How do you counter the induced voltage spark during the generator?

By creating a rotating electric field. The generator has two main sets of windings - the field windings (the spinning ones on the rotor usually) and the stator windings(the stationary part connected to the grid). The field windings are electrified to create an electromagnet out of the rotor. Spinning the rotor creates a rotating electric field, which induces a voltage on the stator windings.