Due to limitations in size and costing, motors and generators do not have surge withstand capabilities similar to other apparatus such as switchgear and transformers which are used in the electrical system. The two aspects of a transient surge, magnitude and rate of rise, can each create negative effects to the insulation system; and each require different protection components to mitigate their effects.

The magnitude of the transient surge effects the major insulation (phase to ground), and protection is accomplished with arrestors which limits the magnitude of the surge and it’s reflections.

The rate of rise of the transient surge effects the minor insulation (turn to turn), and protection is accomplished with surge capacitors which slow the rate of rise of the transient voltage wave front.

Other components such as phase CTs, differential CTs, and grounding transformers can located within the same enclosure.

Rotating machinery surge suppression units are intended to be located at the terminals of the motor or generator which is being protected such that lead impedance is held to a minimum.