Electric Stresses

The determination of electric field strengths is of fundamental importance for quantification and control of high voltage stresses. First, the theoretical equations describing electrical fields are summarized. The following sections describe that different technical stresses due to high DC, AC and impulse voltages result in the formation of different types of fields. For simple configurations, steady-state and quasi-stationary (slowly varying) fields can be calculated or estimated by analytical methods. Here, simple insulation systems with a single homogeneous dielectric and insulation systems made of different layered dielectrics are distinguished. There are fundamental differences for quasi-stationary fields at AC and impulse voltages and for the steady-state DC case. So-called field grading methods can be used for reducing electrical stresses. Complex insulation systems, which cannot be approximated by simple geometries and cannot be evaluated analytically, require numerical calculation. Fast changing electromagnetic phenomena, such as traveling waves on lines, need special consideration.