Measuring Earthing Impedance with 55 Hz R

1625

Users Manual

Time average measurement:

If there is a warning "measured value unstable" (see "Description of displays", Procedure of Measurement) after a test sequence, most likely it is caused by strong interference signals (e.g. unsteady noise voltage).

Nevertheless, to get reliable values, the instrument offers the possibility of averanging over a longer period.

1.Select a fixed frequency (see "Control loop", Operation)

2.Keep the "START TEST" button pressed until the warning "measured value unstable" disappears. Max. averaging time is approx. 1. min.

Measuring Earthing Impedance with 55 Hz (R*)

For the calculation of short circuit currents in power supply plants, the com- plex 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 • ZE

Measuring process:

The measurement of the earthing impedance (R*) is only possible if it is acti- vated by putting in a personalized user's code (see "Change of Setup Data with Personalized Code"). If this measuring function is activated, in every meas- urement of the four RE positions, the earthing impedance R* is displayed be- fore all other measured values.

Correcting Clip-on Transformer Errors

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 (approx. 1 Ohm - in the range you want to correct) as described in the picture below.

1625 specifications

The Fluke 1625 is a versatile and essential tool in the realm of insulation testing, primarily aimed at electricians, maintenance professionals, and equipment specialists. Throughout its design, Fluke has incorporated a range of features and technologies intended to enhance testing efficiency, accuracy, and user experience, making the 1625 a standout choice for those in need of reliable insulation measurement tools.

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The 1625 also boasts an impressive insulation range of up to 4 GΩ, providing the capability to measure insulation resistance accurately across a spectrum of installations. A notable technology integrated into the unit is the automatic discharge function, which ensures that any stored energy in capacitive components is safely released after testing, enhancing the safety of operations.

Furthermore, the Fluke 1625 includes a patented 'Insulation Diagnostic' feature that assists users in identifying problematic areas in an electrical system. This feature helps professionals determine whether insulation is adequate, helping to prevent potential failures, accidental shorts, and system downtimes.

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In conclusion, the Fluke 1625 is a robust and comprehensive insulation tester that incorporates essential features and advanced technologies. With its versatility, safety mechanisms, and user-friendly design, it stands out as an indispensable tool for electrical professionals committed to ensuring system reliability and safety.