Earthing / Grounding Issues

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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
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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

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Earth Testing Methods

• Fall of Potential 3 and 4 Pole Testing
• Resistivity
• Selective Testing
• Stakeless Testing

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

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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)
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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
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Earth Testing Methods (2)
Resistivity Measurement
Curve 1As ?E decreases only deeper down, a deep
earth electrode is advisable Curve 2As ?E
decreases only down to point A, an increase in
the depth deeper than A does not improve the
values. Curve 3With increasing depth ?E is not
decreasing a strip conductor electrode is
advisable.
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Earth Testing Methods (3)
Selective Measurement Method
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Earth Testing Methods (3)
Selective Measurement Method
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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.
R Display R E3 !!
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Earth Testing Methods (3)
Selective Measurement Method on High Tension
Towers
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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
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Earth Testing Methods (3)
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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
Earth electrode
Auxiliary earth - (H)
Probe - (S)
Water pipe
RE
(injection of test current)
(voltage reference)
R
E
Water pipe
I
I
I
I
E
Water pipe
sum
E
E Water pipe
RDisplay U / IE RE
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Earth Testing Methods (4)
Stakeless Measurement Method
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Earth Testing Methods (4)
Stakeless Measurement Method
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Earth Testing Methods (4)
Stakeless Measurement Method
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Earth Testing Methods (4)
Stakeless earth loop measurements
I
I
Current amplifier
Voltage source
U
Rx
Rn
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 RnltltRx 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.
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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
Earth electrode
gt 10cm

• For all applications with at least two earth
  electrodes...e.g. high tension towers, meshed
  grounding systems,
• telecom-cables ......

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Earth Testing Methods (4)
Example Stakeless earth measurement