A New Current Transducer for On-Line Monitoring of Leakage Current on HV Insulator Strings

Leakage current measurement and its harmonics have been widely used for the pollution level estimation of HV insulator strings. However, the solutions available to applications into transmission lines and substations are few and it reduces the creepage distance (mm/kV), must be installed by de-energizing the electrical power system or do not allow the characteristic harmonics of the leakage current to be obtained. This paper presents the design, implementation, testing, and experimental validation of a transducer for measuring and online monitoring of leakage currents on high-voltage insulator strings. The transducer is composed of a clamp-type current transformer with a supermalloy material core. The leakage current is reconstructed from the transducer output voltage by applying the Fast Fourier Transform (FFT) and its own inverse transfer function, which allows it to obtain the leakage current with its characteristic harmonics and reduces the electromagnetic noise present in power systems. The output voltage of the transducer was acquired, processed, and transmitted using a dedicated device installed in the HV tower. The proposed transducer was first tested on an insulator inside an artificial fog chamber according to the IEC 60507 standard. The transducer was experimentally validated on an insulator string in a 220 kV substation. The results showed that the designed transducer measured the leakage current and its harmonics with an average error less than 1.76%. With these results the transducer can be used for the on-line monitoring of pollution levels of insulator strings without reduces the creepage distance.