“Large” HV Structures: Transient Analysis of Voltage Distribution from First Principles

One of the intrinsic properties of HV devices is that, at fast transitions, voltage distribution along their physical structures is largely governed by parasitics. Examples range from garlands of insulators to HV dividers and their components, to machine and transformer windings. Traditionally, analyses of such structures are made with use of equivalent circuits (EC). Such analyses have long history; they are well developed and are fast and powerful. The main problem for numerical analysis is derivation of circuit parameters. The latter actually calls for field analysis, from which stresses on components and insulation, as well as parasitic parameters, can be determined from first principles. HV constructions may be "long" compared to characteristic wavelength. Then wave formulations of Maxwell equations need to be invoked. In this paper, we exclude such cases from consideration. We limit analysis to an example of a mixed resistive-capacitive divider. Modeling is done with COMSOL Mutiphysics. Conductive problem is solved; both conduction and displacement currents are accounted for. Similar to circuit analysis with EC, it is seen that voltage distribution along the divider can be far from linear; moreover, field along the resistor body can vary greatly. Results of field and EC simulations are compared.