für ANNA angelegt 2004-06-25 für ANNA aktualisiert 2004-06-26

Description of a measuring method

Risol

Isolation Resistance



The Procedure

Test of isolation distances and components with constant DC voltage.

Test voltage and the leakage current are measured and recorded.
The resistance is calculated as U/J by PC.

Measuring Ranges

Voltage according to layout of the device up to 2kV or 3kV.
Switch between two measuring ranges:
Range NV: 800V resolution 0.2V
Range HV: 2kV/3kV resolution 1V

Strom je nach Ausstattung des Geräts bis 2mA oder 10mA.

Measuring Parameters

Tms: measuring time - duration from start to reading measuring data.
Ums: Test Voltage
Imax: current limitation in case of failure.

Properties

With manual operation generally the leakage current is displayed.

At operation with a PC measured test voltage, leakage current and the resistance computed from it are available and can be used independently of each other as criteria for the evaluation with the help of tolerance borders.

Tips and Tricks

Generally the test runs quick (Tms = 0.3. 0.7s).

Gas discharge arresters should show an isolation resistance greater than 10 Gigaohm.

Varistoren show a leakage current which can strongly depend on the voltage and the measuring duration.
As long as test voltage is applied, the leakage current drops considerably. With repetition of the measurement in the identical polarity the leakage current remains low and drops further during the measurement, in reverse polarity the measurement starts again with a high leakage current.

For the test of Varistors, having possibly minimum damages - e.g., by current pulses - , an isolation test is recommended with a D.C. test voltage as high as the expected peak voltage in normal operation - e.g., 350 V of test voltage for 230Vrms of A.C.


Overview about the measuring methods.



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