Complete Guide to Diesel Generator Testing

Diesel generators play an essential role in many situations. Whether used as a backup power source or the main power source, their performance and reliability directly affect the normal operation of equipment and the safety of personnel. Therefore, it is essential to test diesel generators regularly. This article provides a detailed introduction to the entire process of diesel generator testing, including preparation before testing, precautions during testing, and inspection after testing, helping you ensure that the generator is always in the best condition.

Before starting the test, adequate preparation must be made to ensure the smooth progress of the test and avoid any potential safety hazards.

Generator Facility Inspection: First, carefully check whether the generator's appearance is damaged or abnormal. Check whether the generator housing has cracks, deformation, or other visible damage. Such damage may affect the normal operation of the diesel generator or even lead to safety hazards. Check whether the fixing bolts of the generator are tightened. Loose bolts may cause vibration during operation, affecting its performance and service life. Ensure all connecting parts are firm and reliable.

Oil Level Inspection: Check whether the engine oil level is within the normal range. Engine oil is crucial for the lubrication of the generator. If the oil is insufficient, the engine may overheat or even be damaged. Generally, the oil level should be between the upper and lower marks on the dipstick. Check whether the diesel level is sufficient. Diesel is the power source of the generator, and an insufficient fuel level will cause the generator to fail to start or operate normally. Ensure that the diesel level is above two-thirds of the fuel tank to guarantee sufficient fuel during the test.

Filter Inspection: Check whether the engine oil filter, air filter, and fuel filter need replacement. The purpose of the filters is to remove impurities and keep the oil and air clean. If the filters are clogged, the generator's performance and service life will be affected. Generally, the service life of filters is 100–200 hours, depending on the operating environment and frequency.

Ventilation System Inspection: Check whether the ventilation and exhaust system in the generator room is operating normally. Proper ventilation is crucial for generator cooling. Poor ventilation will cause overheating, affecting performance and service life. Ensure that the air supply and exhaust fan blades are clean and rotating properly, and that the air ducts are unobstructed.

Before testing, the generator must be disconnected from the power grid to ensure that the test process will not interfere with the grid and to avoid reverse power supply from the grid to the generator, ensuring testing safety. Wait until the generator completely stops rotating before proceeding with the next steps.

During the testing process, it is necessary to strictly follow the operating procedures, closely monitor various operating parameters of the generator, and ensure the safety and reliability of the testing process.

Correct Use of the Multimeter: Select an appropriate multimeter for measurement. It is recommended to use a model with a wide range to ensure measurement accuracy. Before measurement, check whether the multimeter battery is sufficient and whether the probes have good contact. Follow the correct operation method for measurement. When measuring voltage, insert the red probe into the "V/Ω" port and the black probe into the "COM" port. Set the multimeter to the appropriate voltage range, then connect the probes to the corresponding generator terminals. When measuring current, the multimeter must be connected in series in the circuit, ensuring the correct current flow direction.

Monitoring Operating Values: During testing, pay close attention to the operating values of the generator, such as voltage, current, and frequency. If any abnormality is found, stop the generator immediately and notify the supervisor. For example, if the voltage value exceeds the normal range (e.g., 400V ±5%), the voltage regulation system may have a problem; if the current increases abnormally, it may indicate an overload or short circuit fault.

Inspection of Wiring Conditions: Check whether the wiring of the voltage regulator, speed governor, and other devices is correct. Incorrect wiring may cause the generator to fail to operate normally or cause abnormalities. Ensure all wiring is firm and reliable, with no looseness or poor contact.

Starting the Generator: On the main control panel, set the switch to "Manual" and "Emergency" positions, and turn off the heater switch. Close the auxiliary control panel door and power it on, then close the knife switch. The green signal light should be on. Press the "Close Circuit Breaker" button, at which point the breaker should close, the red light should illuminate, and the main control panel heater should be connected with its indicator light on. Start the generator to run at full speed. At this time, the green "Breaker Open" light on the main control panel should be on. Adjust the voltage adjustment knob on the main control panel so that the generator voltmeter points to 400V. Set the generator speed switch to "Idle" for 3 minutes, then turn off the diesel engine power switch to the "Off" position and reset the idle switch to "Run."

Recording Operating Parameters: During testing, record in detail the operating parameters of the generator, including voltage, current, frequency, and speed. These data are crucial for evaluating the generator's performance and stability. They can be read from the instruments on the main control panel and recorded in the test report.

Checking Automatic Start Function: If the generator set is in the automatic start standby mode, set the switches on the diesel engine instrument panel to "Off" and "Run." The coolant and lubricating oil heater circuits should be connected, preparing for automatic operation. Set the main control panel switches to "Automatic" and "Emergency" positions; the "Automatic On" indicator should light up. Turn off the water and oil heater switches, then open the auxiliary control panel knife switch to the off state. The auxiliary control switch should delay opening, and the generator should start automatically. If the generator starts successfully, the green light on the main control panel will be on. When the automatic switch on the main control panel is closed, the green light goes out and the red "Breaker Closed" light turns on, indicating that the generator has automatically started successfully, the breaker is closed, and power is being supplied.

After testing is completed, a series of inspections must be conducted to ensure the generator has returned to normal status and that the generator room is free from safety hazards.

Checking Generator Status: After completing the testing work, testers should inspect the generator and site facilities in the generator room to ensure restoration to hot standby status. Check whether the oil level and water level of the generator are normal, whether filters need replacement, and whether the ventilation system is operating properly.

Checking Generator Room Facilities: Check for potential hazards such as leaks in the generator room. Inspect the floor, walls, and pipelines for traces of oil, water, or other liquid leaks. If any leakage is found, identify the cause and handle it promptly to prevent damage to equipment and the environment.

Recording Test Results: Test personnel should record detailed data from this test, including test time, testers, testing equipment, operating parameters, abnormal conditions, and corrective measures. These records are significant for subsequent equipment maintenance and fault analysis.

Analyzing Test Data: Analyze the recorded test data to evaluate the overall performance of the generator. If any abnormalities or potential problems are found, report them promptly and take appropriate measures. For example, if the generator voltage fluctuates significantly, there may be an issue with the voltage regulation system that requires further inspection and repair.

Confirming with the Supervisor: After completing all inspection work, confirm with the supervisor that the generator and generator room status are normal. Ensure that all equipment has been restored to normal condition and that there are no safety hazards.

Locking and Leaving the Generator Room: After confirming that everything is correct, lock the generator room to ensure equipment safety. Before leaving, check again whether all doors and windows are closed and power sources disconnected to prevent accidents.

During the testing process, some special situations may arise that require prompt and correct measures to be taken.

When the generator set automatically starts generating power, if overload or overcurrent tripping occurs, the diesel engine should idle automatically and issue an audible and visual alarm. If the fault is eliminated manually within 3 minutes, switch from "Automatic" to "Manual," then back to "Automatic," and the generator set will automatically resume normal power supply. If the fault is not resolved within 3 minutes, the generator set will automatically shut down.

During the test run, if oil pressure is too low or water temperature too high, the generator set will automatically stop immediately and issue an audible and visual alarm. Stop immediately to check and identify the cause, such as insufficient oil, oil pump failure, coolant blockage, or low coolant level. After troubleshooting, restart the generator.

Check whether the alarm circuit is working properly. Press the "Alarm Test" button; the alarm bell should ring, the "Fault Alarm" light should illuminate, and both audible and visual alarm signals should activate. When the button is released, the alarm signal should stop immediately. If the alarm circuit fails to operate normally, check the wiring and alarm device promptly to ensure it functions correctly in an emergency.

Testing a diesel generator is a complex and critical process that must be carried out strictly according to operating procedures to ensure testing safety and accuracy. Through this detailed introduction, you can gain a comprehensive understanding of each stage of diesel generator testing, including preparation before testing, precautions during testing, and inspection after testing. It is hoped that this information will help you better manage and maintain your diesel generator, ensuring it can operate normally at crucial moments and provide reliable power protection for your equipment and personnel.