Photoelectric Transformer Calibrator Based Research IEC61850

With the application of digital substation, electric transformer has got a rapid development. The principle of electric transformer is different from the conventional electromagnetic transformer. Its secondary output has two ways:analog output and digital output. For digital output electric transformer, its output is digital sequence, with the absolute measurement detection to do the error monitoring, having a high requirementon the accuracy of acquisition card and stability of the power supply. Error measurement method is completely different from the traditional transformer. And its requirement on the test is more complex, so we must develop a new calibration system.This thesis proposed a calibration method for digital output of electric transformer, and designed a electric transformer calibration instrument based on IEC61850. Synchronization comparative method was used to do the sampling in the testing and standard transformers. The error was calculated according to the error definition.For standard transformer, signal measurement is directly detected using the dynamic signal acquisition card whose accuracy is one ten thousandunder the coordination of the trigger signal. Measurement capture card is configured as an analog trigger mode, falling along trigger, sample10points before triggered, the trigger voltage is3.2V, atthe rate of100kHz, sampling24,000points, using the fast Fourier transform to solve initial phase, effective value and frequency informationof the continuous10waves. The delay time was calculated according to the linear slope of the trigger signal, for compensation calculations of the angle difference.Consolidated unit of the tested electric transformer was synchronously interpolated under the coordination of the synchronization signal, sending data packets continuous of the10cycle of waves, the number of packets was captured based on the sampling rate configuration of the combined unit. Using C language to parsedata packets in accordance with IEC61850-9-1, IEC61850-9-2, extract digital sequence from electric transformer output. For IEC61850-9-1data packets containing multiple ASDU, extracting multiple the digital sequence before extracting data packet sampling counter value to determine whether data sequenceis valid or not, using the fast Fourier transform to the frequency domain analysis of the signal sequence, solving initial phase, effective value of the synchronization time.After commuting photoelectric transformer current from quadratic to linear according to the error definition,the difference between the actual linear and the converted linear current was showed in a percentage of the linear current, the actual linear current is calculated by the quadratic current multiple rated transformation ratio. The value of initial phase of electric transformer minus the value of initial phase ofthe standard transformer, then minusrated delay time of the merged unit and network delay, then get angle difference of electric transformer, expressed in angle.For the standard transformer acquisition card, accuracy calibration was compared using eight and half digital table. The measurement precision is less than one ten thousandth for standard transformer whose communication signal is more than5%. For small signal measurement accuracy is less thanfive ten thousandth, can finish the calibration of0.02and below0.02electric transformer. In Yongjing Gansu Province,330kV digital substation was do the site EMC testing using this program, its long-term stability calibration can make electric transformers in the whole station worked well.