Abstract: A sensor assembly for monitoring an internal condition of a transformer. The assembly includes: a body for location outside a tank of the transformer, the body housing an electronics assembly including body sensors coupled to a processor; a probe extending from the body for insertion into a tank of the transformer; a number of probe sensors coupled to the processor disposed at or toward a remote end of the probe for sensing conditions within the tank. The processor is configured to process signals from the probe sensors and the body sensors to produce signals for assessing one or more of: transformer core temperature; transformer insulation state; partial discharge; mechanical state of transformer; chemical state of transformer.

Abstract: A method of determining polymerisation of transformer insulation within a transformer. The method includes the steps of measuring a first and second moisture activity of oil in a transformer, and a first and second temperature of the transformer. The method further includes calculating the ratio of the gradients of the moisture equilibrium curves associated with the moisture activity and the temperature. The calculated ratio can then be used to characterise the polymerisation of the insulation and age of the transformer.

Abstract: A method of determining polymerisation of transformer insulation within a transformer. The method includes the steps of measuring a first and second moisture activity of oil in a transformer, and a first and second temperature of the transformer. The method further includes calculating the ratio of the gradients of the moisture equilibrium curves associated with the moisture activity and the temperature. The calculated ratio can then be used to characterise the polymerisation of the insulation and age of the transformer.