Comportarea cuprului de uz electrotehnic ?n uleiuri de transformator expuse cicl?rilor termiceBehaviour of electrical purposes copper in thermal cycled transformer oilsFull text in Romanian

摘要

The behaviour of household electrical copper foil immersed in various sorts of transformer oil has been studied by XRF, gravimetry, SEM and SEM coupled with ESD (EDAX). Measurements were made in three types of mineral oil and in three types of ester based oil (one synthetic ester-based oil and two vegetable-based ester oils). The experimental measurements on the sulphur content of oil, the copper foil changes in mass, the content of sulphur and oxygen, and the image of the copper foil surface was determined both before and after the exposure of the oil with copper samples to 1000 thermal cycles between –40 °C and 85 °C (temperature gradient of approx. 4 °C). The results indicated that the investigated ester based oils does not contain sulphur and does not corrode the copper foil – on which a continuous layer of Cu2O is formed during the exposure (as showed up by EDAX technique). In the case of mineral oils, the foil covers with a discontinuous film of Cu2O and presents pitting corrosion. The copper dissolution rate is determined by the sulphur content of the oil sample, varying in the range of 1.11?10–7 and 11.2?10–7 g/h?cm2.