| The errors of the current transformers directly affect the error of the electric energy measurement. Therefore, the necessity of monitoring the errors of the current transformers is unsuspicious. Currently, the separation of power generation and transmission from electric power industry which carries out the system reform makes the accuracy and fairness of the electric energy measurement highly concerned by all parties. In order to guarantee the accuracy of the electric energy measurement, we need to monitor the on-line operation current transformer without power cut.The paper proposes a method to calibrate the current transformers on line. First, we synchronously measure the current of the bus-bar and the current transformer on-line, then, by comparing the result to realize the monitor. The method based on a measurement technology of electronic current transformer. In the paper we introduce all parts including technical plan and error distribution firstly. Subsequently, we design the hardware and software correlated to the system, including, a clamp-shape air-coil based on PCB, also a circuit which controlled by the programming in the MSP430F1611 realizes synchronous sample and optical fiber communication in the high voltage side and a circuit which also controlled by the programming in the MSP430F1611 realizes data receiving in two Channels,PC communication and analogue output in the low voltage side.The experiment shows in the part of clamp-shape air-coil based on PCB in passing integral circuit, the changes of the ratio error less than 0.05%,the changes of the angle error less than 0.03°in 50Hz; In the part of synchronous sample used analog to digital convert and data communication, the changes of the error less than 0.03%,also, the changes of the error less than 0.02% when the frequency changes from 49.8Hz to 50.2Hz.The design realizes 0.1 lever accorded with the technical requirement of the system and finishes the target of the on-line calibrate to the current transformer. |
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