A campaign for the ageing evaluation of station hollow core composite insulators after a number of years of service

The reliability of electric transmission network is strictly related on the quality and material reliability of its electrical equipment. Insulators play a role of paramount importance for the reliability of the grid. Silicon rubber hollow core insulators are being widely used replacing porcelain thanks to the advantages as pollution insulation withstand, safety and reduced life cycle cost. The environmental conditions combined with the electric field, may result in the insulator ageing depending on the design, technology and silicone compound formulation/quality. A standard monitoring or field-testing method for early detection would be helpful for life prediction and in the worst case to replace the equipment before failure. This paper is a common approach of a manufacturer of High Temperature Vulcanized (HTV) silicone rubber (and Liquid Silicone Rubber (LSR) as well) Hollow Core Insulators (HCI) and a Transmission System Operator (TSO) to combine an experience of 30 years with HTV silicone rubber HCI. The Italian TSO TERNA has been an early precursor of the use of composite insulators in the HV Equipment specifying silicone composite insulators for the housing of high voltage Current Transformers (CT) for the 170, 245 and 420 kV classes replacing porcelain for safety reason and aiming to a better behaviour in high contaminated area without incur in insulator washing anymore. This paper resumes the experience on technical evaluation of HTV silicone rubber HCI with same technology and base silicone polymer but different shed profiles over periods up to 30 years to evaluate ageing behaviour in harsh environments. Reinhausen Power Composite and TERNA based on such very long joint experience decided to start a campaign for the ageing evaluation selecting a number of sites falling between heavy and very heavy site pollution severity where Reinhausen Power Composite HTV HCI are installed in the Italian high voltage grid and defining a number of non-destructive tests in order to get as much as possible information on the ageing. Such campaign refers to HTV HCI with homogeneous insulator characteristics installed on CTs over a period of more than 15 years of operation on the 420 kV grid.