Abstract
By the movement towards formation of standard international adjustment and the viewpoint of lightning protection，buildings using TN grounding systems are increasing. And there are many studies about the evaluation of grounding systems from viewpoints of lightning protection and earth fault protection. However there have been only a few studies of grounding systems from a viewpoint of the common-mode noise， which are induced to grounding system from inverter devices and disturb stable operation of electrical devises.For the present study，the author evaluated grounding system from the viewpoint of common-mode noises. The present paper shows the route of common-mode current in the power and grounding system with a PWM inverter and an induction motor，and describes the features of each grounding system，i. e. TT，TN，and IT grounding system.
