Final answer:
Open electrical service conductors require adequate clearance from various structures to prevent shock and thermal hazards. Plastic insulation on wires prevents shock hazards. Ordinary circuit breakers and fuses are ineffective against shocks but prevent thermal hazards; GFIs are used for shock protection.
Step-by-step explanation:
The question relates to electrical safety clearance requirements for open electrical service conductors and multi-conductor cables that are not housed in a raceway or covered by an overall outer jacket. It is important to maintain adequate clearance to prevent accidental contact with electricity, which can lead to shock hazards and thermal hazards. The plastic insulation on live/hot wires serves to prevent shock hazards by insulating the conductor and mitigating the risk of electrical current passing through a person who might come into contact with the wires.
Ordinary circuit breakers and fuses are designed to prevent thermal hazards by interrupting excessive currents that can cause overheating and potentially fires. However, they are ineffective in preventing shocks because they do not react quickly enough to the very small current changes typical of human body contact with live parts. Ground Fault Interrupters (GFIs) are used to prevent shock hazards because they are designed to trip when there is a difference in current between the live/hot and neutral wires, which can occur when electricity is leaking to ground through an unintended path, such as a human body.