Reverse Power on Vessel’s Diesel Generators: Measures, Precautions, and Troubleshooting

In the marine environment, it is essential to have a reliable source of power. Diesel generators are mainly used to provide power to ships and other marine vessels. During a vessel voyage, depending on power requirement (during maneuverings, canal transit, shallow waters, using bow/stern thrusters etc.) the engine crew need to run more than one generator. To run two or more generators in parallel, they need to be safely synchronized. To read and learn more about generator synchronizing, please follow THIS LINK.

Example of generator’s synchronizing panel

However, if not properly synchronized, these generators can create a dangerous condition known as reverse power. Reverse power on vessel diesel generators can pose significant risks to the overall electrical system and equipment onboard. Synchronization is crucial to ensure the smooth operation of generators, and taking appropriate measures and precautions can prevent reverse power situations. Further below, we will explore the concept of reverse power, discuss preventive measures, and outline the troubleshooting process to mitigate this issue effectively.

What is Reverse Power? 

Reverse power is a condition that occurs when a generator is operating at a higher frequency than the electrical system it is connected to. Reverse power occurs when the power flows from the bus bar or electrical network back into the generator. This situation arises during synchronization when the generator’s rotational speed, voltage, or phase sequence does not match the electrical network. Reverse power can cause damage to the generator, increase fuel consumption, and disrupt the operation of other connected generators.

Preventive Measures and Precautions

To avoid reverse power during synchronization, it is vital to implement the following measures and precautions:

    • Generator Preparation: Ensure that the generator is in good condition and properly maintained. Regular inspections and maintenance routines help identify potential issues beforehand.

    • Voltage and Frequency Matching: Prior to synchronization, verify that the generator’s voltage and frequency match the electrical network’s requirements. Use precision instruments to measure and adjust the generator’s parameters accordingly.

      Example of frequency matching

    • Phase Sequence Alignment: Confirm that the generator’s phase sequence matches that of the electrical network. Phase sequence meters or phase rotation indicators can be utilized for this purpose.

    • Protective Relays and Circuit Breakers: Install appropriate protective relays and circuit breakers to detect reverse power situations. These devices will trip and isolate the generator from the network if reverse power occurs.

Example of a reverse power protective relay

    • Synchronization Panel: Employ a synchronization panel equipped with synchroscopes, meters, and alarms. This panel provides visual and audible indications of synchronization status and alerts operators to potential reverse power conditions.

    • Engineer Training: Ensure that the engineers are well-trained in synchronization procedures and the potential risks associated with reverse power. Regular training sessions and refresher courses help enhance their understanding and vigilance.

Troubleshooting Reverse Power

In the event of reverse power occurring despite preventive measures, the following troubleshooting steps can be undertaken:

    • Immediate Isolation: When reverse power is detected, engineer should immediately disconnect the generator from the network by tripping the circuit breaker or activating protective relays

    • Fault Analysis: Examine the generator’s settings, synchronization panel readings, and any recorded alarms or indicators. Identify any potential causes such as incorrect phase sequence, voltage mismatch, or frequency deviation.

    • Corrective Actions: Depending on the fault analysis, take appropriate corrective actions. This may involve adjusting the generator’s voltage, frequency, or phase sequence to match the network requirements. Additionally, inspect and rectify any faulty relays, circuit breakers, or synchronization panel components.

    • Synchronization Retry: Once the corrective actions are completed, retry the synchronization process while closely monitoring the generator’s behavior and synchronization panel readings. Confirm that the reverse power condition has been resolved.

    • Post-Troubleshooting Inspection: Conduct a thorough inspection of the generator and associated equipment to ensure there are no hidden issues that could lead to future reverse power occurrences.

In conclusion, reverse power on vessel diesel generators can result in severe consequences, impacting both equipment and operational safety. By implementing preventive measures and precautions, vessel operators can significantly reduce the likelihood of reverse power incidents during synchronization. In cases where reverse power does occur, a systematic troubleshooting approach helps identify the root cause and rectify the issue promptly. Adhering to these best practices ensures reliable and efficient generator operation while safeguarding the vessel’s electrical system.

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