Earthing Arrangements

Question 1

What is the maximum allowed Ze value for a TN-C-S system?

Answer 1

0.35Ω

Question 2

What is the maximum allowed Ze value for a TN-S system?

Answer 2

0.8Ω

Question 3

What is the maximum allowed Ze value for a T-T system?

Answer 3

200Ω

Question 4

What is a PEN Conductor?
In which system would you find it?
What is its function?

Answer 4

• A PEN Conductor is a Protective Earth Neutral Conductor.
• You would exclusively find it in a TC-N-S system
• It provides the neutral and protective earth cable in a TC-N-S system. This is the seperate part of Terra-Combined-Neutral-Seperate

Question 5

Which of the supply systems has uses the steel wiring of the cable exclusviely for the earth connection?

Answer 5

TN-S system.
The line and the neutral cables are contained within the central core of the SWA cable.

Question 6

Which of the supply systems uses the general mass of the earth as a return path for earth leakage?

Answer 6

T-T System

Question 7

What is the figure used to denote the full earth fault loop?

Answer 7

Zₛ

Question 8

What is the figure used to denote the earth fault loop on the supplier side?

Answer 8

Zₑ

Question 9

What is the figure used to denote the earth fault loop on the consumer side?

Answer 9

R₁+R₂

Question 10

True or false:
We want the Zₛ to be as high as possible.

Answer 10

False.
We want the Zₛ to be as low as possible, to ensure that the highest possible amount of current flows to earth as easily as possible, ensuring a rapid disconnection time.

Question 11

What does TN-C-S stand for?
What does this mean?

Answer 11

Terra Neutral Combined Seperate.
This means that the Earth connection and the Neutral connection enter the property combined, but are then seperated at some point in the installation.

Question 12

What does PME stand for?
Which system is considered PME?
What does this mean in practice?

Answer 12

PME stands for Protective Multiple Earthing.
TN-C-S system is PME.
This means that the PEN conductor (containing both the supply neutral and earth) is earthed at multiple points on the supply side of the installation.

Question 13

What is the name of the kind of cable used in a TN-C-S system to house both the Earth and Neutral connections to the supply?

Answer 13

A PEN (combined protective and neutral) or CNE (combined neutral and earth) conductor.