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).

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.

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.

The parallel operation of transformers means that the primary windings of two or more transformers are connected in parallel on the busbar of the same voltage, and the secondary windings are connected in parallel on the busbar of another voltage.






Its meaning is: when one transformer fails, other transformers running in parallel can still continue to operate to ensure the power consumption of important users; or when the transformer needs to be repaired, the standby transformer can be connected in parallel, and then the transformer to be repaired is powered off and repaired. , which can not only ensure the planned maintenance of the transformer, but also ensure that the power supply is not interrupted and improve the reliability of the power supply.

There are two main causes of transformer oil leakage: on the one hand, problems left over in the process of transformer design and manufacturing process; On the other hand, leakage is caused by improper installation and maintenance of transformer. The main leakage parts of the transformer often appear at the radiator interface, flat butterfly valve cap, sleeve, porcelain bottle, weld, sand hole, flange and other parts.

Gas protection is the main protection for transformer internal faults. It can act sensitively to transformer inter-turn and inter-layer short circuits, iron core faults, internal bushing faults, internal winding disconnection, insulation deterioration and oil level drop. When a fault occurs inside the oil-immersed transformer, the arc will decompose the insulating material and generate a large amount of gas, which flows from the oil tank to the oil pillow, and its intensity varies with the severity of the fault, reflecting the air flow and oil flow The action protection is called gas protection, also called gas protection. During the operation of the transformer, due to internal faults, sometimes we cannot identify and take measures in time, which is easy to cause some accidents. After the protection of the gas relay, the occurrence of similar incidents can be avoided to a certain extent.