Fiber-optic voltage sensor for SF6 gas-insulated high-voltage switchgear

We present an optical-fiber voltage sensor for 170-kV gas-insulated high-voltage switchgear. The sensor is based on the converse piezoelectric effect of quartz. The full voltage is applied to a cylinder-shaped quartz crystal. The resulting alternating piezoelectric deformation of the crystal is sensed by an elliptical-core dual-mode fiber, which is wound onto the circumferential crystal surface. The fiber is interrogated by low-coherence interferometry. We address the dielectric design of the sensor and verify its dielectric reliability under ac overvoltages and lightning impulse voltages. We then investigate the sensor performance, including accuracy, dynamic range, bandwidth, and temperature dependence.