Ground versus earth, there is a difference.

Investigations of injuries and fires caused by electrical circuits and equipment can result in incorrect conclusions when grounding systems are neglected. The term ground is loosely used in electrical jargon as any zero reference point for voltage measurement. Power systems are usually grounded to the earth. Other electrical systems are sometimes grounded to the same earth through a low impedance circuit. Residential grounding systems are described and a simple method is proposed for the investigator's use in evaluating the grounding system for potential shock or equipment damage hazards.