Development of a Dual-temperature Test Cell for Laboratory Ageing Experiment of Transformer Insulation Systems

As accelerated ageing tests in full-size transformers are impractical, laboratory ageing experiments are often used to understand the ageing process of transformer insulation systems. Three main types of ageing experiment set-up can be identified in literature: a functional life test model, a dual-temperature test cell and a single temperature test cell. A functional life test model is a scaled-down representation of transformer operation, but it is very expensive to run. A single temperature test cell is the simplest and most widely used laboratory test set-up but it cannot reflect the different temperature profiles and gradients found inside a real transformer. The dual-temperature test cell is less complicated and less costly than the transformer model and still has the ability to simulate the different temperatures experienced by transformer insulation. In a dual temperature cell the solid and liquid insulation temperatures are independently controlled, thereby overcoming the main disadvantage of the single temperature test cell method. In this paper, the design and construction of a dual-temperature test system based on the IEC TS 62332-1 technical specification is described and test results are provided to show that the test system fulfils the desired functions with stable conductor and liquid temperatures.