ABSTRACT
This chapter is concerned with the electrical properties of polymers employed as insulation. The emphasis is on extruded polymers. In Chapter 5, we demonstrated that the physicochemical properties of polymers employed as electrical insulation
6.1 Introduction .................................................................................................. 143 6.2 Volume Resistivity (VR) ............................................................................... 145 6.3 Insulation Materials Response at Operating Stress ...................................... 146
6.3.1 Polarization ....................................................................................... 146 6.3.2 Dielectric Constant/Permittivity/SpeciŽc Inductance
Capacitance .................................................................................149 6.3.3 Dielectric Losses ............................................................................... 151 6.3.4 Dispersion ......................................................................................... 151 6.3.5 Mineral Filled Systems and Interfacial Polarization ........................ 153 6.3.6 Conduction ........................................................................................ 154 6.3.7 Cable Response ................................................................................. 155 6.3.8 Paper/Fluid Systems ......................................................................... 155 6.3.9 Conclusions ....................................................................................... 156
6.4 Insulation Response at High Stress .............................................................. 156 6.4.1 Introduction ...................................................................................... 156 6.4.2 Dielectric Strength ............................................................................ 157 6.4.3 Test Methods ..................................................................................... 158 6.4.4 Breakdown and Failure ..................................................................... 160
6.4.4.1 Intrinsic Strength ............................................................... 160 6.4.4.2 Breakdown Strength Considerations.................................. 160 6.4.4.3 Data Analysis ..................................................................... 162
6.4.5 Partial Discharge .............................................................................. 163 6.4.5.1 What Happens in Voids ..................................................... 163 6.4.5.2 What Happens to the Insulation ......................................... 164 6.4.5.3 Key Partial Discharge Phenomena Parameters ................. 165
6.5 Summary ...................................................................................................... 166 References .............................................................................................................. 167
are determined by the chemical structure of the polymer; the nature of their chemical bonds and their geometry. The fundamental properties of the polymers employed as insulation and as shields were reviewed therein.
