Design of Light Emitting Diode-Based Fiber Optic Current Sensor and Its Application in Pollution Flash Prevention in Digitalized Substations

Prevention of pollution flash in electrical equipment in digitalized substations and transmission lines has always been a crucial part of power operation. In order to prevent pollution flash, it is essential to detect the contamination of electrical equipment. The measurement of leakage current is a fundamental aspect of preventive pollution flash work in electrical equipment. Applying fiber optic current sensors to online monitoring systems in the power system offers advantages such as resistance to harsh environments, immunity to electromagnetic interference, and resistance to chemical corrosion. This study designs a unidirectional half-wave fiber optic current sensor based on Light Emitting Diodes (LED) for selectively observing the positive and negative half-cycles of leakage current. Due to the light emission and unidirectional conduction characteristics of LED, with a well-designed circuit, LED performs photoelectric conversion on the current, allowing the sensor to selectively measure the positive and negative half-cycles of leakage current. Subsequently, a combination circuit of silicon detectors and amplifiers is used to complete the photoelectric conversion, facilitating voltage signal measurement. In experiments, the response of the unidirectional half-wave LED fiber optic current sensor reached 37.8 mV/mA, with a detection bandwidth range between [1.2 kHz, 9.8 kHz]. In leakage current tests, using the leakage current of insulators as a reference, experiments were conducted using the voltage boosting method. As the applied voltage increased, the leakage current displayed on the sampling resistor increased, and the measurement waveform indicated that the sensor could correctly select the unidirectional half-wave. In leakage current and salt density tests, the designed fiber optic sensor accurately reflected the exponential relationship between insulator leakage current and contamination, demonstrating the practical value of the designed fiber optic current sensor.