Modelling of low current surface discharges using PSCAD

In this work, low current discharges (less than 10 mA) are classified into two forms: unstable discharges and stable arcs. Such discharges may present on outdoor insulation surfaces due to the complex conditions created by the electrical fields, moisture and insulation geometry. The discharges can lead to heating and chemical effects; potentially degrading the insulation surface and accelerating further damage. Modeling of such discharges has been conducted, and a simulation including the test circuit arrangement for the various conditions has been created in the ‘PSCAD’ software. The outcome of current and voltage curves from the simulation show good correlation with experimental data for the range of unstable discharges and stable arcs studied. The simulation work agrees with experiment work in that a low current discharge will become more detrimental if it is transformed from an unstable state to a stable arc, or if the stable arcs are physically compressed in length by any mechanism.