METREL MI 3399, Инструкция с упражнениями

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Electrical Installation Safety Trainer AD 1 - MI 3399
73
The result of both test is shown as passed. The correct result of the measurement
should be fail since the PE has an error simulated. Because Z
S RCD
is not the proper
method for measuring fault loop on a RCD protected system the true fault is not
discovered by the device and the device returns a false positive. A better function to
measure the resistance in this case would be the R
PE
function. If a fuse with a higher
allowed current were to be used the result would also be shown as failed in this case.
If we simulate an error in the line (L) conductor instead of the PE conductor, the test
should fail since we introduce an additional 10
Ω to the wiring on the line conductor.
This is done by enabling switches S12 (3-phase), S13 (1-phase) or S14 (1-phase) in
the Application Trainer.
Figure 2-21: Simulated errors on the line conductor
In a 1-phase TN system the maximum allowed impedance result for a 6A gG type fuse
with 400ms trip-out time is
4,6
Ω
, whereas in a 3-phase TN system the maximum
allowed impedance result for a 6A B type fuse with 200ms trip-out time is 7,3
Ω
7
.
The result is that the test fails since the measured impedance value are higher than
the maximum allowed (
4,6
Ω
and 7,3
Ω
) for both types of fuses.
7
See chapter 1.4 Ensurance of Safety for more details on fuse and RCD trip-out times and impedances.
E
xer
ci
ses
S
w
itch
Function Site of error ON OFF
S12 Z LINE
TN/TT F1/2
L3/N outlet (3-ph.)
> 10
Ω
< 2
Ω
S13 Z LINE
TN/TT F2/2
L1/N outlet
> 10
Ω
< 2
Ω
S14 Z LINE
TN/TT F1/3
L3/N outlet
> 10
Ω
< 2
Ω
L
in
e
Im
p
e
d
a
n
c
e