What is an oil immersed transformer? Application and principle of oil immersed transformer
Application of Oil Immersed Transformers
Oil immersed transformers are used in various applications and fields. The main application is power transmission and distribution. The electricity generated by power plants is usually high voltage.
The electricity is supported by steel towers and sent to transmission lines. By using oil immersed transformers, this high-voltage power can be converted and supplied to low-voltage distribution lines.
Then the low-voltage power is transmitted to places with demand, such as ordinary households, factories, and commercial facilities. The demand location also uses oil immersed transformers to convert the voltage into a voltage level suitable for the demand. In general households, voltages such as 100V AC or 200V AC are used, while in factories and commercial facilities, 200V AC or 400V AC can be used.
Principle of oil immersed transformer
Oil immersed transformers are composed of iron cores, coils, oil tanks, insulating oil, etc.
1. Iron core
The center of the transformer is the iron core. The iron core is made of laminated silicon steel plates, forming a magnetic circuit. The laminated structure minimizes magnetic losses and achieves efficient power conversion.
2. Coil
There are windings around the iron core, one on the high voltage side and one on the low voltage side. They are made of copper or aluminum wire and generate a magnetic field when current flows through them. In a typical step-down transformer, there are fewer turns on the high-voltage side winding and more turns on the low-voltage side winding.
3. Fuel tank
These components are installed in steel tanks. The oil tank is filled with insulating oil to protect the transformer structure and insulate its interior. Fuel tanks usually have fins to help circulate cooling oil and dissipate heat.
4. Insulating oil
Mineral oil is widely used as insulating oil. In recent years, environmentally friendly products such as transformers using sunflower seed oil or rapeseed oil have emerged. Although expensive, it can prevent environmental pollution caused by leakage accidents.
In addition, by analyzing the concentration of organic gases in the insulating oil, the degradation status of the transformer can be monitored. When the transformer overheats, ethylene and ethane are produced, and partial discharge produces acetylene and hydrogen gas. Acetylene is an organic gas that cannot be detected even in trace amounts because it is a gas caused by internal abnormalities in transformers.
Types of oil immersed transformers
Oil immersed transformers are divided into self cooling and forced cooling types.
1. Self cooling type
Self cooling transformers are transformers that use internal oil and cooling devices for natural cooling. Heat is dissipated through radiators installed inside water tanks, etc. Oil filled self cooling transformer is the most common form of transformer, widely used in power transmission and distribution systems.
2. Forced cooling type
The forced cooling type is a transformer that uses a cooling device to forcibly circulate oil. Forced circulation can enhance the cooling effect. Oil is usually circulated through a pump or fan to make it suitable for use in high load and high temperature environments.
Other information about oil immersed transformers
1. Allowable temperature for oil immersed transformers
If an oil immersed transformer overheats, there is a risk of insulation failure due to forced deterioration of the insulation oil. In the worst-case scenario, there is also a risk of fire. Therefore, maintaining the working temperature below the allowable value is an important management project.
The maximum allowable temperature for commonly used oil immersed transformers is 105 ℃. But due to the influence of external temperature and temperature difference, it is kept at around 95 ℃ or below.
2. Treatment of oil immersed transformers under the Fire Protection Law
The mineral oil used in oil immersed transformers is generally grade 3 petroleum. The insulation oil inside large oil immersed transformers exceeds 2000 liters, so if it is only oil, it belongs to the category of dangerous goods stipulated by the Fire Protection Law. However, when a transformer is connected to a circuit, it is regulated by the Electricity Commercial Law and is no longer considered a hazardous substance.
If the old transformer is dismantled and disconnected from the circuit, it will be considered a hazardous material. Specifically, there are multiple possible scenarios, so it is necessary to confirm with the fire department and take appropriate action.