Paralleling generators involves synchronizing the generators to operate at the same frequency and phase and then connecting them together using the correct wiring and cables. Paralleling generators can be a complex and potentially dangerous process, so it is important to follow proper procedures and consult with a qualified professional if necessary.Â
In this blog, we will provide a step-by-step guide for paralleling generators, as well as discuss this technique’s conditions, tools, and benefits.
Key Takeaways
- Paralleling generators involves synchronizing the generators to operate at the same frequency and phase and then connecting them together using the correct wiring and cables.
- Synchronizing generators refers to the process of connecting two or more generators together in such a way that they operate at the same frequency and phase.
- Specialized tools and equipment may be required when paralleling generators, such as a synchroscope, frequency meter, and protective gear.
- Paralleling generators require that the generators have similar ratings and are in good working condition.
- Paralleling generators can be a complex and potentially dangerous process, so it is important to follow proper procedures and consult with a qualified professional if necessary.
Paralleling in generators refers to connecting two or more generators to work together to provide a single, larger output.
This is achieved by connecting the output terminals of the generators together, which allows the power from each generator to be combined and used simultaneously
There are several conditions that must be met to safely and effectively parallel generators. These include:
- Voltage Magnitude: The voltage levels of the generators must be similar to ensure equal power sharing. Voltage differences may lead to circulating currents, causing unnecessary stress on the equipment and reducing efficiency. A mismatch in voltage magnitude can be corrected by adjusting the generator’s excitation system.
- Frequency: The generators must operate at the same frequency to prevent torque fluctuations and oscillations. A mismatch in frequency can lead to mechanical stress, overheating, and potential damage to the generators or connected equipment. To synchronize the frequencies, the speed of the prime mover (typically a gas or steam turbine, diesel engine, or water turbine) must be adjusted.
- Phase Sequence: The generators must have the same phase rotation to prevent short circuits and damage to the equipment. Phase sequence is typically defined as either clockwise (ABC) or counterclockwise (ACB) order. To ensure proper phase sequence, the generator connections must be verified and corrected if necessary.
- Phase Angle: The phase angle between the voltage waveforms of the generators must be zero or near zero to ensure stable operation. A significant difference in phase angles can lead to high transient currents during synchronization, damaging the equipment and potentially causing a system failure. To achieve proper phase alignment, the generator’s speed must be carefully controlled and monitored.
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To parallel generators, operators typically use a synchronization panel, which includes instruments such as voltmeters, frequency meters, synchroscopes, and circuit breakers.Â
The panel monitors the generator’s output parameters, and the operator can make adjustments as needed to fulfill the conditions mentioned above.Â
Additionally, automatic synchronizing systems can be employed to simplify the process and reduce human intervention.
| Tool/Instrument | Function |
|---|---|
| Voltmeter | Measures the voltage magnitude of the generators to ensure they are similar. |
| Frequency meter | Monitors the generator frequency to ensure synchronization. |
| Synchroscope | Indicates the relative phase angle and speed difference between the generators for proper alignment. |
| Phase sequence indicator | Verifies the phase sequence (phase rotation) of the generators to prevent short circuits. |
| Protective relays | Provides protection against over-current, over-voltage, and other abnormal conditions during synchronization. |
| Circuit breaker | Allows for safe connection and disconnection of the generators to the power distribution system. |
| Control switches and panel | Enables manual adjustments of the generator's excitation system and prime mover speed to achieve synchronization. |
| Automatic synchronizing system (optional) | Automatically adjusts generator parameters to achieve synchronization, reducing the need for manual intervention. |
Above all you typically need a transfer switch installed when paralleling a generator with another generator or with the utility grid.
A transfer switch is an essential component for safe and efficient operation when connecting generators in parallel. It ensures that the power sources are properly synchronized, prevents back-feeding into the grid, and isolates the loads between the power sources.
Step 1: Preliminary checks
Verify that the generator’s output voltage, frequency, and phase sequence are set according to the system requirements.
Ensure that the generators are in good working condition and all protective devices are functioning properly.
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Step 2: Start the first generator
Start the first generator and connect it to the power distribution system. Allow it to stabilize and reach the desired voltage and frequency.
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Step 3: Start the second generator
Start the second generator without connecting it to the power distribution system. Allow it to stabilize and reach the desired voltage and frequency.
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Step 4: Monitor and adjust parameters
Using the voltmeter and frequency meter, monitor and compare the output parameters of both generators. Adjust the excitation system and prime mover speed as necessary to match the voltage magnitude and frequency.
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Step 5: Check phase sequence and phase angle
Use a phase sequence indicator to verify that both generators have the same phase rotation. If required, correct the connections.
Observe the synchroscope to ensure the phase angle is near zero, indicating proper alignment between the generators.
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Step 6: Synchronize the generators
When the parameters match and the phase angle is near zero, close the circuit breaker to connect the second generator to the power distribution system.
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Step 7: Monitor and adjust load sharing
Monitor the load sharing between the generators and adjust the prime mover’s speed or automatic load sharing controls to balance the load distribution.
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Step 8: Repeat for additional generators
If more generators need to be paralleled, follow the same steps for each additional generator.
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Step 9: Ongoing monitoring
Regularly monitor the generator output parameters and load sharing to ensure stable operation and make adjustments as needed
When generators are operating in parallel, they share the load demand to ensure stable and efficient power distribution.
Load sharing is achieved by balancing the real and reactive power output of each generator. This balance is maintained by carefully adjusting the prime mover’s speed or governor settings and the generator’s excitation system.
In some cases, automatic load-sharing controllers can be used to maintain this balance, reducing the need for manual intervention and ensuring an optimal load distribution among the interconnected generators.
If two generators are not properly synchronized, it can lead to several adverse effects. These include high transient currents during the connection process, which can cause mechanical stress, overheating and potential damage to the generators or connected equipment.
Unsynchronized generators may also cause torque fluctuations and oscillations, leading to reduced system efficiency and stability. In extreme cases, unsynchronized generators can result in short circuits or system failures, posing significant risks to both equipment and personnel or in worst cases it may explode.
Yes, it is possible to synchronize two generators of different frequencies.
But synchronizing two generators with different frequencies is not recommended, as it can lead to undesirable consequences, such as mechanical stress, overheating, and potential damage to the generators or connected equipment.
To parallel generators, they must first be adjusted to operate at the same frequency by controlling the speed of their respective prime movers. Once their frequencies match, the generators can be synchronized according to the standard procedure, ensuring proper load sharing and stable operation.
Paralleling AC generators can present several challenges, including matching voltage magnitudes, frequencies, phase sequences, and phase angles.
Other issues that may arise during the paralleling process include circulating currents caused by voltage imbalances, harmonic distortion, and fluctuations in system frequency or voltage due to changes in load demand.
Additionally, proper load sharing among parallel generators must be maintained, which requires continuous monitoring and adjustment of the generators’ output parameters.
Paralleling two identical AC generators to obtain 240V can be achieved if both generators are designed to produce 240V, and the standard synchronization conditions are met.
However, if the generators are designed to produce 120V each, paralleling them in this manner is not recommended.
Connecting two 120V generators in series to obtain 240V can lead to load imbalance, reduced system efficiency, and potential damage to the generators or connected equipment.
Instead, it is advisable to use a single generator specifically designed to produce the desired voltage or consult with a professional to explore other options for obtaining 240V safely.
Can you parallel different-size generators?
It is generally possible to parallel different-size generators, but it can be a complex and potentially dangerous process. To safely parallel generators of different sizes, they must be adequately synchronized and connected, which requires specialized equipment and expertise.
Can I run two different brand generators in parallel?
It is possible to run multiple generators in parallel, but whether or not you can run two generators from different brands at the same time will depend on the specific generators and the setup of your system.
Do parallel generators double the wattage?
It depends on the type of generator and how it is set up. In general, running two generators in parallel can increase the amount of power they can produce, but it will not necessarily double the wattage. This is because each generator has its own maximum output, and the combined output of the two generators will be limited by the lower of the two outputs.
Imran
Hi, I'm Imran, a seasoned expert in home and outdoor gadgets. My passion is to make living spaces smarter, safer, and more efficient. With over 7 years of experience in the world of smart thermostats, power stations, home security systems, and lawn care tech, I can provide you with the best solutions for your indoor and outdoor sanctuaries.
