Insulation is one of the key components of any high voltage transmission line to ensure continuity of service and safety in the event of faults. It must therefore be properly designed for climatic and environmental service conditions, including amount of rainfall, frequency of atmospheric discharges, pollution level, etc.
Insulators can be classified according to their housing material into ceramic types, which include glass and porcelain insulators, and polymeric types – also called composite insulators. Ageing of insulators on transmission lines can greatly affect reliability and it has been found that as much as 50% or more of maintenance costs for power networks are due to insulator failure.
Rate of ageing and deterioration of insulators can be even worse when they operate in problematic areas with high ageing factors such as pollution, moisture, light, ultraviolet radiation, dust, heat and atmospheric pressure. For example, Fig. 1 shows a schematic of ageing factors applicable to polymeric insulators, where the main environmental stresses are heat, acidity, UV radiation, salinity and rain.
Fortunately, well-designed and properly specified polymeric insulators can offer stable performance even under the worst environmental conditions and sustain their properties over a wide temperature range. This makes them suitable for application in areas with challenging climatic and geographic conditions.
In the case of the power system in Peru, there are three well defined regions that have much different climates and environments. The coastal area is characterized by salt pollution, high humidity and scarce rainfall. Here, the main challenge has been to reduce maintenance costs related to frequent cleaning and washing of insulators. By contrast, transmission lines in the Andes are located up to 4500 m above sea level, with high rainfall and soil resistivity greater than 5000 ohms-meter. The main problem for insulators installed in this service area is related to atmospheric discharges and high levels of solar radiation. Finally, in the Amazon Forest, dense vegetation, heavy rain and high isokeraunic levels are all relevant to maintenance requirements. The main problems there are related to atmospheric discharges and growth of fungi and lichen on insulators.
Attend the 2023 INMR WORLD CONGRESS in Bangkok, Thailand to learn from a technical lecture by Samuel Arturo Asto Soto, Transmission Line Coordinator for the Peruvian Power Grid. Based on experience with polymeric insulators installed in all distinct regions in Peru, he will describe the main aspects related to their failure as well as explain the best replacement strategy and how their proper maintenance has been decided.
