Operating Modes
32
Button /
Menu item
Description
Only adjustable for tests with sine wave or rectangular voltage
This menu item is used to change the frequency of the VLF test voltage
(0.01 Hz to 0.1 Hz). The HD 620 S1 und HD 621 S1 harmonisation
documents recommend the 0.1 Hz frequency for VLF tests.
As the maximum permitted test frequency depends on the determined
cable capacitance and the test voltage being applied (see page 13), it may
be necessary to adjust the test frequency set and about which the user
was informed at the start of the test.
In the Auto setting, the system automatically selects the highest possible
test frequency at the start of the test and starts the voltage conditioning
without further inquiry.
Only adjustable for DC voltage test
This menu item is used to specify the polarity of the DC test voltage.
In this submenu, the following additional parameters can be set:
The manner of entering the voltage. Depending on the voltage
form, the test voltage can be specified as peak value (PEAK), root
mean square value (RMS), absolute value (|U|) or as a multiple of
Uo (x
Uo).
Activates and deactivates the burning function. If the burn function
is activated and a voltage breakdown occurs, the test continues for
the purpose of fault conversion for a maximum one minute.
These settings are stored separately for each of the test modes and are
retained even if the unit is switched off.
The requirements for a meaningful cable test are found in the harmonisation documents
HD 620 S1:1996 and HD 621 S1:1996 and often in company-internal testing guidelines
as well.
The following table provides a selection of proven test parameters for various
applications:
Application Test voltage Test duration in
minutes
VLF test (new cables) 3 Uo 15 to 60
VLF test (on aged cables) 1.7 to 3 Uo 60
DC test (on PILC cables) 4 to 8 Uo 15 to 30
test voltage and test
time
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