We cannot live without the use of electricity. Then, in the process of power transmission, transformation and distribution of power system, transformer is an important electrical equipment. Transformers can be seen everywhere in industrial enterprises, shopping malls, office buildings and residential areas. Transformers play an extremely important role in the power industry. As a power practitioner, you must understand the knowledge about transformers. Here are two general knowledge about transformers I summarized for you. After reading, you will have a new understanding of transformers.

 

Principle of transformer

Transformer is a device that uses the principle of electromagnetic induction to change AC voltage and current. The main components are primary coil, secondary coil and iron core (magnetic core). The following figure shows several transformers with different shapes

 

What are the functions of transformers?

 Voltage change: increase or decrease the voltage, and change the voltage into the voltage level used by residents or industry through the process of boosting, conveying and reducing voltage before the generator is found.

Variable current: change the current while changing the voltage

 Isolation: isolate the user system from the power supply system to narrow the scope of the accident.

 

What types of power transformers are there?

 Oil immersed transformer: transformer with transformer oil as insulation medium and cooling medium. All iron cores and coils are immersed in insulating oil.

 Dry type transformer: the iron core and coil are cast with epoxy resin material to play the role of insulation.

 Amorphous alloy transformer: the new transformer developed this year adopts amorphous alloy material as the insulation medium, with good temperature resistance.

 

What are the components of the transformer?

 Body body: including iron core, winding and insulation support

 Voltage regulating device: tap changer, (on load voltage regulating device and non excitation voltage regulating device)

 Oil tank, fin radiator (wing), sleeve

 Temperature measuring devices: oil, gas filter, etc.

 

Transformer oil action

 Insulation function: transformer oil has strong insulation performance, which will produce insulation strength between winding and shell. Common types are db5 and db45.

Heat dissipation: according to the principle of heating rise, the transformer oil circulates naturally between the body and the sheet radiator, and dissipates the heat through the radiator to keep the temperature of the coil not too high.

 Arc suppression: when operating the on load voltage regulating device, the tap changer will produce arc light when it is opened, and the transformer oil can extinguish the arc light and play a protective role.

 

What is the function of oil conservator (conservator)?

The conservator (oil conservator) is installed on the inclined upper part of the oil tank, and an oil pipe is connected with the oil tank. When the volume of transformer oil expands and contracts with the change of oil temperature, the conservator plays the role of oil storage and replenishment. Prevent oil from being oxidized and affected with moisture due to contact with air. The conservator is equipped with an oil standard pipe, and some are also equipped with a liquid level indicator to observe the change of oil level.

 

What is on load voltage regulation?

 On load voltage regulation is a voltage regulation method in which the transformer can change the voltage by changing the tap gear when it is operating under load

 

 What are the losses of transformer in operation?

 Transformer losses include: no-load loss (iron loss): loss caused by iron core eddy current,

 Load loss (copper loss): the loss caused by the resistance heating of the winding.

 

Representation of transformer model:

Basic model: S

Design serial number or performance level code: 11

Rated capacity: 500KVA

High voltage side voltage: 10KV

 

Main technical data on nameplate

Transformer primary and secondary rated voltage, rated capacity, wiring group, primary and secondary rated current, variable impedance voltage, tap changer adjustment voltage range, service environmental conditions, transformer oil model and weight, etc.

 

Function of moisture absorber (respirator)

Since the temperature of the transformer will change at any time during operation, resulting in the increase or decrease of the oil level inside the transformer, the gas must be discharged, otherwise the pressure will rise; It can be understood as the annual process of breathing, which plays a role in preventing the deterioration of direct contact between oil and air.

A silica gel tank is installed on the exhalation channel of the oil. The transformer breathes through the silica gel, and the discharged water is absorbed. When the water reaches a certain degree, the color of the silica gel will change from blue to red. At this time, the silica gel needs to be replaced. As shown in the figure

 

What is a gas relay? What is the function?

Gas relay (also known as gas relay) is a protective device used by the transformer. It is installed in the pipeline between the oil conservator and the oil tank of the transformer. When the internal fault of the transformer decomposes the oil to produce gas or causes oil flow surge, the contact of the gas relay acts, and sends "heavy gas' trip signal and" light gas "alarm signal to the personnel on duty through the internal electrical normally open contact, Remind that the transformer is abnormal or faulty.