Final answer:
The three primary types of circuit protection devices used in aircraft circuits are circuit breakers, fuses, and ground fault circuit interrupters (GFCI), which help prevent thermal hazards and protect against shock by interrupting excess current or detecting ground faults.
Step-by-step explanation:
The three kinds of circuit-protection devices used most commonly in aircraft circuits are circuit breakers, fuses, and ground fault circuit interrupters (GFCI). Circuit breakers and fuses work by interrupting excessive currents to prevent thermal hazards.
The operation includes an automatic cut-off of power when the current exceeds a certain threshold, with circuit breakers being able to be reset after tripping, unlike fuses which need to be replaced. Fuses and circuit breakers are also essential for tackling issues that could cause high-voltage sparks, using insulating gas or gas jets to extinguish arcs in more powerful systems. Meanwhile, the GFCI is a device designed to protect from shock by quickly responding to changes in current due to a ground fault, which may signify electrical leakage through an unintended path, potentially posing a risk of electric shock.
The three-wire system enhances safety by utilizing a live (or hot) wire, a neutral wire, and an earth (or ground) wire. This system ensures that in the case of a fault, the current is directed safely to the ground rather than through a person's body. The neutral wire and the case of the appliance are grounded for added protection against shock and thermal hazards. Furthermore, some circuit-protection devices use induction to perform their basic function, which includes shielding against electromagnetic interference and ensuring the safe operation of the circuit.