into the system, contact the device area to reverse the load and use the upper level switch to disconnect the generator.

(3) If the generator cannot be integrated into the system, the upper level switch of the generator and the line switch on the generator side busbar should be immediately opened.

16. Generator main switch tripped

Handling:

(1) Immediately check if the demagnetization switch has tripped, otherwise it should be manually disconnected immediately.

(2) Check the status of the system connection line and further handle it according to the operating procedures of the main system;

(3) Check what type of protection action, the value of the protection action, determine the fault, and report to the leader for handling;

(4) If it is a human error, the generators can be paralleled without inspection.

17. Generator demagnetization

Phenomenon:

(1) The alarm bell rings and the "demagnetization protection action" computer alarm lights up. The reactive load of the generator drops below zero.

(2) The excitation voltage of the generator decreases and the excitation current reaches zero.

(3) The stator voltage of the generator decreases, and the stator current significantly increases.

(4) Active power swings and decreases, while reactive power indicates below zero.

(5) The line current is full or the opposite side switch trips.

Handling:

(1) When the generator loses excitation, the demagnetization protection should act to disconnect the generator; When the demagnetization protection is not activated or the switch refuses to trip, manual disconnection and shutdown should be carried out immediately.

(2) After disassembly, check and handle the excitation circuit of the generator. If there are no problems, integrate the generator into the system.

18. Non synchronous parallel connection of generators

Phenomenon:

At the moment of closing the main switch of the standby generator, the stator current suddenly increases sharply, the stator voltage decreases, the generator body emits a roar, and then the stator current swings violently or causes the protection action to trip.

Handling:

(1) If the protection is not activated, the main switch and demagnetization switch of the generator should be manually disconnected immediately.

(2) After the generator stops rotating, measure the insulation resistance of the stator coil.

(3) Open the generator end cover and check for any deformation at the end of the stator coil.

(4) After confirming that the generator was not damaged and the reason for non synchronous parallel operation, with the approval of the chief engineer, the generator was once again integrated into the system.

19. Generator or excitation transformer catching fire

Reason:

(1) Winding insulation breakdown;

(2) The wires and connectors are overheated.

Phenomenon:

(1) Sparks and smoke can be seen in the peephole of the generator;

(2) The excitation transformer body is smoking and catching fire;

(3) There is a strong insulation smell around the excitation transformer of the generator.

Handling:

(1) Immediately disconnect and shut down.

(2) If the fire does not decrease after disconnection, water should be injected into the generator and the excitation transformer 1211 fire extinguisher should be used to extinguish the fire.

(3) Maintain the generator running at 300r/min.

(4) Protect the accident scene and analyze the cause of the accident.

20. Generator oscillation and loss of step

Phenomenon:

The power generated by the generator during normal operation is balanced with the user's load power, and both the generator and the system operate in a stable state. When significant disturbances occur in the system, the active power balance between the generator and the user will be disrupted. At this point, the output power of the generator must be changed immediately.

However, due to the rotational inertia of the generator rotor, the action of the turbine governor requires a certain delay. Therefore, changing the power of the generator requires a process. In this process, the power of the generator cannot be balanced with the power of the user, which will disrupt the stable operation of the generator and cause oscillation.

Handling:

If the accident is not serious and the speed regulation of the steam turbine is sensitive, the current, voltage, and power of the generator will recover to power balance after a short period of fluctuation. If the accident is serious and the speed regulation of the steam turbine is slow, it will cause intense oscillation between individual generators and the system, and at the same time, absorb power from the system. This power transmission back and forth may develop to the point of losing synchronization between the generator and the system.

Guangzhou Saiwei Energy Technology Co., Ltd. is a comprehensive enterprise specializing in design, production, and generator installation. Guangzhou Saiwei has many years of experience in engineering design and installation services. For many years, Guangzhou Saiwei has been committed to providing every customer with comprehensive products and energy solutions, including technical consulting, whole machine and generator supply, operation training, etc., with leading technology and first-class quality. The product range covers land diesel generator sets, marine generator sets, high-voltage generator sets, etc., and is widely used in industries such as power, communication, iron towers, healthcare, financial systems, data centers, etc. Welcome to inquire: 13302262088