Behaviour of Impregnated Composite Insulation Under High Voltage at Very Low Frequency

Low frequency tests using a ramped voltage waveform were conducted on sandwich type composite impregnated insulation consisting of paper and/ or polypropylene. Mineral and silicone oil were used as impregnants. Volt-current plots were used to analyze insulation behaviour. It is shown that the plots are useful in assessing the quality of the insulation. Losses are shown to occur due to inelastic deformation of the insulation.