What factors affect the operational stability of transformers?

The operational stability of transformers is affected by multiple factors, involving various aspects such as design, manufacturing, operating environment, and maintenance management. The following is a detailed analysis from both internal and external factors:

1. Internal Factors

① Design Rationality

Winding structure: The number of turns, arrangement, and insulation design of the windings directly affect the electrical performance and short-circuit resistance of the transformer. For example, using a tangled or continuous winding structure can improve the ability to withstand impulse voltage.

Core materials and process: The material of the core (such as silicon steel sheets), lamination thickness, and joint method affect hysteresis loss and eddy current loss. High-permeability, low-loss core materials can improve efficiency and reduce heat generation.

Cooling system design: The oil channel design and radiator layout of oil-immersed transformers, and the air duct design of dry-type transformers, directly affect the heat dissipation effect. Insufficient heat dissipation can lead to local overheating and accelerate insulation aging.

② Manufacturing Quality

Winding winding process: Improper winding tightness and interlayer insulation treatment may lead to inter-turn short circuits or partial discharge.

Core assembly accuracy: Loose core joints and burrs on silicon steel sheets can increase magnetic resistance, increasing no-load loss and noise.

Insulation material quality: The quality of insulation paper, insulating oil, and other materials directly affects the insulation performance of the transformer. Inferior insulation materials are prone to aging and breakdown, leading to failures.

③ Component Reliability

Tap changer: Poor contact or jamming of the tap changer operating mechanism can lead to voltage regulation failure or local overheating.

Bushings: Poor sealing or insulation aging of bushings may lead to oil leakage or flashover.

Protective devices such as thermometers and pressure relief valves: Malfunctioning protective devices can lead to the expansion of faults; for example, failure to alarm at excessively high temperatures may cause winding burnout.

2. External Factors

① Load Conditions

Load rate: Long-term overload operation will cause the winding temperature to rise, accelerating insulation aging and shortening the transformer’s lifespan.

Load fluctuations: Frequent load changes (such as impact loads) will generate mechanical and thermal stress, leading to winding loosening or insulation damage. Three-phase imbalance: Unbalanced three-phase loads can cause neutral point shift, increase zero-sequence current, and lead to local overheating or vibration.

② Operating Environment

Temperature: High ambient temperature reduces heat dissipation efficiency, leading to excessive transformer temperature rise. High temperatures also accelerate the aging of insulation materials.

Humidity: High humidity environments can cause insulation to become damp, reducing insulation resistance and leading to flashover or breakdown.

Altitude: In high-altitude areas, the air is thinner, resulting in poorer heat dissipation.  Derating or enhanced cooling is required.

Pollution: Dust, salt spray, and other pollutants can adhere to the insulation surface, reducing insulation performance and increasing the risk of creepage.

③ Power Quality

Voltage fluctuations: High voltage can lead to core saturation, increasing no-load losses and noise; low voltage can increase current and copper losses.

Frequency fluctuations: Frequency deviations from the rated value affect the transformer’s excitation current and losses, and prolonged operation may lead to overheating.

Harmonics: Harmonics generated by nonlinear loads increase transformer losses, leading to local overheating and increased vibration.

④ Maintenance and Management

Regular maintenance: Failure to perform regular maintenance such as insulation testing and oil analysis (for oil-immersed transformers) may prevent timely detection of potential faults.

Cooling system maintenance: Blocked radiators, fan failures, etc., can lead to poor heat dissipation and overheating.

Operating procedures: Improper operations such as on-load tap changer operation and failure to inspect after short-circuit impacts can damage the transformer.

⑤ External Interference

Short-circuit impact: The huge current generated by system short circuits can cause winding deformation and insulation damage.

Lightning overvoltage: Lightning surges can break down transformer insulation, especially bushings and incoming terminals.

Mechanical vibration: Vibration from nearby equipment or foundation settlement can cause internal components of the transformer to loosen, leading to malfunctions.

3. Specific Manifestations of Key Influencing Factors

① Insulation Aging

Cause: Long-term high temperature, electric field stress, and mechanical stress lead to a decrease in the performance of insulation materials.

Impact: Reduced insulation resistance, increased partial discharge, ultimately leading to breakdown or short circuit.

② Winding Deformation

Cause: Short-circuit impacts and transportation collisions cause axial or radial displacement of the windings. Effects: Inter-turn short circuits, insulation damage, and even transformer failure.

③ Oil deterioration (oil-immersed transformers)

Causes: High temperature, oxidation, and moisture ingress lead to increased oil acidity and decreased breakdown voltage.

Effects: Reduced heat dissipation efficiency, decreased insulation performance, and potential arc faults.

④ Over-excitation

Causes: Excessive voltage or low frequency leading to core saturation.

Effects: A sharp increase in excitation current, core heating, and potential insulation damage.

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