The customer was rearranging the kitchen light switches and when he went to put the switches back into the box it created a ground fault and the breaker shut off. I removed the switches and found where the ungrounded conductors insulation has been stripped exposing copper and when he pushed the switch back it made contact to an equipment grounding conductor creating the ground fault and tripping the breaker. I was able to make the repair by extending the wire out and re-terminating the switches. Before restoring power I informed the homeowners that switch maybe damaged and I also checked for any ground fault conditions at the panel before reenergizing the circuit. After power was restored we found the switch to be damaged and the homeowner said he will find something else to replace it.