Mr. Ruokanen has an M.Sc. degree in Materials Science from the University of Technology in Helsinki, Finland. Before joining PPC in 2014, he held several leading technical positions at Maxwell Technologies in both the Ultra-Capacitor and HV Capacitor Divisions. He is a member of Cigré Switzerland.
Studies have defined four key ageing mechanisms that can affect the service life of C-120 and C-130 high strength alumina porcelain insulators: a) expansion of cement, b) corrosion of metal parts, c) mechanical and electrical stresses on core, and d) drying out bitumen. Resistance against mechanical and electrical stresses in ceramic insulators relates mainly to microstructure. This presentation reviews findings from a recent study of porcelain microstructure containing intentionally placed quartz particles as calibrated defects. The objective was to evaluate impact on resistance against mechanical stresses and quantify the number and particle size of critical residual content.