Transcript RPM Products Features

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
Joseph Ong
Aug 2005
Company Confidential 1
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
Joseph Ong
Aug 2005
Company Confidential 2
Earth Testing Methods
• Fall of Potential – 3 and 4 Pole Testing
• Resistivity
• Selective Testing
• Stakeless Testing
Joseph Ong
Aug 2005
Company Confidential 3
Earth Testing Methods (1)
Fall of Potential – Three and Four Pole Testing
Joseph Ong
Aug 2005
Company Confidential 4
Earth Testing Methods (1)
Fall of Potential – Three and Four Pole Testing
V
25m
RH
Joseph Ong
25m
RS
Aug 2005
I
RE
Company Confidential 5
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
Distance (m)
Joseph Ong
Aug 2005
Company Confidential 6
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
RE
a
Joseph Ong
...... mean value of soil resistivity (.m)
...... measured resistance ()
...... probe distance (m)
Aug 2005
Company Confidential 7
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:
Joseph Ong
Aug 2005
Company Confidential 8
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.
Joseph Ong
Aug 2005
Company Confidential 9
Earth Testing Methods (3)
Selective Measurement Method
Joseph Ong
Aug 2005
Company Confidential 10
Earth Testing Methods (3)
Selective Measurement Method
V
25m
RH
Joseph Ong
25m
RS
Aug 2005
A
I
RE
Company Confidential 11
Earth Testing Methods (3)
Principle: Selective earth measurements
Measured currentIIM
m
Measured
voltage
Probe
Auxiliary
earth
electrode
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.
R Display = R E3 !!
Joseph Ong
Aug 2005
Company Confidential 12
Earth Testing Methods (3)
Selective Measurement Method on High Tension Towers
Joseph Ong
Aug 2005
Company Confidential 13
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
Joseph Ong
Aug 2005
Company Confidential 14
Earth Testing Methods (3)
Joseph Ong
Aug 2005
Company Confidential 15
Earth Testing Methods (4)
Application: Function RE selective
SATURN GEO X,
SATURN GEO plus
Connection
to equipotential
bus bar
Equi Potential bus bar
Only the current
from the current
clamp is used for
calculation of RE.
sum
The precise value
of RE is on display!
Water pipe
RE Water pipe
IE Water pipe
Joseph Ong
RE
Earth electrode
Probe - (S)
(voltage reference)
Auxiliary earth - (H)
(injection of test current)
Isum = IE + IE Water pipe
RDisplay= U / IE =
RE
Aug 2005
Company Confidential 16
Earth Testing Methods (4)
Stakeless Measurement Method
Joseph Ong
Aug 2005
Company Confidential 17
Earth Testing Methods (4)
Stakeless Measurement Method
Joseph Ong
Aug 2005
Company Confidential 18
Earth Testing Methods (4)
Stakeless Measurement Method
Joseph Ong
Aug 2005
Company Confidential 19
Earth Testing Methods (4)
Stakeless earth loop measurements
I
I
Current
amplifier
Rx
R1
R2
Rm-1
Rm
Voltage
U
Rn
source
Rx
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.
Joseph Ong
Aug 2005
Company Confidential 20
Earth Testing Methods (4)
Principle: Stakeless earth measurements
Adapter –
for GEO X
only

Simply put both clamps
around conductor, cable,
pipe etc.

Clamps with a large variety
of openings are available.
black
red
Erder
Earth
electrode
• For all applications with at least
two earth electrodes...
e.g. high tension towers, meshed
grounding systems,
• telecom-cables ......
Joseph Ong
Aug 2005
> 10cm
Company Confidential 21
Earth Testing Methods (4)
Example: Stakeless earth measurement
Joseph Ong
Aug 2005
Company Confidential 22