The Research Of Signal Reversion And Technique Of Measuring And Testing On The Electric Transformer

Current transformers are nonreplaceable in the field of protection and measurement for decades, but the electromagnetic current transformers can not meet the development of the electric power system for the reasons of magnetic saturation, ferro resonance, little dynamic range, narrow service band and so on。With the popularization of microcompute, It will be irreversible to apply microcompute in the protection and measurement, the equipments do not need the current transformer with high power, so the rogowski coil can apply on the field of protection and measurement. The advantages of simple structure, good linearity, no magnetic saturation, widely measure band make it fit sample in optical-electric current transformer nicely.While, there also have many new problems in applying Rogowski coils. From the theory of Rogowski we know, the output voltage is differential relationship to the input current, which need an integral block. In addition, to the protection equipment connect to the Rogowski coil directly, regular protection measurement device can't meet the request, it call for a special device. At the same time as a fast developing interface in these years, USB is a superior serial interface for its speed, popularization and practicality. The main work of the paper is for these cases. There are analog integral and digital integral. It was taken into account that the analog integral calls for high performance components, and hard to compensate, so the first part of my work is integral arithmetic analysis and simulate. Choose the proper sample and compare by two means.First is to compare actual value to the calculated, and second is analysis of the effect on harmonic wave. Take Fast Fourier Transform Algorithm to the samples fore-and-aft integral, and compare the amplitude and angle.The other part of work is a digital protection test device with USB interface. Simulate the fault states and get the data correspondingly on PC, then transfer the data to the tested protection equipment through USB and DA. The device has achieved the basic functions of testing, and it fully meets the specific of USB1.1. Which not only fulfill PnP, WMI, power, communication, but also control AD, DA and RAM. This is a profitable attempt to using USB on the electric power system.