GOALI: Optical Tomography Measurements of High Voltage Conduction and Breakdown Phenomena in Dielectrics

[9820515]该研究是麻省理工学院和EPRI之间的一个GOALI产学研合作项目，用于使用光学断层扫描测量高压绝缘、传导、预击穿和击穿特性的持续分析、计算和实验研究。该方法使用电场诱导双折射（克尔效应）与改进的敏感光学测量系统和新的先进数学公式，允许从光强度测量计算电场大小和方向在任何电极几何形状。由于大多数金属/介质系统的高压电荷注入和输运、预击穿和电击穿的物理特性是未知的，因此电场分布不能仅通过系统几何知识来计算。光学测量为确定电本构定律和学习电击穿过程的物理学提供了直接的方法，因此为提高介电系统的击穿强度提供了研究方法。拟议的持续研究计划涉及研究生和本科生以及EPRI人员，试图进一步了解高场应力气体，液体和固体电介质中的电荷注入，传导，老化，降解，预击穿和击穿机制，使用新的现代光学，电子和计算机仪器，在材料内部提供“眼睛”，以看到以前无法测量的预击穿和击穿场以及电荷分布。具体建议的工作任务是：1)扩展并完成克尔效应的数学公式，在克尔效应中，外加电场的大小和方向沿任何三维几何形状的光路变化；开发计算算法，将测量光信号转换为电场分布；并用实验验证分析结果；2)开发一种计算机接口摄像系统，该系统配备分布在一个区域内的光学阵列探测器，可以在没有机械运动的情况下自动获取和处理敏感的kerr测量数据；3)在良好控制和监测的测试池中，对体积内和电双层界面内的各种液体/固体材料组合进行敏感的克尔电光场和电荷映射测量，作为直流电压幅值和极性，交流电压幅值和频率，界面方向与外加电场，温度，水分，电导率，水分和微量添加剂浓度的函数；4)扩展灵敏的kerref效应技术，在脉冲、斜坡和其他时变外加电场中对弱双折射介质进行测量；5)将建模、光学测量和介电测量的结果与更好地理解介电介质中的高压导电、预击穿和击穿现象联系起来，以便可靠地将高压设备的操作扩展到更高的电压；6)构建一个紧凑的光学传感器测量系统，该系统将在EPRI人员和承包商的帮助下应用于运行变压器的电场和空间电荷测量

9820515ZahnThe proposed research is a GOALI industry-university collaborative projectbetween MIT and EPRI for the continued analytical, computational, andexperimental study using optical tomography measurements of high voltageinsulation, conduction, prebreakdown and breakdown characteristics indielectrics. The methodology uses electric field induced birefringence(Kerr effect) with an improved sensitive optical measurement system and anew advanced mathematical formulation that allows calculation of electricfield magnitude and direction in any electrode geometry from opticalintensity measurements. Because the physics of high voltage chargeinjection and transport, prebreakdown and electrical breakdown are not knownfor most metal/dielectric systems, the electric field distribution cannot becalculated from knowledge of system geometries alone. Optical measurementsprovide a direct approach to determining electrical constitutive laws andlearning the physics of the electrical breakdown process and so offers aresearch methodology for major advances in increasing the breakdown strengthof dielectric systems. The proposed continuing research program involves both graduate andundergraduate students together with EPRI personnel to try to furtherunderstand charge injection, conduction, aging, degradation, prebreakdownand breakdown mechanisms in high field stressed gaseous, liquid, and soliddielectrics using new modern optical, electronic, and computerinstrumentation to give "eyes" inside materials to see prebreakdown andbreakdown field and charge distributions that could not be measured before.Specific proposed work tasks are 1) Extend and complete the mathematicalformulation of the Kerr effect where the applied electric field magnitudeand direction change along the light path for any three dimensionalgeometry; develop computational algorithms to convert measured opticalsignals to electric field distributions; and to verify analysis withexperiments; 2) Develop a computer interfaced camera system with an opticalarray detector distributed over an area to automate sensitive Kerrmeasurement data acquisition and processing without mechanical motion; 3)Perform sensitive Kerr electro-optic field and charge mapping measurementsin a well controlled and monitored test cell for various liquid/solidmaterial combinations in the volume and within the electrical double layernear interfaces as a function of DC voltage amplitude and polarity, ACvoltage amplitude and frequency, direction of interface with respect toapplied electric field, temperature, moisture, conductivity, andconcentration of moisture and trace additives; 4) Extend the sensitive Kerreffect technique and perform measurements for weakly birefringentdielectrics in pulsed, ramped, and other time varying applied electricfields; 5) Relate the results of the modelling, optical measurements, anddielectrometry measurements to a better understanding of high voltageconduction, prebreakdown and breakdown phenomena in dielectrics in order toreliably extend the operation of high voltage apparatus to higher voltages;and 6) Construct a compact optical sensor measurement system that with thehelp of EPRI personnel and contractors will be applied to electric field andspace charge measurements in an operating transformer.***