Investigation of water treeing development in silicone rubber under sharp and blunt needles

Silicone rubber (SiR) is a common polymeric material that has been used as solid insulation in cable especially for end termination and two cables connection insulation. However, cable insulator is easily exposed to moisture if the cable is defected after installation. This causing water tree to be produced whenever high voltage is applied. Water tree development worsens when there is micro protrusions exist at the conductor's surface. An experiment is developed in order to observe the relation between water tree and micro protrusion and their effect toward insulation material. This experimental development has prepared two types of sample testing which are sharp and blunt needles. These sharp and blunt needless are referred to the micro protrusion appear on the conductor's surface. Furthermore, the needle is exposed to salt solution that acts as a moisture contaminant. The samples have been applied high voltage stress at 10kV. As a result, water tree development with different shape and length has been observed on both samples. The tip shape of the needle influenced the development of the water tree. The sample of sharp needle tip precede in water tree formation because it produces stronger and larger area of electrical field.