Analysis of Cement Deterioration in Outdoor High-Voltage Insulator

Abstract

Suspension type porcelain insulators used in overhead transmission lines comprise metal, ceramic, and cement. The deterioration of cement can lead to mechanical separation. For the degradation analysis, varied sizes of pores ranging from a few µm (capillary pores) to tens to hundreds of mm (detectable by naked eyes) were considered. Cracks that were hard to view with naked eyes were identified by staining with a fuchsine solution. The hydrogen ion concentration and pH value indicate the extent to which the cement is deteriorated. The longer the cement is used, the lower its pH value. High mechanical strength is considered an important advantage of porcelain insulators, and it may decline, if the cement is used for a longer period of time. Water ingress may also occur, resulting in expansion, due to the rehydration of the cement. The process and mechanism of expansion of cement, due to infiltration of water were described. As a method of analysis, a universal indicator was employed to evaluate the pH changes in cement. It was observed that the pH value was 12-13 for new products. However, for products that were used for 52 years, the pH value was under 7, which indicated an acidic tendency, due to deterioration.

Analysis of the Deterioration of High-Voltage Insulators in Service Areas Due to Contamination Factors

“…The process of deterioration accelerates with a high concentration of hydrogen ions, high humidity conditions, and the presence of silica, a reactant. 9,15,18,[23][24][25] Akali silica reactions majorly contribute to the degradation of cement due to the high concentration of alkali-reactive aggregate compounds and humid environments.…”

“…The closer the installation site is to the shore, the higher are the pollutant conductivity and chances of current leakage. 13,14 The deterioration of the cement was classified according to its service time. Waterjet cutting was performed to analyze the cement considering that the use of water-based cutting is highly recommended to avoid heat damage that often occurs when a diamond saw is used for cutting.…”