Optical isolation system for HV measurements - has light guide with outer resistive sheathing between probe and receiver and light modem system

摘要

The isolator consists of a fibre-optic light guide (2) enclosed in a plastics sleeve. The sleeve has an outer coating of resistive material (4). The light-guide is placed between a current-measuring device (7) coupled to the high-voltage line (5) and a receiver (6). A modulated light transmitter (9) is coupled to the high-voltage end of the light-guide. At the low-voltage end of the light-guide, the light is demodulated and a signal proportional to the measured current is available at the output terminals (10, 11). The upper end of the resistive coating is at high potential and a voltage tap (17) provides power for the measuring and transmitter circuits via a supply unit (18). The lower, low-potential end of the coating is connected to the receiver housing and earth.