Insulating Characteristics of Dimethyl Silicone in Bare and Insulated Uniform Field Gaps

Impulse and sixty-hertz breakdown tests were conducted on stationary and circulating 50 centistoke dimethyl silicone using bare and insulated uinform field elect-rodes. The electrode insulation materials used were polyamide paper, and Kraft paper thermally upgraded with dicyandiamide. The test results show that insulating the electrodes, significantly increases the sixty-hertz and impulse dielectric strengths of silicone. Under most conditions, the uniform field insulating characteristics of dimethyl silicone are comparable to those of conventional transformer oils; however, the bare electrode sixty-hertz strength of silicone is approximately 20% lower than that of transformer oil.