Study On Transformer Fault Real-time Digital Simulation And Closed-loop Test

Relay protection has been greatly promoted by its close-loop testing technique. Transformer protection is a kind of computer protection with the minimum rate of right motion, while issue of inrush current is the core of transformer protection. Therefore, the current research is of vital theoretical and applied importance to the development of real-time close-loop testing of the transformer protected non-linear inrush current.After analyzing the internal fault of transformer and the emulation of the inrush current, this paper adopts the liner model to build the non-linear transient model of it. Basing on this model, we have developed the real-time emulation testing system of the transformer's transient fault.The portable emulation testing device is based on Ethernet Communication. It is connected by emulation device, computer transformer protection device and emulated breaker to conduct the current testing. The hardware circuit of protection testing system under study is composed of three units; those are man-machine interface unit, digital to analog converter unit, and power amplifier and feedback unit. The composition of these three units is capable of closed-loop and automatic testing. Having transformed the emulated waveform data, hardware card sends the emulated signal to protection device, and determine the current state of its operation, whether analog circuit breaker is switched on and so on. Then the state will be sent back to the server computer emulation software through hardware board.This paper develops the real-time emulation software based on the transformer faults of PC and inrush current. By configuring the basic parameter of transformer and emulated faults into the transient calculation model, this software relies on various faults to realize such functions as storage and wave display of emulated data.Emulated data will be sent to the PC protection device under testing through portable emulation device. At the same time it inspects motion of the protection device and the position of power switch of the emulated breaker, and then feedbacks it to the model to realize close-loop emulation after protection device'motion. In terms of function, the testing software can be divided into five parts: settling protection testing condition and parameter, preparing data, emulation testing, outputting the test result and repainting the emulated wave. Modular programming makes this program clearer and simpler.In this test, the various emulated fault waveform data can all ensure the proper function of the protection device so as to verify the accuracy of the emulation test. Combined with the transformer transient model, this emulation testing system has made obvious improvement in terms of speed and accuracy compared to previous systems.