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Aerospace electrical systems are continuing to increase their voltage levels to meet the on-board power demands of more-electric aircraft (MEA) where hydraulic and pneumatic systems are replaced with electrical equivalents. This trend will only continue as hybrid and all- electric aircraft are developed. These higher power demands require the use of higher voltages and as such it is essential to explore the behaviour of the insulation system in the aerospace environment. This insulation must operate in an environment where the operating temperatures range from 250°C to -65°C, the air pressure is around one tenth of that at ground level and where the levels of humidity and ozone vary rapidly. Understanding the impact of these variables on aircraft high voltage insulation systems is crucial in predicting their behaviour and lifetime.

As aircraft move to using higher voltages, there is an increased risk of electrical failure if clearance and creepage distances of electrical apparatus, especially printed circuit boards (PCBs) are not appropriately maintained. However, conservatism can lead to dimensions being artificially enlarged leading to significant penalties in terms of weight / volume. One failure mode that can exist on insulation of PCBs is electrical tracking across surfaces, particularly those that are contaminated (this mode of failure being distinct to arc tracking in cables). This can eventually lead to electrical failure in the form of a short circuit and could pose a fire risk in some systems. For precise dimensioning of insulation within equipment, it is necessary to understand the mechanisms of electrical tracking as influenced by different environmental conditions.