Installation and connection
21
RCM420_D00057_03_M_ XXEN/03.2021
Connection of an additional cascaded measuring current
transformer
If the residual current range of 10 A is not sufficient, an additional measuring
current transformer can be cascaded. Connect the measuring current trans-
former as illustrated in the drawing below.
Example:
An additionally cascaded transformer on the load side has a transmission
ratio of X
1
= 100 (500 A / 5 A). That means, when the lowest value of 10 mA is
set at the RCM420, a current of 1 A can only just be detected on the primary
side of the transformer on the load side. In order to reduce the value that can
be detected to 100 mA, 10 turns of the supply cable has to be routed through
the transformer on the RCM side.
Hence, the correction factor to be set is
n
RCM
= X
1
:X
2
= 100:10 = 10.
The correction factor can be set via the SEt/n menu.
The correction factor is factory set to 1 and relates to normal operation with
one Bender measuring current transformer only (X = 600:1).
Bender
CTAC…, WR…, WS…
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