Breaker And Fuse Discrimination

Question 1

Intro

Answer 1

• Breakers and fuses do not protect the item being operated.
• If tripped or blown, a problem already exists in the item being operated.
• Breaker and fuses are used to protected the power supply only.

Question 2

Breaker discrimination

Answer 2

• First breaker to trip is the MCCB.
• Last breaker to trip is the Supply Breaker.
• Breaker nearest the fault is the first.
• Breaker furthest from the fault is the last.

Question 3

Fuse discrimination

Answer 3

•Fuse nearest the fault is the first.
•Fuse furthest from the fault is the last.
•Multiple fuse panel in a circuit
-440V discrimination uses a ratio of 3:2
-115V discrimination uses a ratio of 2:1
•Mess decks kettle fault CANNOT trip a generator supply breaker.