The performance of composite insulators in Tropical coastal areas of Tanzania

In order to investigate the performance of composite insulators in tropical coastal areas in Tanzania, different types of 33kV composite insulators were installed at three different sites exposed to different pollutions. Apart from selected sites for installation, the insulators that have been in-service several years ago were periodically investigated and tested too. By using Swedish Transmission Research Institute (STRI) method, silicone rubber (SIR) and RTV coated porcelain insulators preserved the hydrophobicity properties and with respect to leakage currents and flashover voltages performed in laboratory performed well than ethylene propylene diene monomer (EPDM). Silicone rubbers in particular were found with biological growths (algae) at some sites and had influenced the performance of insulators. Dry bands and black soot were also found on two biologically contaminated silicone rubber insulators. The EPDM insulator materials showed surface degradation under contaminated condition. Deterioration of EPDM insulator materials initial performance seems to be a rather rapid occurrence and hence may result in leakage current and flashover. This information is useful for assessing the condition of similar non-ceramic insulators in use.