Multifunction Protection and Switchgear Control unit REF542plus
Manual: Motor Protection with ATEX-Certification
Figure 20: Example of mounting of the Central Unit in the LV compartment and the HMI
on the door
7.2.3 Wiring the REF542plus
Follow the bay documentation supplied for the wiring.
In conclusion, the checks described in the following paragraphs can be done to en-
sure that the wiring is correctly installed.
7.2.3.1 Checking the current transformer circuits
To check that the current transformer and the current transformer circuits are wired
correctly, run the following checks:
Polarity check
The polarity check (as close as possible to the REF542plus) is used to check the cur-
rent circuit and also the installation position and the polarity of the transducer. The po-
larity of the transducers to one another can also be checked with load current.
Current feed with heavy current source (primary test instrument).
The current feed provides information on the transducer transformation and the cor-
rect wiring to the REF542plus. The power supply should be per conductor and run
from conductor to conductor in each case. All line currents and the residual current
should be checked here.
The transducer transformation can also be checked with load current.
Recording the magnetizing characteristic
Recording the magnetizing characteristic ensures that the REF542plus is connected
to a protective core and not to a measuring core.
Checking the transducer circuit ground
Every independent current circuit may be grounded at only one point to prevent bal-
ancing currents resulting from potential differences.
Check the grounding of the cable current transformer (when used)
If the neutral current is measured by a cable current transformer, the cable shielding
should first be returned through the cable current transformer before connecting it to
the ground.
1VTA100114-Rev. 04 en PTMV, 19.01.05 Motorprotection 45 / 66
Valid from Version V4D02
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