Generator Set Winding Overheating and Mitigation Measures

Overheating alarms in generator set windings are a common and hazardous fault signal in equipment operation, indicating that the winding temperature has exceeded the allowable temperature rise limit designed for the winding. The allowable temperature rise refers to the maximum temperature the winding can endure, typically defined as the difference between the winding's actual temperature and the surrounding ambient temperature. When the winding temperature becomes too high, it can cause equipment damage, electrical failures, and even serious safety accidents. Therefore, once a high-temperature alarm is triggered, immediate and effective measures must be taken to prevent further deterioration.

This article will analyze the common causes of generator set winding overheating, explain the dangers of high-temperature operation on the equipment, and propose corresponding preventive and maintenance measures to ensure the stable and safe operation of the generator set.

Common Causes of Generator Set Winding Overheating

Generator set winding overheating may result from electrical, mechanical, operational, or environmental factors. These causes often interact, leading to increased winding temperature and affecting the normal operation of the generator set. Below are some of the most common causes.

1. Electrical Factors

Electrical faults are one of the primary causes of winding overheating, with issues such as abnormal voltage and winding short circuits being the main contributors.

Winding Short Circuit

A short circuit in the winding, such as inter-turn, inter-phase, or ground short circuits, causes abnormal current flow, resulting in rapid current increase within the winding and local overheating. This condition worsens, especially when the winding's insulation is damaged.

Abnormal Voltage

High Voltage: When the voltage exceeds 10% of the rated value, electromagnetic losses (such as iron losses) increase, causing both the generator set core and winding temperature to rise.
Low Voltage: When the voltage falls more than 5% below the rated voltage, the generator set will draw excessive current under rated load, causing overheating and negatively impacting the winding insulation.
Phase Voltage Imbalance: If the imbalance of three-phase voltage exceeds 5%, the resulting current imbalance will cause uneven heating in the generator set, leading to winding overheating.
Single-phase Operation: In single-phase operation, the remaining two-phase windings must carry higher current, leading to overheating or even winding failure.

2. Mechanical Factors

Mechanical faults also significantly affect winding overheating, mainly related to the rotor, bearings, and load.

Bearing Issues

Damage or inadequate lubrication of the bearings increases friction between the rotor and stator, generating additional heat. Prolonged friction not only causes bearing overheating but also impacts the generator set's cooling performance, leading to increased winding temperature.

Abnormal Mechanical Load

If the generator set operates under load faults or overloads, it will run under high load conditions for extended periods. This increases current flow, causing the winding to heat up. The temperature will rise even more when there are significant load fluctuations, as the generator set has to bear larger power variations.

3. Operational and Environmental Factors

The operating conditions of the generator set and the ambient temperature can also directly influence its temperature level.

Frequent Starts

Each time the generator set starts, the starting current is typically more than twice the rated current. Frequent starts place the winding in a high-temperature state for extended periods. This is especially problematic under high-load conditions, where frequent starts accelerate insulation aging and prevent timely heat dissipation, making overheating more likely.

Poor Ventilation

The cooling system of the generator set is crucial for its operation. Blocked ventilation ducts or the accumulation of dust and oil on the winding surface will significantly reduce heat dissipation efficiency, causing the winding temperature to rise.

High Ambient Temperature

If the generator set operates in a high ambient temperature, especially in summer or tropical regions, the winding’s cooling performance declines, leading to higher operating temperatures. Additionally, high humidity can affect insulation material properties and accelerate winding aging.

Dangers of High-Temperature Operation in Generator Sets

Long-term operation at high temperatures accelerates the aging of the winding insulation materials, which can eventually cause equipment failure or even burning. Below are the main dangers associated with high-temperature operation.

1. Insulation Material Aging and Damage

The insulation layer of the winding is an important barrier preventing current leakage. Long-term high-temperature operation accelerates the aging of the insulation, causing it to thin and become brittle. When the insulation begins to carbonize, inter-turn short circuits, inter-phase short circuits, or ground short circuits may occur, leading to local winding damage and eventually causing downtime and costly replacements.

2. Additional Load Due to Single-Phase Operation

During single-phase operation, the remaining two-phase windings are forced to bear more current, which increases winding temperature. When a single-phase fault occurs, the asymmetric distribution of current in the winding can not only lead to overheating but also cause overloads that may burn out the winding.

3. Mechanical Damage and Increased Vibration

High temperatures also affect the generator set's rotor and other moving parts. Overheating can cause parts to expand and deform, disrupt bearing lubrication, and even cause mechanical damage or failure due to excessive vibration. This can significantly impact the generator set's stability and lifespan.

4. Cable and Connection Component Damage

Overheating in the generator set can also affect the insulation of cables and connection components. In cases of overload operation, overcurrent conditions accelerate the aging of the cable insulation, potentially leading to cable damage and short circuit failures.

Preventive and Maintenance Measures

To prevent generator set winding overheating and related faults, the following preventive and maintenance measures are essential.

1. Electrical Management and Monitoring

Regular Voltage and Current Checks: Ensure that the generator set's voltage remains within the rated range to prevent overheating due to excessively high or low voltage. Use current monitoring devices to track current changes in real-time and prevent issues such as voltage imbalance or single-phase operation.

Winding Insulation Inspection: Regularly use insulation resistance testers to check the health of the winding insulation. Ensure that the winding maintains good insulation performance during operation to reduce the risk of short circuits and overheating.

2. Mechanical Maintenance

Check Bearings and Lubrication Systems: Regularly inspect the bearings and lubrication system to ensure they are undamaged and well-lubricated, reducing frictional heat generation.

Inspect Load Equipment: Ensure that load equipment is in good condition to avoid mechanical faults or overloads, which can place undue strain on the generator set and lead to overheating.

3. Operational and Environmental Controls

Reduce Startups: Avoid frequent startups, especially under heavy load conditions. The surge current during startup has a significant impact on the winding. If necessary, conduct rotor dynamic balancing tests to reduce startup load shocks.

Clean Ventilation Ducts and Winding Surfaces: Regularly inspect and clean the ventilation ducts to avoid dust and oil buildup, ensuring that cooling efficiency remains high and the generator set remains clean.

Regulate Ambient Temperature: In high-temperature environments, use fans or air conditioning to reduce the temperature and ensure the generator set operates in an optimal environment.

Conclusion

A generator set winding overheating alarm is an early warning signal of potential equipment failure. If ignored, it could lead to significant damage or even a shutdown. Through regular electrical inspections, mechanical maintenance, and environmental temperature control, generator set overheating faults can be effectively prevented. Strengthening daily maintenance, optimizing operational management, and ensuring proper operation protocols can extend the lifespan of the generator set, enhance its stability and safety, and ensure smooth and uninterrupted production operations.