The Study of High-precision Power Frequency Leakage Current Sensor

The on-line monitoring leakage current of high voltage equipment is an important technique to ensure safe generation and transmission of electricity. This paper focuses on the detection of the leakage current of the zinc oxide surge arrester, and the leakage current is very small (
$\mu \mathrm{A}$
), especially the phase error must be very mall. So a high-precision leakage current sensor is needed. Due to the serious field interference and strict measurement accuracy requirements, a Rogowski coil with magnetic core was designed, which was compensated by shunt capacitance. By comparing material performance of cold-rolled silicon, ferrite and nanocrystalline alloy and analyzing the influence of all parameters to the performance of the sensor, nanocrystalline alloy is found to be the most suitable material for the sensor. In addition, ambient temperature plays an important role in the sensor accuracy, which could be solved by choosing the right capacitor and core material. Temperature not only directly affects the magnetic permeability and capacitance value, but also causes the thermal expansion of the winding and the magnetic core. Considering the influence of temperature comprehensively, the temperature influence coefficient of the sensor transfer function is calculated to be 1.216 ppm/°C. By error contrast experiments to the sensor at different temperatures, the temperature coefficient of the ratio difference and the angle difference were obtained respectively.