A High Voltage Capacitor Element Model

Abstract

High voltage capacitors are becoming ever more prevalent on modern electrical power networks, as they offer simple means of power factor correction and voltage support, and are inherent to modern power electronic converter designs. Large capacitor banks comprise many modules, each of which contains an array of individual elements, across which voltage stresses and thermal conditions are shared. A module's partial degradation due to short-circuited elements can increase stresses on the insulation of those that remain, sometimes leading to cascading element failure. This paper presents a high voltage capacitor model, and then explores the distribution of voltage under healthy and short-circuit scenarios. It shows voltage distributions between elements within a capacitor module have nonlinearity due to a module's geometry, and are affected by series element failure.

A Capacitor Bank Simulation Model

“…With a more detailed approach to modelling and therefore larger foil-to-foil capacitances, nonlinearities due to unit housing are found to be less pronounced with more foil turns. This outcome tempers previous findings [2] and serves to highlight the importance of including detail in simulation models.…”

“…Knowledge of fault locations could thereby: aid maintenance; permit cascading fault interventions; and inform future designs. To these ends, this paper extends investigations on influence of housing on foil voltages in one unit [2] by exploring effects for multiple connected units, and where parallel strings of units share a common rack. It offers an illustrative background to high voltage capacitor banks in Section II before introducing a capacitor rack modelled in COMSOL Multiphysics ™ .…”