Fluke 1625-2 User Manual - Page 35

ER ER ER ER ER, Advanced Operation

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Earth/Ground Tester Advanced Operation As all four pylon stubs are connected to the foundation earth of the pylon, the measuring current Imeas is divided into five components according to the present resistances involved. One part flows via pylon construction to the overhead earth wire and further to the parallel circuited pylon earthing resistances. The other four current components (I1... I4) flow via each individual pylon foot. The addition of all currents result in a current IE going through the earthing resistance, for example, the resistance of the "composite" earth electrode to the soil. If the current transformer is fixed to each pylon stub, one after the other, four resistances have to be measured which show a behavior inversely proportional to the corresponding current components I1 ... I4. The feeding point of the measuring current is to be left unchanged to avoid a change in the current distribution. Accordingly, these equivalent resistances are displayed as: REi = U meas li Therefore the earthing resistance RE of the pylon is determined as a parallel circuit of the individual equivalent resistances: RE = 1 1 11 1 RE1 + R E2 + RE3 + RE4 1. Turn central rotary switch to position "RE 3pole" or RE 4pole". The instrument is wired according Figure 7 and messages on the display. A flashing of the sockets symbols or , points to an incorrect or incomplete connection of the measuring lead. 2. Apply current transformer to the pylon stub. Make sure that the transformation ratio set on the instrument corresponds to the current transformer used. Change settings if necessary (see "Changing of All Data Settings with Personalized CODE"). 3. Press "START TEST" button. Now a fully automated test sequence of all relevant parameters like auxiliary earth electrode, probe and earth electrode resistances, is implemented and finishes with the display of the result RE. 4. Read out measured value RE. 5. Call RS and RH with "DISPLAY MENU". 27

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Earth/Ground Tester
Advanced Operation
27
As all four pylon stubs are connected to the foundation earth of the pylon, the measuring
current
I
meas
is divided into five components according to the present resistances
involved.
One part flows via pylon construction to the overhead earth wire and further to the
parallel circuited pylon earthing resistances.
The other four current components (
I
1
... I
4
) flow via each individual pylon foot.
The addition of all currents result in a current
I
E
going through the earthing resistance, for
example, the resistance of the "composite" earth electrode to the soil.
If the current transformer is fixed to each pylon stub, one after the other, four resistances
have to be measured which show a behavior inversely proportional to the corresponding
current components
I
1
... I
4
. The feeding point of the measuring current is to be left
unchanged to avoid a change in the current distribution.
Accordingly, these equivalent resistances are displayed as:
li
U
R
meas
Ei
=
Therefore the earthing resistance R
E
of the pylon is determined as a parallel circuit of the
individual equivalent resistances:
4
3
2
1
1
1
1
1
1
E
E
E
E
E
R
R
R
R
R
+
+
+
=
1.
Turn central rotary switch to position “
R
E
3pole" or
R
E
4pole". The instrument
is wired according Figure 7 and messages on the display.
A flashing of the sockets symbols

or
, points to an incorrect or
incomplete connection of the measuring lead.
2.
Apply current transformer to the pylon stub. Make sure that the transformation ratio
set on the instrument corresponds to the current transformer used. Change settings if
necessary (see “Changing of All Data Settings with Personalized CODE”).
3.
Press “START TEST” button.
Now a fully automated test sequence of all relevant parameters like auxiliary earth
electrode, probe and earth electrode resistances, is implemented and finishes with
the display of the result R
E
.
4.
Read out measured value R
E
.
5. Call R
S
and R
H
with “DISPLAY MENU”.