Study On Inrush Restraining Technology Of Energizing No-load Transformer

Excitation inrush current can reach 6 to 8 times of the rated current when power transformer no-load closing, it has a great impact on the grid, and affect other electrical equipment directly, especially power electronics and other sensitive electronic devices, also make differential protection malfunction. And it would damage the insulation of the transformer itself, also affect the life of the transformer. Therefore, inhibition excitation inrush current of the transformer no-load switching has important economic value. For this purpose, soft-start for transformer was studied in this thesis.Firstly, development at home and abroad and prospects of the inhibition of the transformer excitation inrush current no-load switching technology are described in the thesis. Have a theoretical analysis of no-load starting process of the transformer. Based on the comprehensive comparison of different start and then soft-start method is proposed. And its working principle and design of main circuit are described detail.Secondly, hardware circuit design of the soft starter is introduced, including analysis and design of the main circuit used PIC16F873 as the core, the thyristor drive circuit, power circuit, phase sequence detection circuit and RS232 communication circuit. And software design of control system are introduced, including the system main program, phase sequence detection subroutine, the phase angle calculation routine, the trigger signal interrupt subroutine, and RS232communication procedures. And some flow charts of the software module program are given.Finally, having an experiment, through the experimental debugging, verify the correctness and feasibility of hardware circuit design. It achieved the desired results basically.