Oil-immersed power transformers are indispensable key devices in power systems and are widely used in power generation, transmission, and distribution. They achieve voltage transformation through the principle of electromagnetic induction to meet different power needs. This article will provide a detailed introduction to the working principle, structural composition, advantages, and application scenarios of oil-immersed power transformers, helping readers gain a comprehensive understanding of this important power equipment.
Basic Working Principle of Oil-Immersed Power Transformers
Oil-immersed power transformers work based on the principle of electromagnetic induction and mainly consist of a core, windings (primary and secondary), insulating oil, and a cooling system. Their core function is to change the alternating current (AC) voltage through electromagnetic induction while keeping the power essentially constant (neglecting losses).
1. Electromagnetic Induction Process
When alternating current (AC) flows through the primary winding, it generates a varying magnetic field in the core. This changing magnetic field induces an electromotive force (voltage) in the secondary winding, thereby achieving voltage step-up or step-down.
If the secondary winding has more turns than the primary winding, the output voltage is increased (step-up transformer).
Conversely, if the secondary winding has fewer turns than the primary winding, the output voltage is decreased (step-down transformer).
2. Role of Insulating Oil
The windings and core of an oil-immersed transformer are submerged in transformer oil, which serves several key functions:
Insulation: The oil has a high dielectric strength, effectively preventing short circuits between windings or between the windings and the core.
Cooling: During operation, the transformer generates heat. The oil dissipates heat through natural convection or forced circulation, maintaining stable equipment temperature.
Arc Quenching: In the event of an arc inside the transformer, the oil can quickly cool and suppress the arc expansion, enhancing safety.
Structural Composition of Oil-Immersed Power Transformers
The core structure of an oil-immersed power transformer includes the following components:
1. Core
Made of high-permeability silicon steel laminations, the core forms a low-magnetic-reluctance path to enhance magnetic field coupling efficiency and reduce eddy current losses.
2. Windings (Coils)
Primary Winding: Connected to the input power source to receive electrical energy.
Secondary Winding: Outputs the transformed voltage for use by the load.
The windings are typically made of copper or aluminum conductors and are insulated with multiple layers to prevent short circuits.
3. Tank and Insulating Oil
Tank: Fabricated from steel plates and filled with transformer oil to protect internal components.
Insulating Oil: Generally mineral oil or synthetic ester oil is used, and its insulating properties and chemical stability need to be regularly tested.
4. Cooling System
Common cooling methods include:
Natural Oil Cooling (ONAN): Relying on natural convection of the oil for heat dissipation.
Forced Air Cooling (ONAF): Equipped with fans to enhance cooling.
Forced Oil Circulation Cooling (OFAF/ODAF): Using oil pumps to accelerate oil circulation and improve cooling efficiency.
5. Protective Devices
Oil Level Indicator: Monitors the oil level to prevent low oil levels from affecting cooling and insulation.
Pressure Relief Valve: Automatically releases pressure when the internal pressure is too high to prevent explosion.
Gas Relay (Buchholz Relay): Detects gases generated by internal faults to trigger alarms or tripping.
Advantages of Oil-Immersed Power Transformers
Compared to dry-type transformers, oil-immersed transformers have the following advantages:
1. Good Heat Dissipation: The high specific heat capacity and fluidity of oil effectively remove heat, making them suitable for large-capacity transformers.
2. High Insulation Strength: The dielectric strength of oil is much higher than that of air, allowing it to withstand higher voltage levels.
3. Long Service Life: Good heat dissipation and insulation properties extend the service life of the equipment.
4. Lower Cost: In high-voltage, large-capacity applications, oil-immersed transformers are more economical than dry-type transformers.
Application Scenarios of Oil-Immersed Power Transformers
Oil-immersed transformers are widely used in:
- Power Systems: Voltage step-up in power plants, voltage step-down in substations, and long-distance power transmission.
- Industrial Fields: High-power electrical equipment in steel, chemical, and mining industries.
- Renewable Energy: Grid-connected transformers in wind farms and photovoltaic power stations.
- Urban Power Distribution: 10kV/0.4kV distribution transformers for residential and commercial power supply.
Oil-immersed power transformers achieve voltage transformation through electromagnetic induction, with their core advantages lying in efficient insulation and heat dissipation capabilities, making them suitable for high-voltage, high-power power systems. As the power industry develops, oil-immersed transformers are continuously optimized in terms of reliability, energy efficiency, and intelligence, and they will remain a core device for power transmission and distribution in the future.
If you need high-quality oil-immersed transformers, it is recommended to choose professional manufacturers to ensure that the equipment meets international standards (such as IEC, GB), and regular maintenance and testing should be carried out to ensure long-term stable operation.
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