油中溶解气体分析（dissolved gas analysis,DGA）是现场电力变压器故障诊断最常用的方法。然而,油中溶解气体含量较容易受到变压器结构、容量、故障位置以及故障程度等因素的影响,从而降低了变压器故障诊断的可靠性。为了提升变压器故...油中溶解气体分析（dissolved gas analysis,DGA）是现场电力变压器故障诊断最常用的方法。然而,油中溶解气体含量较容易受到变压器结构、容量、故障位置以及故障程度等因素的影响,从而降低了变压器故障诊断的可靠性。为了提升变压器故障诊断正确率,该文提出了基于支持向量机（support vector machie,SVM）和遗传算法（geneti calgorithm,GA）优选的DGA新特征参量。首先,以28个DGA比值为输入,建立了基于SVM的变压器故障诊断模型;其次,采用GA同时对SVM参数和DGA比值进行优化,得到9个优选DGA比值作为变压器故障诊断用新特征参量。对IEC TC 10故障数据库的诊断结果表明：DGA新特征参量的故障诊断正确率为84%,较常用的DGA含量和IEC比值的诊断正确率提高10%~25%;并且无论采用哪种特征参量,支持向量机的诊断结果均优于神经网络诊断模型。最后,采用DGA新特征参量对国内117组变压器的故障诊断正确率达到了87.18%,再次验证了该方法的有效性。展开更多
In order to prepare special MRFs to satisfy the demands of tracked vehicle,two different carrier fluids were used to prepare MRFs.Preparation of MRF,which are based on carrier of special shock absorption fluid and 45#...In order to prepare special MRFs to satisfy the demands of tracked vehicle,two different carrier fluids were used to prepare MRFs.Preparation of MRF,which are based on carrier of special shock absorption fluid and 45# transformer oil,was finished.And characteristics of these samples were tested and analyzed.The results show that Tween-80 and Span-80 can improve the sedimentary stability,and the larger mass fraction can also increase the sedimentary stability.Using 45# transformer oil instead of special shock absorption fluid as a carrier of MRF,the shear yield stress remains nearly constant but the viscosity and the sedimentary stability are reduced.The MRF with diameter of 2.73 μm shows better sedimentary stability than that of the MRF with diameter of 2.30 μm,or 4.02 μm.Stearic acid obviously improves sedimentary stability and off-state viscosity,but has no function on the shear yield stress.In magnetic field of 237 kA/m,the shear yield stress of MRF based on special shock absorption fluid is 18.34 kPa and the shear yield stress of MRF based on 45# transformer oil is 14.26 kPa.展开更多
文摘In order to prepare special MRFs to satisfy the demands of tracked vehicle,two different carrier fluids were used to prepare MRFs.Preparation of MRF,which are based on carrier of special shock absorption fluid and 45# transformer oil,was finished.And characteristics of these samples were tested and analyzed.The results show that Tween-80 and Span-80 can improve the sedimentary stability,and the larger mass fraction can also increase the sedimentary stability.Using 45# transformer oil instead of special shock absorption fluid as a carrier of MRF,the shear yield stress remains nearly constant but the viscosity and the sedimentary stability are reduced.The MRF with diameter of 2.73 μm shows better sedimentary stability than that of the MRF with diameter of 2.30 μm,or 4.02 μm.Stearic acid obviously improves sedimentary stability and off-state viscosity,but has no function on the shear yield stress.In magnetic field of 237 kA/m,the shear yield stress of MRF based on special shock absorption fluid is 18.34 kPa and the shear yield stress of MRF based on 45# transformer oil is 14.26 kPa.
