If the voltage is so high of the order of 20,000 to 30,000 volts or higher (which is high enough to ionize air between the power terminal and the nearest negative terminal/ground, chances are that you'll get a spark even before you touch the ground. However, once the terminal is grounded, current just flows down through to the ground and all you end up with is wastage of power...it does nothing. However, whether it sparks the way it does with a lightning bolt (a step leader followed by several return strokes that all apear as one single spark because it happens so quickly) or whether you end up with streaks of light as in st.elmo's fire will depend on the shape of your power terminal. Spherical surfaces have a lower surface charge density as compared to pointed surfaces so you're likely to get a plasma like formation with a pointed power terminal. In any case, once grounded, the current just flows down to the ground and that's the end of it - power wasted!