Multiphase digital synchronously sampling photoelectric current mutual inductor and its measuring method

Abstract

The synchronously sampling multiphase digital photoelectric current mutual inductor consists of several high voltage side circuits, several transmitting fibers and one low voltage side circuit. The basic characteristics of the digital photoelectric current mutual inductor include the control of several phase circuit sampling in the high voltage side by the clock from the low voltage side, the hardware implementation of the simultaneous sampling of the three phase, A, B and C, current, the simultaneous sampling based on the united clock GPS and software quasi-synchronous sampling tracking power network frequency, and the simple combination of photoelectric current / voltage measurement. The present invention can raise the measurement precision of current in power system and optimize the interface performance of secondary output to accommodate the development of digital, microcomputerized and intelligent electric power measurement and protection.

Description

(1) Technical field [0001] The invention belongs to the field of power system measurement, in particular to a digital electronic current measuring device combined with photoelectricity. (2) Technical background [0002] Conventional CTs have been used to measure current in power systems for over a hundred years. It provides input signals for the metering, relay protection, control and monitoring of the power system, which is of great significance. With the increasing power capacity and higher voltage level transmitted by the power system, conventional CT has insurmountable problems due to its sensing mechanism: (1) The insulation technology requirements are complex, bulky and heavy, and the cost is high; (2) The saturation of the transformer iron core under the fault state limits the transient response speed and accuracy of the CT; (3) Due to the influence of the magnetic saturation of the iron core and the hysteresis loop, the transient output current of the CT is seriousl...

AI Technical Summary

Problems solved by technology

With the increasing power capacity and higher voltage level transmitted by the power system, conventional CT has insurmountable problems due to its sensing mechanism: (1) The insulation technology requirements are complex, bulky and heavy, and the cost is high; (2) The saturation of the transformer iron core under the fault state limits the transient response speed and accuracy of the CT; (3) Due to the influence of the magnetic saturation of the iron core and the hysteresis loop, the transient output current of the CT is seriously distorted. This distortion increases the complexity of the relay protection device

Therefore, it is very difficult to accurately judge the degree of CT saturation in real time

The distortion of the secondary current waveform will directly affect the rapid and accurate judgment of faults, thus affecting the rapidity, sensitivity, selectivity and reliability of relay protection, especially the differential protection, and even malfunction

Because the three phases are individually controlled, the three-phase sampling is not synchronized, and the waveform of the three-phase current on the high-voltage side cannot be reproduced on the low-potential side

When measuring the three-phase power of the power system, three-phase synchronous sampling is required, otherwise, the three-phase power sampling time is different, the error of the measured power is large, and even wrong results may appear

In addition, if the three-phase current sampling of the power system fault recording and high-voltage line fault location system is not synchronized, erroneous results will occur

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