水和盐水对GIS用三元乙丙密封圈热老化特性的影响

Influence of Water and Saline on Thermal Aging Characteristics of EPDM Seal Rings in GIS

气体绝缘金属封闭开关设备(gas insulated metal-enclosed switchgear,GIS)密封圈因受到水或含有盐离子的水侵蚀老化,引起SF 6气体泄漏的故障时有发生,威胁设备安全运行。为此,研究水(湿)和盐水(湿盐)对三元乙丙橡胶密封圈热老化特性的影响,对GIS三元乙丙橡胶密封圈分组进行热压缩、湿热压缩和湿盐热压缩等多因子加速老化试验,在老化10 d、20 d时测量密封圈的压缩永久变形和硬度变化率,用扫描电子显微镜观察试样外侧面形貌,用电子探针测量元素含量。结果表明:水对GIS密封圈表面有腐蚀作用,加剧了断链和氧化反应,使其产生裂纹,压缩永久变形增大;湿盐热压缩老化中湿和盐联合作用,盐水对密封圈有强腐蚀作用,试样老化以断链反应为主,使密封圈产生多孔,盐水沿孔洞进入橡胶,橡胶吸水溶胀,压缩永久变形反而较小,硬度变化率较小。湿热压缩老化、湿盐热压缩老化在压缩率20%时,与压缩率25%、30%相比,密封圈压缩永久变形更大,密封性能下降较严重。

SF 6 leakage faults occur occasionally due to erosion aging by water or water with saline ions to the seal ring of the gas insulated switchgear(GIS),which threats the safety of power equipment.Therefore,this paper studies the influence of water(damp)and saline(damp and salt)on the thermal aging characteristics of the ethylene propylene diene monomer(EPDM)seal ring.By carrying out multi-factor accelerated tests on the GIS EPDM seal ring including thermocompression test,damp and hot compression test and damp salt and hot test,it measures compression set(CS)and hardness change rate(HCR)of the seal ring after ten days and twenty days of aging.Afterwards,it uses the scanning electron microscopy(SEM)to observe the outside surface morphology and the electronic probe(EPMA)to measure element contents.The test results indicate that the water has corrosive effect on the GIS seal ring,accelerating chain scission and oxidation reaction,causing cracks,and increasing CS.During damp salt and hot compressing aging,damp and salt plays synergistic effect,and the saline has a strong corrosive effect on the seal ring.Aging of the sample is dominated by chain scission,which causes the seal ring producing holes on the surface through which the saline enters into the rubber.The rubber absorbs the water and swells,causing CS and HCR rather smaller.As the compression rate is 20%,CS of the seal ring is larger than that when the compression rates are 25%and 30%,and the sealing property declines seriously.