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

9820515Zahn 拟议的研究是 MIT 和 EPRI 之间的 GOALI 产学合作项目，用于利用光学断层扫描测量电介质中的高压绝缘、传导、预击穿和击穿特性进行持续分析、计算和实验研究。 该方法使用电场引起的双折射（克尔效应）以及改进的灵敏光学测量系统和新的先进数学公式，允许根据光强度测量计算任何电极几何形状中的电场强度和方向。 由于大多数金属/电介质系统不知道高压电荷注入和传输、预击穿和电击穿的物理原理，因此不能仅根据系统几何形状的知识来计算电场分布。 光学测量提供了确定电本构定律和了解电击穿过程物理原理的直接方法，因此为提高介电系统击穿强度的重大进展提供了研究方法。拟议的继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，为材料内部提供“眼睛”，以观察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，其中对于任何三维几何形状，施加的电场大小和方向沿光路变化；开发计算算法将测量的光信号转换为电场分布；并通过实验验证分析； 2) 开发一个计算机接口的相机系统，该系统具有分布在某个区域的光学阵列探测器，可以自动采集和处理敏感的克尔测量数据，而无需机械运动； 3) 在良好控制和监测的测试单元中，对体积内和电双层近界面内的各种液体/固体材料组合进行灵敏的克尔电光场和电荷映射测量，作为直流电压幅度和极性、交流电压幅度和频率、界面相对于施加电场的方向、温度、湿度、电导率以及水分和微量添加剂浓度的函数； 4) 扩展灵敏的克尔效应技术，并在脉冲、斜坡和其他随时间变化的施加电场中对弱双折射电介质进行测量； 5) 将建模、光学测量和介电测量的结果与更好地理解电介质中的高压传导、预击穿和击穿现象联系起来，以便可靠地将高压设备的运行扩展到更高的电压；6) 构建一个紧凑的光学传感器测量系统，在 EPRI 人员和承包商的帮助下，该系统将应用于运行变压器中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.***