Clip-On Transformer Errors Correction - Fluke 1625-2 User Manual

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:
Auxiliary earth electrode (ohmic):
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
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 " R
30 °... 60 ° inductive
>100 • Z
E
3pole".
E
Earth/Ground Tester
Advanced Operation
E
edw017.eps
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