General Requirements for Power Transformer Cooling Devices
a. Install all cooling devices according to the manufacturer's regulations;
b. The cooling system with strong oil circulation must have two independent working power sources and be able to switch automatically.When the working power supply fails, it should automatically switch on the backup power supply and send out sound and light signals;
c. Strong oil circulation transformer, when the faulty cooler is removed, it should send out sound and light signals, and automatically (water-cooled can be manually) put into the spare cooler;
d. The auxiliary motors of fans, water pumps and oil pumps should be protected against overload, short circuit and phase failure; there should be a device for monitoring the rotation direction of the oil pump motor;
e. The oil pump of the water cooler should be installed on the oil inlet side of the cooler, and ensure that the oil pressure in the cooler is about 0.05MPa higher than the water pressure under any circumstances (unless otherwise specified by the manufacturer).There should be a drain cock on the water outlet side of the cooler;
f. For transformers cooled by strong oil circulating water, check valves shall be installed at the outlets of submersible pumps of each cooler;
g. For the transformer cooled by strong oil circulation, it should be able to control the switching of the cooler according to the temperature and (or) load.
The Role of the Transformer Cooler
When there is a temperature difference between the upper oil temperature of the transformer and the lower oil temperature, the oil temperature convection will be formed through the cooler, and after being cooled by the cooler, it will flow back to the oil tank to reduce the temperature of the transformer.
Cooling method of transformer cooler
Oil-immersed natural air cooling method;
Oil-immersed air-cooled type;
Forced oil circulation water cooling;
Forced oil circulation air-cooled type;
Forced oil circulation guide cooling method.
In the 500kV substation, the general large-scale transformer adopts the forced oil circulation air-cooled type, while the ultra-large transformer adopts the forced oil circulation oriented cooling method.
How transformer coolers work
Traditional power transformers are manually controlled fans, and each transformer has 6 groups of air-cooled motors that need to be controlled, and each group of fans is realized by relying on thermal relays.The circuit of the fan power supply Controlled by the contactor, the fan measures the oil temperature of the transformer and the overload process of the transformer, so as to determine the start and stop of the fan through logical judgment.
The mechanical contacts are mainly driven by artificial mechanical contacts.Such traditional control can only be controlled manually.But its biggest disadvantage is that all the fans have to start and stop at the same time, and the inrush current generated by it is relatively large when it starts, which often causes damage to the components in the circuit.When its temperature is between 45 and 55 When the temperature is 100°C, it is often adopted the method of putting in all the work, which will bring about a huge waste of energy and also cause great difficulties to the maintenance of the equipment.
The main components used in the general cooling control system include relays, thermal relays, and various contact logic circuit control systems.The control logic is very complicated.In the actual process of operation, the contactor will contact the contact many times.Burning phenomenon caused by separation and separation.And the fan also lacks some very necessary protections, such as overload, phase loss and overload, etc., which will reduce the reliability of its operation and virtually increase the cost of operation in the actual operation process.
Components of strong oil and strong air-cooled transformer cooler
The cooler is composed of heat exchanger, fan, motor, air passage, oil pump oil flow indicator, etc.The cooling fan is used to expel the hot air emitted from the heat exchanger.The oil pump is installed in the lower part of the cooler to circulate the top oil of the heat exchanger to the lower part.The oil flow indicator is installed at a more obvious position on the lower part of the cooler, so that the operating personnel can observe the operation status of the oil pump.
The role of the oil tank and cooling device of the transformer
The oil tank of the transformer is the shell of the transformer, which contains the iron core, windings and transformer oil, and also plays a certain role in heat dissipation.
The function of the transformer cooling device is that when there is a temperature difference in the upper oil temperature of the transformer, the oil circulation is formed through the radiator, so that the oil flows back to the oil tank after being cooled by the radiator, which has the effect of reducing the temperature of the transformer oil.In order to improve the cooling effect, measures such as air cooling, strong oil air cooling or strong oil water cooling can be adopted.
