矿用干式变压器Nomex绝缘老化机理研究

The insulation aging is one of the main failure forms of the mining flameproof dry-type transformer, moreover, it is one of the main causes resulted in The devastating accident of mine coal. In coal mine, the most fundamental factor causing the insulation degradation in mining flameproof dry-type transformer is special environmental condition. Therefore, it is of significant social meaning to explore the decomposition mechanism of the Nomex insulation for preventing coal mine from the mine fire and gas explosion accident. Because of particularity of environmental condition in coal mine, there is little study on insulation degradation mechanism of the mining flameproof dry-type transformer. The project aims at building a multi-stress aging test system to simulate the special environmental condition of coal mine, confirming stress factors and aging strategies, and focusing on researching degradation mechanism of Nomex insulation for the mining flameproof dry-type transformer under the interaction of electrical stress, thermal stress, mechanical stress and environmental stress. It also searches inner relationship between physical, chemical change and insulation electrical property, mechanical property. In addition, combined with the polymer theory, the aging process and decomposition mechanism of the Nomex will be explored from the micro perspective. And then decomposition dynamics model of the Nomex will be established to determine the correlation of stress factors on accelerated aging of the insulation. The quantitative relationship between intensity of stress factors and aging rate of Nomex insulation will be analysed,which will provide theoretical basis for modification research of Nomex insulation in dry-type transformer.

矿用干式变压器绝缘老化是其主要故障形式，也是导致煤矿重大安全事故的主要原因之一。引起变压器绝缘老化的原因很多，其中矿井特殊环境是造成其绝缘老化的关键因素。因此研究Nomex绝缘的老化机理对防止矿井火灾和瓦斯爆炸事故的发生具有重要意义。由于矿井环境特殊，关于矿用干式变压器绝缘老化机理的研究在国内外一直少有人问津。本项目通过建立能够模拟矿井环境条件的多应力因子老化试验系统，确定应力因子强度和老化策略，重点研究矿用干式变压器Nomex绝缘在电、热、机械及环境等应力联合作用下的老化机理，探索老化过程中绝缘理化特性与其绝缘电气性能、机械性能的内在关系；从微观角度出发，结合高分子理论从本质上揭示Nomex绝缘的劣化过程和分解机理；通过建立Nomex纸分解动力学模型，分析其分解速率与应力因子的相关性，并确定应力因子强度与Nomex绝缘老化速度之间的量化关系，为干式变压器Nomex绝缘改性研究提供理论依据

矿用干式变压器作为煤矿井下供电系统的动力中心，其工作可靠性直接关系到整个井下的供电安全。随着国民经济对煤炭需求量的增加和煤炭生产技术的进步，矿用干式变压器容量、电压等级和供电距离不断增大，其故障发生率也大幅上升。在矿井干式变压器故障中，因绝缘薄弱处的老化和失效造成的绝缘故障占很大比重。本项目重点针对电-热-水分多应力下矿用干式变压器Nomex绝缘纸的老化和故障机理进行研究，搭建了多因子联合老化实验平台，获得了Nomex绝缘纸微观形貌、聚合度、热稳定性、空间电荷分布、介电特性以及放电特性的演化规律，利用多个特征量表征Nomex绝缘纸老化程度；研究了老化因子（水分、温度、电压）对Nomex老化的影响规律，据此建立了聚合度-绝缘寿命的数学模型，可用于Nomex绝缘纸多因子老化寿命评估。对比分析不同初始水分含量下Nomex绝缘纸频域介电特性的变化趋势，发现提升水分含量能够显著提高Nomex绝缘纸的水解速率，绝缘纸的复介电常数实部与介质损耗因数均出现下降现象。分析了电压、温度和水分对绝缘纸聚合度的影响，发现水分、电压和温度均会加速Nomex绝缘纸的老化，在水分的作用下，温度对Nomex绝缘纸老化更敏感。通过热分析试验探究了不同老化程度绝缘纸动力学参数的变化规律，发现在整个老化过程中，随着聚合度的减小，热焓值与聚合度成指数关系，故可考虑将热焓值作为评判变压器Nomex绝缘纸老化的参量。对不同老化程度下的典型放电进行研究，获得了老化周期、老化因子及环境对局部放电特征参量的影响规律，发现放电参量与老化状态密切相关，为Nomex绝缘纸老化评估提供了实验数据。对不同老化周期Nomex绝缘纸试样进行空间电荷测试，并提取老化特征量，发现陷阱能级密度和深度变化可以用作判断Nomex绝缘老化程度的依据。本项目研究成果为矿用隔爆型干式变压器绝缘状态评估、寿命评估和故障诊断等建立了理论和实验基础。