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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