矿物绝缘油中噻吩类非活性硫诱发绕组腐蚀的反应机理

Reaction mechanism of winding corrosion induced by thiophene inactive sulfur in mineral insulating oil

矿物绝缘油中腐蚀活性较强的硫化物已被证实会诱发油浸式电力设备绝缘故障,在绝缘油精炼过程中会被去除。部分非活性硫因其高效抗氧化性保留于矿物绝缘油中以提高油品的氧化安定性。然而,非活性硫在油浸式电力设备运行条件下的活化问题及其对绝缘性能造成的影响并未得到关注。文中针对矿物绝缘油中的典型非活性硫(噻吩类硫化物),聚焦油纸绝缘中非活性硫诱发绕组腐蚀的反应机理,采用材料物相分析方法探究噻吩类硫化物的热裂解产物,结合热裂解动力学分析方法,分析噻吩类硫化物在不同升温速率下的活化能变化规律,并开展噻吩类硫化物在油纸绝缘热老化作用下的试验研究。热裂解气相色谱、质谱以及热裂解傅里叶红外光谱结果表明,噻吩类硫化物(噻吩、苯并噻吩、二苯并噻吩)在热裂解过程中的主要活化产物为具有极强腐蚀性与挥发性的H 2 S。不同热裂解升温速率下,噻吩类硫化物的失重率规律基本一致,其中噻吩最容易发生热裂解,其次是苯并噻吩,最后为二苯并噻吩。在油纸绝缘低温过热条件下,由于体系能量的不断积累,会导致噻吩类硫化物发生活化进而生成低分子强腐蚀性硫化物,加剧油品腐蚀性,最终导致油纸绝缘发生硫腐蚀。

Strong corrosive active sulfur in the mineral insulating oil has been considered to be the main culprit to induce the insulation failures of oil-immersed power equipment.In order to protect the oil-paper insulation from sulfur corrosion,active sulfur is cleared in the refining process of crude oil.Some inactive sulfur with high antioxidant is still retained in the mineral oil to improve the oxidation stability of oil.However,the activation of inactive sulfur under the operating condition of oil-immersed power equipment is not gained attention.This paper focuses on the reaction mechanism of winding corrosion induced by non-active thiophene sulfide in mineral insulating oil.The thermal pyrolysis products of thiophene sulfide are investigated by the material phase analysis method,and the activation energy changes of thiophene sulfide at different heating rates are analyzed in combination with the pyrolysis kinetics analysis method,and the experimental study of inactive thiophene sulfide under the action of oil paper insulation thermal field is carried out.The results of gas chromatography,mass spectrometry and Fourier transform infrared spectroscopy show that the main activation product of thiophene sulfide(thiophene,benzothiophene,dibenzothiophene)during pyrolysis is H 2S,which is highly corrosive and volatile.The thermogravimetric and differential thermogravimetric curves of thiophene sulfides are basically the same at different pyrolysis rates,and thiophene is the most prone to pyrolysis,followed by benzothiophene and dibenzothiophene.Under the condition of low temperature superheating of oil paper insulation,due to the continuous accumulation of system energy,the inactive thiophene sulfide will be activated and then generate low molecular highly corrosive sulfide,which intensifies the corrosivity of oil products and leads to sulfur corrosion of oil paper insulation.