Numerical Investigations of Superimposed DC Voltages with Overvoltages and their Effect on the Insulating Gas Air

For reasons of cost and free availability, the insulating gas air cannot be omitted in high-voltage technology. Particularly in High Voltage Direct Current (HVDC) transmission systems, new types of pulses occur in fault cases due to converter technology, which stresses the insulating gas air. In addition to the well known lightning impulses (LI) and switching impulses (SI), very slow front overvoltages occur in high-voltage DC transmission systems. Therefore, in this work, superimposed stresses are used to numerically investigate the effects on air. The three different pulse shapes are implemented in an already verified plasma-physical model. The question arises to what extent the transient discharge current induced in the electrode by the direct voltage stress changes as a result of the pulse. By numerical simulation it can be shown that after the pulse has decayed, the induced transient discharge current of the electrical discharge converges against the current of the DC voltage load.