Current trends of production development as regards to the electrical insulation materials for HV electrical machines winding insulation: test results on long-term electrical strength

Mica paper is a basic component of HV insulation system. As the paper itself has a low mechanical strength to use it for stator winding insulation of HV electrical machines the reinforcement backing is required. The most widely spread reinforcing backing is glass fabric. Recently they have started to use polyester film for this purpose. The interest to polyester film is brought about by the fact that using polyester film backed mica tapes it is possible to decrease of insulation thickness as the film is at one time both a dielectric and a reinforcement material. There is some positive experience of applying film mica electrical insulation tapes for wire insulation in HV electrical motors. However to use this experience when producing main insulation for stator winding of HV electrical motor it is necessary to study the issues of polyester film stability to the exposure of long-term voltage of alternating frequency. Given below there are test results of different Resin Rich and VPI mica insulation systems made of glass fabric, polyester film and non-woven polyester paper. The tests were done on serial OAO (JSC) “Elinar Holding Company” electrical insulation mica tapes