Rong Jong Chang

Optimization of tracking resistance, erosion resistance and hydrophobicity for outdoor insulation materials

In additional to excellent weathering resistance, an outstanding outdoor high voltage insulation material must possess good tracking and erosion resistance, good hydrophobicity and fast recovery of hydrophobicity after arcing activity. Moreover, the material should retain good processability. It is shown that the optimum balance of all these properties can be achieved by a specially formulated silicone compound with no alumina trihydrate (ATH) and a polyolefin copolymer with medium level of ATH and a surface modifier.

Electrical activities associated with inclined-plane tracking and erosion test

A leakage current monitoring system was installed to measure the electrical activities including peak leakage current, average leakage current, cumulative charge, and number of leakage current pulses in four ranges: 1-5 mA, 5-15 mA, 15-50 mA and 50-200 mA during the inclined-plane test (ASTM D2303). The electrical activities were measured for two materials-a silicone without aluminum trihydrate (ATH) and an ethylene vinyl acetate copolymer (EVA) using the step voltage procedure. The results illustrated the intensity of the electrical activities associated with the applied voltages and the flow rates of the contaminant solution for the two polymers. The severity of the test was quantitatively defined by the detailed measurements of electrical activities. It was also demonstrated that even with intensive arcing, excellent tracking and erosion resistance can be achieved with both polymers. The additives and fillers are more important than the generic polymer types in achieving tracking and erosion resistance for polymer compounds.

Design of insulators for severe contamination

Under severe contamination, typified either by sand dust storm or heavy salt fog ceramic insulators experience problems such as high leakage current, burning of crossarms and flashover. Several years of field tests in heavily polluted areas around the world have demonstrated that hybrid insulators with highly protected creepage designs are very effective. In this paper mainly the Taiwans problem and its solution are addressed. Special insulator designs, along with excellent material properties, are required to reduce leakage current and prevent flashover. The manufacturing of such protected creepage designs requires polymeric materials with good processibility in addition to good tracking and erosion resistance and hydrophobicity.