Fluke 1625-2 User Manual - Page 37

Clip-On Transformer Errors Correction, Measuring process

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Earth/Ground Tester Advanced Operation Measuring Earthing Impedance with 55 Hz (R*) For the calculation of short circuit currents in power supply plants, the complex earthing impedance is important. Direct measurement is possible under the following conditions: Phase angle at 50 Hz: 30 °... 60 ° inductive Auxiliary earth electrode (ohmic): Measuring process: >100 • ZE The measurement of the earthing impedance (R*) is only possible if it is activated by putting in a personalized user's code (see "Change of Setup Data with Personalized Code"). If this measuring function is activated, in every measurement of the four RE positions, the earthing impedance R* is displayed before all other measured values. Clip-On Transformer Errors Correction If the measurement of an earthing resistance by means of a clip-on transformer results in a significantly different value as if measured without the clip-on, the deviation may be due to the tolerances of the clip-on current transformer. This error can be corrected by fine tuning the clip-on transformation ratio (basic settings 1000:1). This correction applies to the transformer current range it was performed with. For other ranges a different correction may be necessary. 1. Connect a low Ohm resistor (approximately 1 Ohm - in the range you want to correct) as shown in Figure 8. Figure 8. Correcting Clip-on Transformer Errors 2. Turn central rotary switch to position " RE 3pole". edw017.eps 29

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Earth/Ground Tester
Advanced Operation
29
Measuring Earthing Impedance with 55 Hz (R*)
For the calculation of short circuit currents in power supply plants, the complex earthing
impedance is important. Direct measurement is possible under the following conditions:
Phase angle at 50 Hz:
30
°
... 60
°
inductive
Auxiliary earth electrode (ohmic):
>100 • Z
E
Measuring process:
The measurement of the earthing impedance (R*) is only possible if it is activated by
putting in a personalized user's code (see "Change of Setup Data with Personalized
Code"). If this measuring function is activated, in every measurement of the four R
E
positions, the earthing impedance R* is displayed before all other measured values.
Clip-On Transformer Errors Correction
If the measurement of an earthing resistance by means of a clip-on transformer results in
a significantly different value as if measured without the clip-on, the deviation may be due
to the tolerances of the clip-on current transformer. This error can be corrected by fine
tuning the clip-on transformation ratio (basic settings 1000:1). This correction applies to
the transformer current range it was performed with. For other ranges a different
correction may be necessary.
1.
Connect a low Ohm resistor (approximately 1 Ohm - in the range you want to correct)
as shown in Figure 8.
edw017.eps
Figure 8. Correcting Clip-on Transformer Errors
2.
Turn central rotary switch to position "
R
E
3pole".