Forced Oil Circulation Air Cooler For Substation Main Transformer
Forced Oil Circulation Air Cooler for Substation Main Transformer
The forced oil circulation air cooler for substation main transformers is a crucial component for ensuring the safe and stable operation of transformers.
Working Principle
The forced oil circulation air - cooling system utilizes an external oil pump to make the transformer insulating oil circulate back and forth between the transformer body and the cooler with a fan. The transformer oil absorbs the heat generated by the core and windings during operation. Driven by the oil pump, the hot oil enters the cooler, transfers heat to the cooling tubes, and the heat on the surface of the finned tubes is taken away by the air flow under the forced action of the fan, thus achieving the purpose of cooling the transformer oil. The cooled oil returns to the transformer body to continue absorbing heat, forming a closed - loop cooling system.
Structural Composition
Heat Exchanger: It is usually a finned - tube heat exchanger. The heat exchanger has multiple loops, and there are partitions welded in the oil collecting chamber to form an oil - circulation loop. The metal tubes of the heat exchanger are equipped with spiral - shaped fins to increase the heat - exchange area.
Submersible Oil Pump: Installed at the bottom of the heat exchanger, it is the core power component that forces the extraction of hot oil from the bottom of the transformer tank (or from the upper part of the tank according to the design) and sends it to the cooler to provide power for oil circulation.
Cooling Fan: Installed outside the heat exchanger, it is usually an axial - flow fan. By forcing the inhalation of cold air and high - speed blowing through the fin surface, it exchanges heat with the hot oil in the tube bundle to take away the heat.
Oil Flow Relay: Installed on the connecting pipe at the oil outlet end of the submersible oil pump, it monitors the state of oil circulation. If the oil pump fails or the oil flow is interrupted due to blockage, it will send out a signal and trigger the protection mechanism.
Control System: It includes a total control box and sub - control boxes. The total control box contains main contactors, control switches, relays, etc.; the sub - control boxes are installed below each cooler and mainly contain contactors and thermal relays. The control system realizes functions such as the temperature - controlled switching on and off of coolers, and cooperates with the non - electrical protection of transformers to achieve over - temperature tripping.
Control Principle
Power Supply Automatic Switching: The cooling system of forced - oil - circulation transformers usually has two - way power supplies. When the working power supply fails, the standby power supply automatically switches on; when the working power supply is restored, the standby power supply automatically switches off.
Cooler Control: When the transformer is put into operation, the cooler is automatically put into operation; when the transformer is withdrawn from operation, all coolers are automatically cut off. When the upper - layer oil temperature or winding temperature of the transformer reaches a certain value, the auxiliary cooler that has not been put into operation is automatically started; when the running auxiliary cooler fails, the standby cooler is automatically started.
Cooler Full - Stop Tripping: When the cooler is fully stopped, if the main transformer oil temperature reaches or exceeds 75°C, the main transformer trips after 20 minutes; if the main transformer oil temperature is lower than 75°C, the main transformer can continue to operate until the upper - layer oil temperature reaches 75°C, but the operation time does not exceed 60 minutes.
Application Scenarios
It is mainly applicable to 220kV and above transformers. Because in high - voltage and large - capacity transformers, a large amount of heat is generated during operation, and the heat - dissipation efficiency of natural cooling or ordinary air - cooling cannot meet the requirements. The forced - oil - circulation air - cooling method has a high heat - dissipation efficiency and can effectively ensure the normal operation temperature of transformers.
