EL0018 - Fault Loop Impedance

Match the following R_PHE values for the given cable and CB sizes

• 0.6 Ω

• 1.5mm² 10A Type C CB

• 1.2 Ω

• 1.5mm² 16A Type C CB

• 1.0 Ω

• 2.5mm² 20A Type C CB

• 2.0 Ω

• 4mm² 32A Type C CB

Answer explanation

AS 3000 Table 8.2

Select the maximum permissible disconnection time for a circuit-breaker supplying an oven

• 5 Seconds

• 0.4 Seconds

• 0.3 Seconds

Answer explanation

1.5.5.3 d) ii 5s for submains and fixed or stationary equipment

Select the maximum value of earth fault-loop impedance (Zs AT 230 V) for a submain circuit supplied via 80A HRC fuse

• 0.4

• 0.7

• 0.6

Answer explanation

AS 3000 Table 8.1.

Submains have a disconnection time of 5 seconds. Protected by a HRC Fuse

What table from AS 3008 gives the values for Reactance (Xc) of a 3 phase 95mm² multicore XLPE cable?

Answer explanation

AS 3008 Table 30

Reactance (Xc) for all cables

What table from AS 3008 gives the values for Resistance (Rc) of a 3 phase 95mm² multicore XLPE cable?

Answer explanation

AS 3008 Table 35

Resistance (Rc) for multicore circular conductors

What is the maximum route length for a 1.5mm² cable protected by a 16A Type C CB?

(Hint: Use Table B1 in AS 3000)

Answer explanation

AS 3000 Table B1 - 1.5mm 16A Type C CB = 51m max route length

What is the maximum route length for a 4mm² cable protected by a 25A Type C CB?

(Hint: Use Table B1 in AS 3000)

Answer explanation

AS 3000 Table B1 - 4mm 25A Type C CB = 67m max route length