This chapter introduces a novel technique for electric field grading and control in power apparatus with functionally graded material (FGM). FGM is characterized by the spatial distribution of dielectric permittivity and/or electrical conductivity in a solid insulator, which is expected to control the surrounding electric field distribution in power apparatus such as gas-insulated switchgears (GIS), epoxy molded transformers, and bushings. 12.1 IntroductionInnovation leading to higher performance and increased reliability of electrical power apparatus can be brought about through novel electrical insulating materials. For example, SF6 gas-

insulated switchgear has contributed to the drastic reduction in size and footprint of such apparatus and, therefore, substations. However, because of the high sensitivity of SF6 gas to electric field stress, the insulation design and configuration of gas-insulated power apparatus is complicated and costly to ensure appropriate electric field control, relaxation, and optimization. Thus, the development of novel and innovative approaches to electrical insulating materials to overcome the above issues is one of the most important tasks for future electrical power engineering.