Final answer:
Grounding is an essential safety feature in electrical systems that creates a zero-volt, low-resistance path to the earth, helping to prevent electric shock and fire hazards. It involves connecting the neutral wire and appliance cases to ground, with safety devices like circuit breakers and fuses providing additional protection.
Step-by-step explanation:
Grounding in Electrical Systems
Grounding is a crucial safety feature in electrical systems, particularly in alternating-current (AC) systems used in homes and businesses. The purpose of grounding is to create a low-resistance path directly to the earth, which can effectively fix a conductor at zero volts. This process minimizes the risk of electric shock and electrical fires by ensuring that excess current due to a fault, like a short circuit, has a safe path to the ground rather than passing through a person or causing overheating.
As depicted in Figure 23.30, the three-wire system has a protective mechanism involving the neutral wire being connected to ground at the voltage source and the user's location, forcing it to be at zero volts. This ground connection is typically represented by the color white on the neutral wire and is considered safe to touch. The inclusion of an earth/ground connection on the metal case of an appliance through the green earth/ground wire is also described, reinforcing the case to be at zero volts as well.
The live or hot wire carries the voltage and current needed to operate appliances. In case of a fault, like a short circuit to the grounded metal case of an appliance, when a person comes into contact with this case, the grounding system would divert the electricity to the earth. However, if the individual has low resistance to ground, for instance being wet with a 3.00 kΩ resistance, there is still a risk of electric shock, which is the reason why safety devices such as circuit breakers or fuses are essential to protect against thermal overload by interrupting the current flow in the live/hot wire when necessary.