Rogowski Coil Transducer Based Condition Monitoring of High Voltage Insulators

In this paper, a proposed condition monitoring technique of high voltage insulators using Rogowski coil is presented. The proposed technique depends on the voltage signal that generated in Rogowski coil winding due to capacitive coupling between the insulator and the coil. A superimposed voltage signal is generated in the coil winding due to electromagnetic induction that occurs due to leakage current over the insulator surface during fog conditions. The output voltage signal from coil winding (i.e. due to capacitive coupling and electromagnetic induction) is directly analyzed using Fast Fourier Transform (FFT). The direct analysis of the output voltage signal from Rogowski coil without the need for current reconstruction reduces the complexity of signal processing. According to the obtained frequency spectrum of the output voltage signal, pollution level on insulator surface can be determined. In order to validate the proposed technique, an experimental setup is used. In experiments, high voltage pin type insulator is used and connected to a high voltage AC source. The insulator surface is sprayed with saline solution according to IEC 60815 standard to simulate different pollution levels. Also, the insulator surface is polluted with charcoal powder to simulate the non-soluble pollutants. For more validation, the experiments are extended to a cap and pin – type high voltage insulator. The obtained results show that the percent of 3rd/5th harmonics of the measured voltage signal increases with the increase in pollution level. Finally, the efficacy of the proposed technique is validated through the obtained results.