Fluke Fluke 4325162 User Manual

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

 

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. 

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 

2.  Turn central rotary switch to position " R

E

 3pole".