Overload capacity and time of transformer_ Analysis of overl

This paper mainly introduces the overload of transformer. Firstly, it introduces what condition of transformer is called overload. Secondly, it describes the main reason of transformer overload and the overload capacity and time of transformer. Finally, it introduces the overload capacity analysis of dichloro dry-type transformer. Let's understand it with the editor.

 

 

 

What is the condition of transformer called overload

 

Transformers have their own fixed capacity, when the power load exceeds the capacity, that is overload.

 

 

 

If the capacity of transformer is fixed and the voltage of primary side and secondary side is also fixed, then the rated current of primary side and secondary side is the maximum current that the transformer can carry. With the increase of load, the current of primary side and secondary side will increase correspondingly. When the current exceeds the rated current, it is overload.

 

 

 

For example: a 10kV / 400V transformer, the capacity is 1000KVA, its primary side and secondary side rated current are 58a and 1440a respectively

 

 

 

When the secondary current exceeds 1440, the primary current must also exceed 58. It's overloaded.

 

① The main feature of mechanical overload is that the motor is hot, and the running current can be read from the display screen.

 

 

 

② The unbalanced three-phase voltage causes excessive operating current of a certain phase, which leads to overload trip. Its characteristic is that the motor heating is unbalanced, and it may not be found when reading the operating current from the display screen (because the display screen only displays one phase current).

 

 

 

③ The internal current detection part of the maloperation inverter fails, and the detected current signal is too large, resulting in tripping.

 

 

 

Overload capacity and time of transformer

 

 

The overload capacity of dry-type transformer is related to the ambient temperature, the load before overload (initial load), insulation and heat dissipation of transformer and heating time constant. If necessary, the overload curve of dry transformer can be obtained from the manufacturer.

 

 

 

At present, the annual output of resin insulated dry-type transformer in China has reached 10000mva, which has become one of the largest dry-type transformer production and sales in the world. With the popularization and application of SC (b) 9 series with low noise (noise of distribution transformer under 2500kVA has been controlled within 50dB) and energy saving (no-load loss reduced by 25%), the performance index and manufacturing technology of dry-type transformer in China have reached the world advanced level.

 

 

 

With the popularization and application of dry-type transformer, its manufacturing technology has also obtained great development, which can be predicted that the future dry-type transformer will be further developed in the following aspects.

 

 

 

(1) Energy saving and low noise: with the introduction of new materials, new technologies and technologies such as new low consumption silicon steel sheet, foil winding structure, step core joint, environmental protection requirements, noise research, and computer optimization design, the future dry-type transformer will be more energy-saving and more quiet.

 

 

 

(2) High reliability: to improve the quality and reliability of products will be the unremitting pursuit of people.

 

 

 

(3) Environmental protection characteristic certification: Based on the European standard HD464, the research and certification of the climatic resistance (CO, C1, C2), environmental resistance (E0, E1, E2) and fire resistance (F0, F1, F2) characteristics of dry-type transformers are carried out.

 

 

 

(4) Large capacity: from dry type transformer mainly distributed from 50-2500kva to 10000-20000kva / 35kV Power transformer, with the increasing of urban power load, the urban network regional substation is becoming more and more in the load center of urban center, residential district, large-scale factory and mine, and the 35kV large-capacity central power transformer will be widely used.

 

 

 

(5) Multi function combination: from single transformer to multi-function combination transformer with air cooling, protection shell, temperature computer interface, zero sequence transformer, power metering, closed bus and side outgoing line.

 

 

 

(6) Multi field development: from distribution transformer as the main, it develops into special transformers and multi-purpose fields, such as station transformer, excitation transformer, metro traction rectifier transformer, high current electric furnace transformer, nuclear power station, marine and oil production platform. Among them, the dry-type traction transformer for urban subway and rail transit has three levels of voltage of 10, 20 and 35kV, with capacity of 800, 2500 and 3300kva. In order to reduce harmonic pollution, it has developed from 12 pulse rectification.