Analysis of the Effects of Dust Accumulation on 33kV Line Insulators

Abstract

High voltage insulators always fail by having invisible and visible cracks and sometimes broken into pieces making the power system vulnerable to preventable losses. It is imperative to select the right type of insulator to withstand the nominal voltage based on design. Dust on the surface of insulator tends to reduce the reliability of the high voltage insulator by reducing the reliability and quality of power systems since it will generally lead to regular loss of power supply. To validate the insulator suitable for high voltage system, it is evident by experimental procedures to note the effect of various kinds of artificial contaminations on 33kV insulators (porcelain and polymeric insulator types). Dust types utilized in the experiment include cement dust, sea-salt, local dust and urea dust. Based on IEC 60507 standard, insulator specimens were polluted by artificial means. The specimens after pollution were left unattended to up to 24hours for natural drying. This experimental procedure continued for 7 days to get a significant and visible pollution on the surface of each insulator. This process was ideally used to check the break-down voltages and leakage currents as a way of probing into the effect of dust on the surface of the insulator. The results realized in this process are clear indications that salt and urea contaminations will affect porcelain and polymeric insulators more. In an attempt to compare, it was seen that cement pollution does not significantly affect porcelain and polymeric insulators. Maximum leakage currents associated with urea pollution and salt pollution tend to be higher because urea can reabsorb water molecule. The results also showed that polymeric insulators have higher break-down voltage than porcelain insulators. Comparatively, the effect of contamination is more on porcelain insulators than on polymeric insulators. Salt, cement and urea contaminations have higher effects on porcelain insulators than on polymeric insulators. The break-down voltage of polymeric insulators in salt contamination is 17% higher than in porcelain insulators, the break-down voltage of polymeric insulators in cement contamination is 22% higher than in porcelain insulators and the break-down voltage of polymeric insulators in urea contamination is 31% higher than in porcelain insulator. The method of pollutions and collection of the test results are in accordance with IEC 60507 standard.