1. Earthing / Grounding Issues
Reasons for Earthing and Bonding
Detect fault current and fast removal of power source at fault
Prevent potential differences which may cause electrocution or sparks
Minimise the effect of lightning strikes
Prevent build-up of ESD
Minimise the effect of electrical interferences
Meet Explosion-Proof apparatus safety requirements
Reference: MTL website

2. Earthing / Grounding Issues
Ground / earth resistance and resistivity should be measured when:
Installing new ground systems and electrical equipment
Periodically testing of ground and lightning protection rods
Prior to design of ground protection systems

3. Earth Testing Methods
Fall of Potential – 3 and 4 Pole Testing
Resistivity
Selective Testing
Stakeless Testing

4. Earth Testing Methods (1)
Fall of Potential – Three and Four Pole Testing

5. Earth Testing Methods (1)
Fall of Potential – Three and Four Pole Testing

6. Earth Testing Methods (1)
Fall of Potential – Creating the ‘S’ Curve
The positioning of temporary electrode for the test is a critical issue
The distance between electrodes is dependant on the ‘pool of potential’ of the earth system under test
Distances of temporary electrode should be varied to plot values as an ‘S’ curve

7. Earth Testing Methods (2)
Resistivity Measurement
From the indicated resistance value RE, the soil resistivity calculates according to the equation :
E = 2 p . a . R E
E mean value of soil resistivity (W.m)
RE measured resistance (W)
a probe distance (m)

8. Principle: Wenner – Method
Measurement of specific earth resistance 
The measuring method according to Wenner determines the soil resistivity down to a depth of approx. the distance "a" between two earth spikes.
By increasing "a", deeper layers can be measured and checked for homogeneity. By changing "a" several times, a profile can be measured from which a suitable earth electrode can be determined.
According to the depth to be measured, "a" is selected between 2 m and 30 m. This procedure results in curves:

9. Earth Testing Methods (2)
Resistivity Measurement
Curve 1:As E decreases only deeper down, a deep earth electrode is advisable
Curve 2:As E decreases only down to point A, an increase in the depth deeper than A does not
improve the values.
Curve 3:With increasing depth E is not decreasing: a strip conductor electrode is
advisable.

10. Earth Testing Methods (3)
Selective Measurement Method

11. Earth Testing Methods (3)
Selective Measurement Method

12. Earth Testing Methods (3)
Principle: Selective earth measurements
Advantage: Distinct earth resistances within meshed ground systems can be measured without disconnection. Only clamp current Im is used for calculation of RE.
Important: The minimum clamp current is 0.5mA – if not, an error message is displayed. Im
Measured
voltage
Measured current IM
Probe
Auxiliary
earth
electrode
R Display = R E3 !!

13. Earth Testing Methods (3)
Selective Measurement Method on High Tension Towers

14. Earth Testing Methods (3)
Measurements on high tension towers
Applicable for nearly all metal constructions!
Example: Tower with four stands.
Important: Do not move the current injection point (E) during test!
All stands are tested in sequence with the split core transformer.
split
core
transformer
ring
earth
electrode

15. Earth Testing Methods (3)

16. Earth Testing Methods (4)
Application: Function RE selective
SATURN GEO X,
SATURN GEO plus
Only the current from the current clamp is used for calculation of RE.
The precise value of RE is on display!
Connection
to equi-
potential
bus bar
Equi Potential bus bar
sum
Water pipe
Earth electrode
Probe - (S)
Auxiliary earth - (H) RE
(voltage reference)
(injection of test current) R E
Water pipe I E
Water pipe I
= I
+ I
sum E
E Water pipe
RDisplay= U / IE = RE

17. Earth Testing Methods (4)
Stakeless Measurement Method

18. Earth Testing Methods (4)
Stakeless Measurement Method

19. Earth Testing Methods (4)
Stakeless Measurement Method

20. Earth Testing Methods (4)
Stakeless earth loop measurements I I
Current amplifier U
Voltage
source Rn Rx
Rn= m earth resistances in parallel
Assume that there are Rn resistances in parallel (e.g. in meshed ground systems, telecom, electric power distribution systems) earth connections are inter-connected. Thus Rn<<Rx is valid. Rn is negligible and the measuring loop resistance is mainly Rx. In this case the value on display of the
ground loop tester is exactly Rx.

21. Earth Testing Methods (4)
Principle: Stakeless earth measurements
Simply put both clamps around conductor, cable, pipe etc.
Clamps with a large variety of openings are available.
Adapter – for GEO X only
black
red
Erder
Earth electrode
> 10cm
For all applications with at least two earth electrodes... e.g. high tension towers, meshed grounding systems,
telecom-cables

22. Earth Testing Methods (4)
Example: Stakeless earth measurement