Power transformer is mainly realized by power electronics technology, its basic principle is in the original power frequency signal through the power electronics circuit into high frequency signal, namely frequency rise, and then through the middle high frequency isolation transformer coupling to the vice side, and then restored into power frequency signal, namely frequency fall. By adopting appropriate control scheme to control the work of power electronic devices, the electric energy of one frequency, voltage and waveform can be transformed into the electric energy of another frequency, voltage and waveform. Because the volume of the isolated transformer in the middle depends on the saturation flux density of the core material and the maximum allowable temperature rise of the core and winding, and the saturation flux density is inversely proportional to the working frequency, so that improving the working frequency can improve the utilization rate of the core, thereby reducing the volume of the transformer and improving its overall efficiency.
One, Measures to improve the short circuit resistance of power transformers
The safe, economical and reliable operation and output of transformer depend on its manufacturing quality, operating environment and maintenance quality. This chapter tries to answer the effective measures to prevent transformer sudden failure in the process of transformer operation and maintenance.Power grid often due to lightning strike, relay protection misoperation or rejection caused by short circuit, the strong impact of short circuit current may cause transformer damage, so from all aspects of efforts to improve the transformer short circuit tolerance ability. The statistical results of transformer short-circuit impact accidents show that manufacturing causes account for about 80%, while operation and maintenance causes only account for about 10%. The measures related to design and manufacturing have been discussed in the second chapter. This chapter focuses on the measures to be taken in the process of operation and maintenance. In the process of operation and maintenance, on the one hand, short-circuit faults should be minimized to reduce the number of shocks to the transformer; On the other hand, the deformation of transformer windings should be tested in time to prevent them from happening.
(1) Standard design, pay attention to the axial compression process of coil manufacturing.
(2) Short circuit test of transformer to prevent it from happening.
(3) Use reliable relay protection and automatic reclosing system.
(4) Actively carry out transformer winding deformation test and diagnosis.
(5) Strengthen the inspection in site construction and operation and maintenance, and use reliable short-circuit protection system
Ability to withstand all kinds of short circuit current depends mainly on transformer structure design and manufacturing process, and operation management, operation conditions and the construction technology level has a lot to do, transformer short circuit accident great harm to the operation of the grid system, to avoid the happening of the accident, should from many aspects to take effective control measures, To ensure the safe and stable operation of transformer and power grid system.