Quasi-distributed fibre-optic sensor for high-voltage measurements

Abstract

The recirculation measurement method is used to control high voltage. The quasi-distributed fibre-optic sensor was constructed as a closed optoelectronic circuit formed by a tunable radiation source, sensitive elements separated by spectral reflective elements, avalanche photodiodes and a regeneration block. A dual-wavelength tunable fibre ring laser was used as a radiation source had an output radiation power of 4.5 mW, two generated wavelengths separated by 200 GHz with a line width of 22.8 GHz. The sensitive element of this device was the single mode optical fibre, wound onto the piezoceramic tube. The measurement principle is based on the inverse transverse piezoelectric effect, as a result of which the applied electric voltage causes a change in the dimensions of the piezoceramic tube and the length of the wound optical fibre. Based on the theory of coupled modes, the spectral-energy parameters of five adjacent fibre Bragg gratings in the spectrum were simulated and the characteristics of the gratings were established, allowing them to be used as spectral-selective elements. Changing the recirculation frequency at different wavelengths allowed the electric voltage to be monitored at different points with high accuracy. The resolution of these sensors is estimated to be 4.3 Hz/kV for a piezoelectric ceramic tube radius of 12 cm. Relative accuracy of 0.30–0.45 % for the PZT-5H at the multi-point measurements is achieved in the voltage range of 20 –150 kV. The system is designed for automated measurement of electrical voltage at distribution transformer stations and high-voltage power lines.