Overcurrent, short circuit and
earth fault protection
Ch 12
233
Unit Application health and safety and electrical principles Outcome 5
Underpinning knowledge: when you have completed this chapter you should able to:
● state the need for protective devices
● list the factors which the selection protective device depends
● list the essential requirements for device designed protect against overcurrent
● state the action fuse under fault conditions
● state the need for ‘discrimination’ when number protective devices are fitted
● identify exposed and extraneous parts building
● state the path taken earth fault current
● state the need for RCDs and RCBOs
● state the meaning ‘Basic’ and ‘Fault’ protection
O 5
vercurre
are fitted
vercurre
ent
e
vercurre
v
ov
V
V
U
U W
W
6 6
2 2
C1
L1 C1
2
C3
4
5
6
To phase supply
