IEC 61125:2018 pdf download

IEC 61125:2018 pdf download.Insulating liquids – Test methods for oxidation stability Test method for evaluating the oxidation stability of insulating liquids in the delivered state
1 Scope
This document describes a test method for evaluating the oxidation stability of insulating liquids in the delivered state under accelerated conditions regardless of whether or not antioxidant additives are present. The duration of the test can be different depending on the insulating liquid type and is defined in the corresponding standards (e.g. in IEC 60296, IEC 61 099, IEC 62770). The method can be used for measuring the induction period, the test being continued until the volatile acidity significantly exceeds 0,1 0 mg KOH/g in the case of mineral oils. This value can be significantly higher in the case of ester liquids. The insulating liquid sample is maintained at 1 20 °C in the presence of a solid copper catalyst whilst bubbling air at a constant flow. The degree of oxidation stability is estimated by measurement of volatile acidity, soluble acidity, sludge, dielectric dissipation factor, or from the time to develop a given amount of volatile acidity (induction period with air). In informative Annex B, a test method for evaluating the oxidation stability of inhibited mineral insulating oils in the delivered state by measurement of the induction period with oxygen is described. The method is only intended for quality control purposes. The results do not necessarily provide information on the performance in service. The oil sample is maintained at 1 20 °C in the presence of a solid copper catalyst whilst bubbling through a constant flow of oxygen. The degree of oxidation stability is estimated by the time taken by the oil to develop a determined amount of volatile acidity (induction period with oxygen). Additional criteria such as soluble and volatile acidities, sludge and dielectric dissipation factor can also be determined after a specified duration. In informative Annex C, a test method intended to simulate the thermo-oxidative behaviour of ester insulating liquids (headspace of air at 1 50 °C for 1 64 h) is described.
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: · · IEC Electropedia: available at http://www.electropedia.org/ ISO Online browsing platform: available at http://www.iso.org/obp 3.1 unused insulating liquid insulating liquid that has not been used in, or been in contact with electrical equipment or other equipment not required for manufacture, storage or transport Note 1 to entry: See also IEC 60296, IEC 61 099 and IEC 62770. 3.2 recycled insulating liquid insulating liquid previously used in electrical equipment that has been subjected to re-refining or reclaiming (regeneration) off-site Note 1 to entry: Any blend of unused and recycled oils is to be considered as recycled. 3.3 oxidation stability ability of an insulating liquid to withstand oxidation under thermal stress and in the presence of oxygen and a copper catalyst Note 1 to entry: Oxidation stability gives general information about the stability of the insulating liquid under service conditions in electrical equipment. The property is defined as resistance to formation of acidic compounds, sludge and compounds influencing the dielectric dissipation factor (DDF) under given conditions. Test durations for insulating liquids are described in the corresponding standards. 3.4 induction period with air graphical representation of the oxidation rate over the entire period which can be obtained by titrating volatile acidity daily (or at other suitable time interval) and plotting the cumulated results against time Note 1 to entry: The induction period with air is determined by reading the time corresponding to 0,1 0 mg KOH/g volatile acidity in the case of mineral oil. In the case of ester liquids a higher value needs to be established.