正弦波调制FOCT调制回路故障对探测器输出特性影响

Influence of sine wave modulation FOCT modulation loop fault on detector output characteristics

为探究全光纤电流互感器(fiber optical current transformer,FOCT)调制回路故障对探测器输出信号影响,便于故障预测与故障诊断,文中首先建立包含光电回路相位延迟的正弦波调制FOCT输出信号数学模型,给出调制深度与驱动电压、二次谐波、四次谐波的数学关系式,分析定目标值调制器闭环调制、解调的基本方法。在此基础上通过建立数学模型分析调制深度对探测器输出光强峰值、平均光强、二次谐波、四次谐波的影响。据此提出发生调制回路故障时调制深度降低是导致探测器输出信号异常的关键因素,探测器输出平均光强增大、四次谐波降低、二次/四次谐波比值增加应作为调制回路故障的典型特征。最后开展实际FOCT模拟试验证明理论研究的有效性。

In order to explore the influence of the modulation circuit fault of the fiber optical current transformer(FOCT)on the output signal of the detector,and facilitate fault prediction and fault diagnosis,the mathematical model of sine wave modulation FOCT output signal which includes the phase delay between the optical circuit and the electrical circuit is firstly established in this paper.The mathematical expressions of modulation depth,driving voltage,second and fourth harmonic are given,and the basic methods of closed-loop modulation and demodulation of the target value modulator are analyzed.On this basis,a mathematical model is established to analyze the influence of modulation depth on the peak of the detector output light intensity,average light intensity,second and fourth harmonic.Therefore,it is proposed that the modulation depth decrease is the key factor leading to the abnormal output signal of the detector when the modulation loop fault occurs,and the increase of the average light intensity of the detector output,the decrease of the fourth harmonic and the increase of the second/fourth harmonic ratio should be the typical characteristics of the modulation loop fault.Finally,the practical FOCT simulation test is carried out to prove the validity of the theory.