Correct Operation and Maintenance of Diesel Generator Set

I. Pre‑start Preparation and Inspection of Diesel Generator Set

1. The diesel generator shall not be started until all pre‑start checks and preparations are completed, and the operation mode selector switch shall be set to the “OFF” position.
2. Before starting or putting the diesel generator into service, verify that the battery charging power supply, control & signal system power supply, cooling water temperature control, air system, fuel system and lubricating oil system are functioning normally.
3. Switch on the battery charging power supply. Confirm the charging indicator red light is on and the battery voltage is approximately 24V‑30V. The battery capacity shall be sufficient to support 9 consecutive start‑up cycles of the unit.
4. Check that the cooling water temperature heater power supply is switched on and its red indicator light is illuminated.
5. Verify normal oil level of the indoor fuel storage tank (capable of supporting 8‑hour full‑load continuous operation of the unit). Open the fuel inlet valve of the diesel generator; fuel delivery shall adopt manual mode.
6. Vent air from the fuel system before start‑up; otherwise, the engine may fail to start normally.

 II. Further Pre‑start Inspection of Diesel Generator Set

1. All work permits for the diesel generator set have been closed; no personnel are working on the diesel engine and no obstacles exist around the unit.
2. Check that the lubricating oil level of the diesel generator is normal.
3. Check that the cooling water level of the diesel generator is normal.
4. Verify proper pre‑heating of the diesel generator.
5. Ensure no oil leakage or water leakage on the unit; keep the interior clean and free of debris, and clear obstructions from the exhaust outlet.
6. Keep the instrument panel clean inside and out with no foreign objects; confirm electrical circuits are in normal condition and no alarms are present on the control panel.
7. Confirm all switches are positioned correctly for start‑up; verify the emergency stop button on the local instrument panel of the diesel generator is in correct position, and the generator outlet circuit breaker is in the open position.
8. Before start‑up, measure insulation resistance of the diesel generator set using a 1000 V megohmmeter; the reading shall be no less than 0.5 MΩ.

III. Starting and Stopping the Diesel Generator

1. Three start‑up modes are available: automatic start, remote start (soft operation via CRT screen), and manual start on the local control panel.
2. Stop modes include: remote stop (soft operation via CRT screen), stop or emergency stop via local control panel, emergency stop on engine body control panel, and mechanical shutdown on engine body.
3. The diesel generator is fitted with an operation mode selector switch with three positions: **AUTO**, **MANUAL**, and **STOP**.
4. **Automatic Mode**: This is the normal operating mode. Setting the selector switch to “AUTO” puts the diesel generator set into automatic start‑up standby status.
5. **Remote Start‑Stop Mode**: Set the selector switch to “MANUAL” to enable remote control, allowing remote start‑up and shutdown of the diesel generator.
6. **Local Manual Start‑Stop Mode**: Set the local position selector switch to “LOCAL” for local manual start‑up and shutdown.
7. For manual start‑up: switch the operation mode selector to “MANUAL”, close the generator start switch. Close the generator outlet circuit breaker once rotational speed and voltage reach rated values.
8. The diesel engine is equipped with an automatic synchronizing device. For test purposes, it may be synchronized and paralleled with station service power for load‑carrying test runs. Set the selector switch to “TEST”, close the generator start switch; the outlet circuit breaker will automatically parallel with station service power upon achievement of rated speed and voltage.
9. Immediately perform on‑site inspection after generator start‑up. Check for abnormal noise, excessive vibration, water/oil leakage, loose bolts and nuts, broken circuits, and loose pipe joints. Verify normal exhaust smoke color. Confirm the following parameters: rotational speed, lubricating oil pressure, lubricating oil temperature, cooling water temperature, voltage and frequency.
10. Before shutting down a running diesel generator, confirm that the working power supply for the essential busbar has been restored.
11. Open the generator outlet circuit breaker. Allow the unit to run at no‑load for 3‑5 minutes, then open the generator start switch.

IV. Normal Operation of Diesel Generator

1. The diesel generator may run continuously under rated conditions. Monitor and ensure operating parameters stay within specified limits:

2. The running unit shall exhibit no abnormal vibration, and exhaust smoke shall be of normal colour.
3. Under normal operation, set the operation mode selector switch to “AUTO”.
4. The unit shall reach rated speed and voltage within 10 seconds after start‑up. If essential busbar voltage recovers within 10 seconds, the generator outlet breaker remains open; if the essential busbar remains undervoltage, the breaker closes automatically to supply power to the essential busbar.
5. Prohibit prolonged idling of the diesel generator set. Shut down the unit for standby if no load is connected.
6. Exhaust pipes reach high temperatures during operation. Keep personnel clear to avoid burns. Ensure no oil‑soiled materials or other combustibles are present near exhaust pipes to prevent fire hazards.
7. After unit shutdown, the coolant remains at high temperature. Do not open the radiator cap, and do not add coolant to a hot cooling system; severe engine damage may occur.
8. Do not restart the unit before faults are rectified and reset. Do not press the fault reset button under MANUAL or AUTO mode until faults have been eliminated.

 V. Inspection Items and Routine Periodic Tests

1. Routine inspection items for diesel generator under automatic mode
2. Check the unit for any leakage.
3. Confirm lubricating oil level is normal.
4. Confirm cooling water level is normal.
5. Check oil levels of storage tank and daily service fuel tank.
6. Confirm the local position selector switch is set to “AUTO”, the essential section working power switch is closed with indicator light on, emergency stop button is correctly positioned, and no alarms appear on the control panel.
7. Verify battery charging indicator is lit and battery voltage is normal.
8. **Diesel Generator Tests**
9. Perform local start‑up test on day shift of odd‑numbered Sundays.
10. Perform remote start‑up test on early shift of even‑numbered Sundays.
11. Carry out engine start‑up and load‑carrying test prior to commissioning.

 VI. Protection and Signals of Diesel Generator Set

1. Diesel Engine Protection

(1) Protections triggering shutdown: high cooling‑water temperature (above 95 °C); low lubricating‑oil pressure (below 0.5 MPa); reverse‑power shutdown; overspeed.
(2) Protections triggering alarm signals: high water temperature; low lubricating‑oil pressure; high lubricating‑oil temperature; low oil level; ground fault.

2. Generator and Feeder Protection

(1) Over‑current protection: for internal short‑circuit faults of generator.
(2) Over‑load and ground‑fault detection device: for alarm signal output only.
(3) The generator excitation system shall be equipped with automatic voltage regulator (AVR) fault protection.
(4) Brushless excitation system shall be fitted with rectifier diode fault protection.
(5) Short‑circuit and overload protection for feeders are realized via semiconductor releases integrated within outlet circuit breakers.
(6) Main feeders and branch feeders shall be equipped with phase‑to‑phase short‑circuit protection and overload protection. The whole power‑feeding system shall be fitted with single‑phase ground‑fault detection. Phase‑to‑phase short‑circuit protection triggers circuit‑breaker tripping; overload and ground‑fault detection output alarm signals. Short‑circuit and overload protection for feeders are implemented by built‑in semiconductor releases of circuit breakers.

 3. Signals

Signal systems are available both on the unit control cabinet and in central control room computers:

1. Unit running signal
2. Unit start‑up failure signal
3. Unit overspeed signal
4. Low / excessively‑low lubricating‑oil pressure signal
5. High / excessively‑high cooling‑water temperature signal
6. Low fuel‑tank level signal
7. 24 V DC power supply loss signal
8. 110 V DC power supply fault signal
9. Rotating rectifier diode fault signal
10. Automatic voltage regulator fault signal
11. General unit fault signal
12. Unit abnormal operation signal *
13. Operation‑mode selector switch position signal *
14. Fuse blown signal for essential‑section power auto‑switch circuit
Note: Marked with “*”: these signals are available locally and also wired via passive contact outputs to the main unit unit control room.