In view of the characteristics of the small amplitude of a current signal, an all-optical fibre small-current sensor for partial discharge is devised. A novel type of sensor head with electric winding light is proposed. A complete optical model of the optical fibre current sensor is developed under the effect of polarization error factors. In addition, the effect of polarization error factors on the optical fibre sensing system is simulated. The simulation results show that as the extinction ratio increases, the output relative error of the optical fibre small-current sensor decreases. The effect of the fast and slow axis misalignment errors of a polarizing beam splitter is similar to the effect of the alignment angle error of an optical fibre polarizer. It is observed that the relative error curve follows a sine function. Meanwhile, the output relative error increases first and then oscillates with an increase in the linear birefringence. We conclude that the linear birefringence of the sensing optical fibre is the main error source for the measurement accuracy of the sensing system. Finally, an experimental system for the optical fibre small-current sensor is implemented. The experimental results show that the effect of linear birefringence on the fibre current sensing system can be suppressed by introducing a large amount of circular birefringence into the sensing optical fibre. The theoretical mechanism of these errors is analysed, which can be applied to implement corresponding measures to reduce the effect of error factors on the sensing system and further improve the measurement accuracy of the optical fibre small-current sensor.

中文翻译：

---

局部放电全光纤小电流传感器偏振误差分析

针对电流信号幅值小的特点，设计了一种用于局部放电的全光纤小电流传感器。提出了一种新型的带电绕组灯的传感头。在偏振误差因素的影响下，建立了光纤电流传感器的完整光学模型。此外，还模拟了偏振误差因素对光纤传感系统的影响。仿真结果表明，随着消光比的增大，光纤小电流传感器的输出相对误差减小。偏振分束器的快慢轴未对准误差的影响类似于光纤偏振器的对准角误差的影响。观察到相对误差曲线遵循正弦函数。同时，输出相对误差首先增加，然后随着线性双折射的增加而振荡。我们得出结论，传感光纤的线性双折射是传感系统测量精度的主要误差源。最后，实现了光纤小电流传感器的实验系统。实验结果表明，通过在传感光纤中引入大量圆形双折射，可以抑制线性双折射对光纤电流传感系统的影响。分析了这些误差产生的理论机理，可用于实施相应的措施，减少误差因素对传感系统的影响，进一步提高光纤小电流传感器的测量精度。