S-50 DC
● S-80 DC ● S-110 DC ● S-120 DC – USER MANUAL
14
Selector switch
– current measuring range
Switches between the current measuring ranges
Ground terminal
Connection of the operating unit to ground potential (protective ground)
Display selection switch
– voltmeter
Switches between meter- and graph-display, changes time base
Display selection switch
– ammeter
Switches between meter- and graph-display, changes time base
4.2
Operating procedure
4.2.1
Setting the operating parameters
When measuring the insulation resistance of plant or plant components with primarily resistive content,
the "Load" selector switch
has to be set to "R". This is necessary if an exact reading of the meas-
ured value is to be obtained. If cables, plant or plant components with primarily capacitive content are
tested, the selector switch must be set to "C".
Before starting measurement, select the largest current measuring range (10 mA).
4.2.2
Performing measurements
When the mains switch is turned on, the white pilot lamp
lights up. If the equipment is grounded
properly, the yellow pilot lamp
also lights up. If this does not happen, the operating unit still has to
be grounded with cable 1 (ground cable for operating unit to station ground).
Pilot lamp
signals proper connection of the station and protective grounds independently of the
high voltage being connected. The equipment will only work when both lamps are lit.
The green "HV On"
button switches the high voltage on if the voltage regulating transformer
in
zero position at left stop (second switching operation, interlock, forced zero position).
The red illuminated "HV Off"
button lights up at the same time, indicating that the high voltage is
switched on. Once the prescribed test voltage has been reached, the leakage current of the test object
can be measured by operating the selector switch for the current measuring range (0.1 mA, 1 mA,
10 mA).
The test voltage can now be set by slowly turning the adjuster clockwise. While doing this, remember
to follow the increase in voltage and current on the instruments. Once the prescribed test voltage has
been reached, the leakage current of the test object can be measured by operating the selector switch
for the current measuring range (0.1 mA, 1 mA, 10 mA).
The following guide values can be quoted for paper-insulated mass-impregnated cables.
Table 4.2 Guide values for leakage currents
Nominal cable
voltage [kV]
Test voltage [kV]
Leakage current per wire [µA/km]
permitted
min. achievable
6
35
500
23
10
50
700
30
20
80
700
80
30
110
700
100
