De link (o pôster fabrica dispositivos isolantes, então ele sabe o que fala):
What you are seeing when a console explodes is the failure of the insulators and surge protectors. Just like the product I work with, Starfleet Issue Protective Isolators would have a maximum rating.
During combat, lets face it... both sides are slinging massive amounts of power around trying to make the opposing side explode. Eventually one or more isolators are going to be overwhelmed and an arc is going to jump between the power-carrying components of the ship and the frame... and all that power has to go somewhere.
Sometimes it dissipates harmlessly, other times it causes things to fail catastrophically. Frankly given the power levels we are talking about I'm surprised there aren't more internal explosions.