6
GMC-I Messtechnik GmbH
3.4
Measuring the Individual Parameters of an RCD
3.4.1
Touch Voltage Uc
The displayed touch voltage refers to nominal residual current. For
safety reasons, it is multiplied by the following coefficients:
➭
Select the
Uc
function with the
FUNC
key.
➭
The nominal value for residual current can be set with the
I
N
key.
➭
RCD type is selected with the
TYPE
key.
➭
The limit value for touch voltage
Uc
is adjusted with the
xI
N
key.
Figure 3.12: Example: Settings for Touch Voltage Measurement
➭
Connect the instrument to L and PE downstream from the
RCD as shown below. Example:
Figure 3.13: Connection Example
➭
After voltage value U
L-PE
settles in, briefly press the
START
key
to trigger the measurement.
After the measurement has been completed, the results are dis-
played as follows:
Figure 3.14: Results of a Touch Voltage Measurement
RL … fault loop impedance; R
L
= Uc*/
I
N
, where Uc* is actually
measured touch voltage, i.e. without a safety coefficient from the
table at the beginning of this section.
Note
The value for fault loop impedance appears at the display
if residual current
I
N
is set to
30 mA.
➭
Remove the test instrument from the RCD under test.
3.4.2
Time to Trip – TIME
The following table shows time to trip in accordance with the
EN 61008, EN 61009 and IEC 60364-4-41 standards:
* An RCD may not trip at
½
I
N
.
➭
Select the
TIME
function by pressing the
FUNC
key.
➭
The nominal value for residual current can be set with the
I
N
key.
➭
RCD type is selected with the
TYPE
key.
➭
Select a multiplier with the help of the
xI
N
key.
Figure 3.15: Example: Settings for Time to Trip Measurement
➭
Connect the instrument to L and PE downstream from the
RCD as shown in figure 3.13.
➭
After voltage value U
L-PE
settles in, briefly press the
START
key
to trigger the measurement.
After the measurement has been completed, the results are dis-
played as follows:
Uc (touch voltage) … touch voltage value
➭
Remove the test instrument from the RCD under test.
Comment:
Selective RCDs include a delay element which makes it
necessary to wait for a certain amount of time after each mea-
surement until the RCD is returned to its initial state. A 30 second
pause is therefore specified for the measurement of selective
RCDs, the progress of which appears at the display in the form of
a countdown timer which runs from 30 seconds to 1 second:
R C D t y p e
C o n t a c t v o l t a g e i s
p r o p o r t i o n a l t o :
1 , 0 5
I
N
1 , 0 5
2
I
N
1 , 0 5
2
I
N
1 , 0 5
2 x
2
I
N
½
I
N
*
I
N
2
I
N
5
I
N
Comment
Standard
—
300 ms
150 ms
40 ms
max. permissible
tripping current
Selective
—
500 ms
200 ms
150 ms
—
130 ms
60 ms
50 ms
min. permissible
tripping current
Figure 3.16: Results of the
Time to Trip Mea-
surement
Figure 3.17: Results when the
RCD is not
Tripped
