Use PROFITEST 0100SII to measure the internal mains resistance?

The mains impedance ZI is measured using the same measurement method as the loop impedance ZSchl. The current loop is formed via the neutral conductor N and not via the protective conductor PE as in the loop impedance measurement.

To determine the actual value, the PROFITEST 0100S-II must be connected to the outer conductor (L) and neutral conductor (N). For three-phase sockets, connect to all outer conductors one after the other.

Note: With the 2-pole adapter plugged in, measurement of the mains impedance is only possible in the ZSchl function!

When testing according to the current-voltage method, the voltage between the unloaded outer conductor and N is first determined. Then the PROFITEST switches a defined resistor into the measuring circuit and measures the voltage again, the current also has.

• The displayed resistance value must now be corrected by the operating measurement deviation of the device and by the temperature factor "K". Now the value corresponds to the condition of the plant and the value of the overcurrent protection device can be confirmed or rejected. In the PROFITEST, the table of assignment of the measured value to the IN of a fuse can now be called up by pressing the I key. In this table, the operating measurement deviation of the device is already taken into account, only the K-factor must still be calculated in
  

• If the net internal resistance is high, the maximum short-circuit current is reduced
  

• Consequently, this results in different values for the fuse to be used
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• In the case of a high internal mains resistance (> 1 Ω), it must be checked whether the entire installation has a high internal mains resistance or whether this value only occurs at this measuring point. In older systems, a high internal network resistance can occur without the system being faulty. However, if the high value is measured only at one measuring point, it must be assumed that there is a fault in the circuit