Application of magnetic field detection for non-contact measurement of leakage current in low-voltage distribution network

Traditional methods for measuring leakage current typically require direct contact with the circuit, a practice that increases operational safety risks and makes it difficult to detect weak leakage currents, thus rendering leakage current measurement particularly challenging. Therefore, a non-contact leakage current measurement method based on magnetic field detection for low-voltage distribution network lines is proposed. A monitoring framework for leakage current in low-voltage distribution network lines is constructed. In this framework, the transducer module employs a non-contact magnetic modulation DC leakage current transformer to detect the magnetic field around the low-voltage distribution line, capturing the magnetic field variations caused by weak leakage currents to obtain the voltage waveform offset across a sampling resistor, thereby achieving accurate leakage current acquisition. Subsequently, an adaptive filter is utilized to suppress noise and interference signals in the leakage current signal. The filtered leakage current signal is transmitted to an STM32 microcontroller, which converts the signal into a leakage current value and determines the leakage location by injecting a specific frequency signal at the neutral point of the low-voltage distribution network line. Leakage information is displayed on an LED bar graph, and an alarm is triggered when the leakage exceeds the threshold. Simultaneously, leakage data are uploaded in real time to a host computer via a Bluetooth module, facilitating monitoring by the administrator. This method integrates magnetic modulation detection, adaptive filtering, and neutral-point frequency injection-based localization, overcoming the limitations of traditional contact measurement methods—such as high safety risks—as well as the difficulties in detecting weak leakage currents and accurately locating faults in non-contact techniques. It promotes the transformation of leakage current measurement technology from manual operation toward intelligent, safe, and precise solutions. By innovatively combining a magnetic modulation transformer with an adaptive filtering algorithm and incorporating a neutral-point frequency injection localization scheme, high-precision measurement and localization can be achieved without physical contact with the circuit, addressing the core challenges of leakage current measurement in complex low-voltage substation environments. Experimental results show that the leakage current measurement accuracy of this method reaches ±1 mA, with a minimum detectable leakage current of 1 mA. The signal clutter suppression rate reaches 92%, and the leakage fault location error is controlled within 0.2 m. When the threshold is exceeded, an alarm is triggered within 0.5 s. This approach significantly reduces manual testing costs and electric shock risks, minimizes equipment damage and safety accidents caused by leakage currents, and provides reliable technical support for the safe and stable operation of distribution network electrical systems.