An Exterior Optical Fibre Sensing Technology Used for Interface Pressure Measurement Between Cable and Accessory

Interface pressure between cable and accessory is the key to ensure the long-term reliable operation of cable accessories. The traditional measurement method of interface pressure is off-line measurement through a built-in piezoelectric sensor. However, this method is difficult to operate and damages the interface structure. In addition, the offline measurement cannot reflect the real-time dynamic change of interface pressure during the operation of cable accessories. Therefore, this paper proposes a new method for the on-line measurement of interface pressure between cable and accessory by means of an exterior optical fibre curvature sensor, whose design mechanism is based on the pure bending theory of optical fibre. Then the relationship model involving the exterior curvature of the cable accessory, the radial displacement and the inner interface pressure is established. Finally, interface pressures of the 8.7/10 kV cable accessory under different expansion ratios are measured by the calibrated optical fibre curvature sensor. The measurement results show that the optical fibre curvature sensor measures the exterior curvature of the accessory accurately; the average sensitivity reaches 7.679 nm/mm ⁻¹ , and the measurable curvature ranges from 0.03 to 0.05 mm ⁻¹ . The conversion results of interface pressure are basically consistent with the results measured directly by a traditional piezoelectric sensor or simulated mechanically by finite element software. Therefore, the exterior optical fibre sensing technology proposed in this paper is expected to be used for the on-line measurement of the interface pressure between cable and accessory.