Expected Test Results

Question 1

What results would you expect to see from the measurement of any CPC?

Answer 1

A CPC test should produce a result with a very low resistance, although readings will be higher for longer lengths of cable or CPCs with a low CSA.

Question 2

What reading would provoke further investigation after determining the resistance of a CPC?

Answer 2

Generally anything above 1Ω

Question 3

When testing the earth bonding of an installation…

What should the resistance be between the service point and other extraneous-conductive-parts?

Answer 3

0.05Ω or less

Question 4

When testing the earth bonding of an installation…

What resistance value should the supplementary bonding conductors have?

Answer 4

0.05Ω or less

Question 5

True or false:
If you are recording results of a final ring circuit, and the highest result is a spur, you should not record this result for your R1+R2 value.

Answer 5

False.
When you are recording the value for the R1+R2 (for use in later tests), you are using the maximum R1+R2 value, as this is the highest value, all other values will be covered by this change in resistance.

Question 6

What four factors can contribute to a low insulation resistance reading?

Answer 6

1. Short-circuit
2. Defective insulation
3. Ingress of moisture
4. Ingress of foreign bodies

Question 7

Which four factors increase the resistance of conductors?

Answer 7

1. Material (Resistivity)
2. Area (CSA)
3. Length of conductor (Longer = more resistance)
4. Temperature (higher temp = higher resistance)

Question 8

True or false:
An RCD should trip at half of the design current for the circuit/ installation.

Answer 8

False.
If this happens then there is a fault somewhere.