On-site testing of diesel generator sets is a critical step to ensure their long-term stable operation and high efficiency. The testing process not only involves the start-up, automatic protection functions, steady-state and transient performance tests but also includes assessments of load capacity, continuous operation capability, and parallel operation performance. Below is a detailed testing plan, including the required equipment, procedures, and objectives, to ensure the reliability of the generator set in practical applications.
Testing Equipment and Conditions
To ensure the accuracy of the tests, both factory and on-site testing should be conducted using instruments with an accuracy level of 1.0. Before conducting any tests, the generator set must be preheated to ensure it reaches normal operating temperature. Power should be corrected according to the on-site environmental conditions.
The load configuration should be selected based on the rated power of the generator set. Pure resistive loads or inductive loads with a power factor greater than 0.8 can be used. Load variation levels should include no load, 25%, 50%, 75%, and 100% of the rated power.
For capacitive load testing, the generator set should be configured with 100% resistive load of the maximum active power output and the corresponding capacitive load to ensure a leading (capacitive) power factor of 0.95.
Start-Up Testing
The start-up test should simulate scenarios such as mains power interruption or voltage drop to a specified value, issuing commands to the automatic start mechanism to observe whether the generator set can automatically start, accelerate, build voltage, close the circuit, and supply power. After starting, the generator set should run for 1 minute and repeat the process three times, with intervals of less than 20 seconds.
Key check items during the start-up process include:
- Whether the generator set can automatically load;
- Whether the generator set can stabilize within 20 seconds after loading the rated load;
- Checking if the circuits, pipelines, and oil paths of the low-temperature start-up device are unobstructed.
Automatic Protection Function Testing
Automatic protection function testing is crucial to ensure the generator set can take effective protective measures in case of a fault. By simulating input signals, check whether the automatic protection functions of the generator set are functioning properly. Test items include:
- Low oil pressure;
- Overvoltage and undervoltage;
- Overspeed and underspeed;
- High water temperature;
- High generator temperature;
- Overload;
- Short circuit protection;
- Reverse power (measured during parallel operation);
- Overcurrent, etc.
By manually intervening with the sensor input terminal signals, observe whether the generator set can automatically shut down or issue an alarm. All protection functions must respond promptly to protect the generator set from damage.
Steady-State Operation Testing
Steady-state operation testing verifies the reliability and stability of the generator set under continuous working conditions. The test procedure is as follows:
- Continuous operation test at rated prime power: The generator set should run at full load under rated conditions for 11 hours, followed by an overload of 10% for 1 hour. Record the following parameters every 30 minutes:
- Power, voltage, current, power factor, frequency;
- Diesel engine cooling water outlet temperature or air temperature;
- Oil temperature.
- During the test, observe whether the generator set experiences shutdown, power reduction, or other abnormal phenomena. If the prime power is not indicated on the nameplate, the manufacturer should provide the corresponding prime power value for testing.
Transient Performance Testing
Transient performance testing mainly checks the generator set's response capability under sudden load changes. The test procedure includes:
- Sudden load increase from 0% to 50%;
- Gradual load increase from 50% to 100% (in steps of no less than 5%);
- Finally, a sudden load reduction from 100% to 0%.
The test should be repeated three times, and the average of the three results should be taken. This test aims to evaluate the stability and response time of the generator set under sudden load increases and decreases.
Sudden Load Reduction Testing
Sudden load reduction testing is used to verify the stability of the generator set when the load is rapidly reduced. Using a power quality analyzer to record waveforms, check the following:
- Whether the generator set can maintain stable output;
- Whether the generator set experiences protective shutdown due to sudden load reduction;
- Whether frequency or voltage abnormalities occur, leading to power equipment alarms or shutdowns.
- This test effectively evaluates the performance of the generator set under sudden load changes.
Capacitive Load Capacity Testing
Capacitive load capacity testing verifies the generator set's ability to handle capacitive loads in the power system (such as capacitive loads in power transmission lines). Test requirements include:
- The generator set should run under rated conditions for 1 hour;
- Configure 100% resistive load of the maximum active power output and a capacitive load with a leading (capacitive) power factor of 0.95;
- Record power, voltage, current, power factor, frequency, diesel engine cooling water outlet temperature, oil pressure, and generator winding temperature every 30 minutes.
This test ensures the generator set can operate stably and avoid overload when facing capacitive loads.
Continuous Operation Capability Testing
This test aims to examine the stability of the generator set under long-term continuous operation and overload conditions:
First, the generator set should run at rated power with load for 2 hours;
Then, the generator set should continue to run at 110% of the rated power for 1 hour;
During the test, record the generator set's electrical parameters and engine parameters (water temperature, oil pressure, speed, etc.), and observe whether the generator set experiences shutdown or power reduction.
Additionally, monitor the generator room temperature, generator exhaust color, mechanical component temperature (using a thermal imager), and noise levels during the test to ensure the generator set does not fail under high load and long-term operation.
Parallel Operation Performance Testing
Parallel operation system testing ensures the coordination and stability of the generator set during parallel operation. Test steps include:
Mains power outage simulation: Observe whether the generator set can automatically start and successfully parallel, and record the time from start to successful parallel operation;
Automatic load function verification: After successful parallel operation, check whether the system can automatically load;
Parallel operation logic verification: When the load decreases to a certain critical value (usually 80%), verify whether the system can automatically disconnect one diesel generator; when the load increases to 85%, verify whether the system can start another generator and connect it to the grid.
Additionally, manually simulate a main generator fault to check whether the backup generator can start normally and whether the parallel operation is correct.
Fault Simulation and Recovery Testing
When simulating a main generator fault, check whether the backup generator can start normally and complete the backup contact switch engagement to ensure proper parallel operation. After restoring the main generator, observe whether the backup generator can automatically disconnect and resume normal power supply. Additionally, simulate mains power recovery to check whether the generator set can transfer the load back to the mains according to the adjustable delay function, run under no load for 5 minutes, and automatically shut down, and whether the control device automatically resets.
Conclusion
Through comprehensive and detailed on-site testing of diesel generator sets, their efficiency, stability, and reliability in actual operating environments can be ensured. These tests not only verify the generator set's performance in terms of load changes, start-up, protection functions, steady-state, and transient performance but also provide valuable data support for subsequent troubleshooting and maintenance. Regular testing helps identify potential issues in advance, optimize generator set performance, extend its service life, and provide a solid guarantee for reliable power supply. Through scientific testing and precise analysis, diesel generator sets can more efficiently and safely provide continuous power support for various industrial and commercial facilities.
