1. Classification and models of power transformers
2. 1. Classification by use
3. (1) Step-up transformer: used by the power plant to transmit electricity to the outside.
4. (2) Step-down transformer: The substation of the power supply bureau is used for voltage conversion.
5. (3) Distribution transformer: used to supply power to users.
6. (4) Plant transformer: Provides internal electricity for the power plant.
7. (5) Transformer for station: Provide internal electricity for the substation.
8. (6) Converter transformer: for DC power transmission, one side is connected to AC power, and one side is connected to the converter valve.
9. (7) Rectifier transformer: used in thermal power plants to supply power to electrostatic precipitators.

This article mainly counts 7 types of fault judgment methods and solution analysis of dry-type transformer noise. If there is any error or omission, please point it out in the comment area.
Analysis of 7 types of fault judgment methods and solutions for dry-type transformer noise
➢Resonance problems of fans, casings and other components
➢Installation problems
➢Influence of installation environment
➢The problem of vibration of busbar bridge
➢Transformer core resonates by itself.
➢Transformer coil self-resonance
➢The problem of the nature of the load

Corresponding protection devices shall be installed for the short-circuit faults of the transformer lead wires, bushings and internals, and shall meet the following requirements: 
1) The single-running transformer of 10MVA and above and the parallel running transformer of 6.3MVA and above should be equipped with longitudinal differential protection. Important transformers with 6.3MVA and below operating independently can also be equipped with longitudinal differential protection.
2) Transformers below 10MVA can be equipped with current quick-break protection and overcurrent protection. For transformers of 2MVA and above, when the current quick-break sensitivity coefficient does not meet the requirements, longitudinal differential protection should be installed. 
3) 0.4MVA and above, the primary voltage is 10kV and below, and the coil is a transformer with a delta-star connection, and a two-phase three-relay type overcurrent protection can be used.
4) The various protection devices specified in this article shall operate to disconnect the circuit breakers on each side of the transformer.

01 Inrush current
When a transformer is first energized, a phenomenon called magnetizing inrush occurs. Although inrush currents are generally not as disruptive as fault currents, the duration of magnetizing inrush currents is on the order of seconds (compared to periods with fault currents).

No-load test: Apply the rated voltage of the sine wave rated frequency from a certain winding of the transformer (generally from the secondary low-voltage side), and open the other windings to measure the no-load current and no-load loss. If the test conditions are limited and the power supply voltage cannot reach the rated voltage, the test can be performed under non-rated voltage conditions. This test method has a large error and is generally only used to check whether the transformer is faulty. Only the test voltage reaches more than 80% of the rated voltage. can be used to test the no-load loss.

Oil-immersed transformers have the characteristics of good heat dissipation, low loss, large capacity and low price. At present, most of the power transformers running on the grid are oil-immersed transformers, of which more than 80% are cooled by natural oil circulation. It is a commonly used cooling structure to set a guide plate in the coil of a natural oil circulation transformer. This paper focuses on analyzing the structure, operation and maintenance of oil-immersed power transformers, and specifically analyzes the oil system of oil-immersed power transformers, and briefly analyzes the faults of oil-immersed power transformers. Hope to increase understanding and analysis of my country's oil-immersed power transformers.

Introduction
transformer
A device that changes voltage, current, or phase by coupling a magnetic circuit
Why learn Transformers?
Transformers are also known as stationary AC motors

This video showed you what a main power transformer look like.

The transformer is a static device in continuous operation, which is relatively reliable in operation and has less chance of failure. However, since most of the transformers are installed outdoors, and are affected by the load during operation and the short-circuit fault of the power system, various faults and abnormal situations inevitably occur during operation.

The cooling system of the power transformer consists of two parts: the internal cooling system, which ensures that the heat of the winding and the iron core is dissipated into the surrounding medium; the external cooling system, which ensures that the heat in the medium is dissipated to the outside of the transformer. According to the size of the transformer capacity, the medium and the type of circulation, the transformer adopts different cooling methods.

The grounding transformer is referred to as grounding transformer for short. According to the filling medium, the grounding transformer can be divided into oil type and dry type; According to the number of phases, the grounding transformer can be divided into three-phase grounding transformer and single-phase grounding transformer. The function of the grounding transformer is to provide an artificial neutral point for the system with ungrounded neutral point, which is convenient for the use of arc suppression coil or small resistance grounding mode, so as to reduce the capacitance current to ground in case of grounding short circuit fault in the distribution network and improve the power supply reliability of the distribution system.

Analysis of abnormal operation of transformers
Transformer sound is abnormal


As soon as the transformer is connected to the power supply, there will be a buzzing sound, which is mainly due to the effect of high-voltage magnetic flux. During normal operation, the sound of the transformer is uniform. When there are other noises, you should carefully find the cause and deal with it.