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Date of Publication:2022-10-10

Journal:电工技术学报

Issue:4

Page Number:66-72

ISSN No.:1000-6753

Abstract:A laser powered electronic current transformer (ECT) for protection or metering purposes based on low power current transformer (LPCT) used in high voltage power system has been developed to overcome the disadvantages of the measuring accuracy of air core coils that can be influenced by temperature and manufacturing technology. The principle of LPCT and the structure of ECT are presented in the paper first. The primary converter includes two primary sensor data channels with active temperature compensation and self-calibration at the high voltage side. This allows even higher accuracy over an extended temperature range and a wide current range. The secondary converter with analog and digital output converts the signal from primary converter and send signal to control the primary converter. Data signals include synchronization and calibration can be transmitted via the same optical fiber that is used to transmit power to primary converter. Some online supervisory functions are also successfully accomplished in this system, and this form of preventive maintenance or built-in test will increase system reliability by giving advance warning and indicating necessary maintenance. The experimental results show that the primary converter together with the improved circuit driving fiber transmitter can work reliably consuming averagely no more than 40mW power. Data signal can be transmitted at baud rate as fast as 200kb/s from the second to the primary converter, and 2Mb/s at the opposite direction. The ECT can meet the accuracy requirement of IEC 6044-8 standard 0.2S class for measuring current transformer and 5TPE class for protective current transformer.

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