Any pulse oscillator would be okay, you can use the grain synth as a pulse signal. you work from any electric hum sounds,the oscillator itself is fairly simple the interesting thing is what frequencies to add and substract from the hum, and how to change the sync of the pulse. For example, you can pass the signal through two filters, firstly a high pitch filter to make the most raw sound possible, to work from, and secondly a low filter to make the electric arc movements in a sweeping fasion. it's mostly a variation of phase sync and filter on a pulse osc.
The dynamics of the movement of the arc is that it slowly floats further away from the most stable path, and when it's too far, it snaps fast back towards another stable path, so the LFO to simulate the changes in phase resulting from the sound arriving at the use at different times, can be an slow lfo that is reset in a semi chaotic manner. perhaps add a spike on the filter when the lfo resets because a large arc bangs th more it changes it's course.
The same principle can be added for side arcs, some less loud and faster resetting small arcs added to the first sound.
The grain synthesis can only be used as an oscillator with phase control i think, alot of the sound of the arc must come from how the different pulses bounce in the room and arrive at the user, adding and substracting from each other in a complex frequency and phase variance.