Study on the paper ageing in transformer oil using furfural concentration

Abstract

变压器油中糠醛浓度 ρ(C5H4 O2 )是绝缘纸老化程度的重要指标。实验证实了绝缘纸的拉伸强度与聚合度(DP)呈线性关系 ,ρ(C5H4 O2 )对数值与DP呈负线性关系 ,可使用高性能的液相色谱分析仪测 ρ(C5H4 O2 ) ,以判断绝缘纸的老化程度。水会加快绝缘纸中纤维链的断裂速度 ,而水又是绝缘纸老化过程中的生成物之一 ,故形成了绝缘纸老化的自催化 (正反馈 )过程 ,变压器各部分的温差使老化过程更加复杂。短期内 (几个月 ) ρ(C5H4 O2 )的显著变化表明变压器内部存在隐患并引发故障的概率相当大 ,故定期检测变压器中 ρ(C5H4 O2 )十分必要。 The concentration of the chemical furfural in transformer oil is well known to be an indicator of the extent to which the paper insulation of the windings has deteriorated. However, technical papers on the relationship between the loss of mechanical strength of the paper insulation in transformer and the increase in the concentration of furfural in the oil are to be found scattered over a variety of journals. The intention of this communication is to bring together the main findings of the laboratory investigations, and the rather fewer reports of field experience, for the convenience of power engineers. The linear relationship between the tensile strength and the degree of polymerisation (DP) of paper insulation has been demonstrated by several workers under laboratory conditions; and so has the negative linear relationship between the logarithm of the furfural concentration and the DP. The concentration of furfural in transformer oil is seen as a paper specific indicator of degradation and a method for measuring it using high performance liquid chromatography has now been standardized (IEC 1198). The presence of water increases the degradation rate of the cellulose chains and so, because water is also a product of the degradation process. This makes the overall process very much more complex. In addition, the temperature varies across the transformer itself. However a significant change in the FC over a period of months would indicate the probable development of a fault. The value of regular measurements of furfural concentrations in transformers seems clear.