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EXAMPLE DIP-SWITCH SETTINGS
In this example;
1. The sip-switch settings of the relay belonging to a 3 CT feeder.
2. The current transformer ratio is 300 A / 5 A.
3. The phase overcurrent protection range will be (0.1 - 40) I
n
.
4. There are no residual current transformers; instead, the secondary circuits of the phase CTs are
bridged and earthed over the earth protection current input of the relay, thus, the nominal
secondary current of earth protection is the same as phases and it is I
en
= 5 A.
5. The earth fault protection range is required as (0.1 - 40) I
en
.
The settings to be done on the dip-switches are as follows:
As the current transformer ratio is 300 A / 5 A, the secondary nominal
current for phases is 5 A. According to that, the T, S and R dip-
switches (no. 3, 4, 5) are made to the upper position, so set as “ON”.
The secondary nominal current for earth is 5 A and range is required
as (0.1 - 40) I
en
. According to that, as explained on the page before,
the E1 and E2 dip-switches (no. 1 and 2) are made to the upper
position, so set as “ON”.
Make the current transformer settings at the relay menu to complete
the settings.
WARNINGS
DEMA CPM 310 G units are set to “ON – ON –ON – ON – ON” dip-switch settings by default. The
default setting presumes that:
o the nominal current for phases and earth is 5 A
o the protection range for phases and earth is (0.1 - 40) I
n
To ensure correct operation of the relay, make sure to check the dip-switch settings physically and
current transformer settings on the relay menu before commissioning!
If the dip-switch settings for the earth protection is changed, the relay resets the protection
settings of all earth protection functions (I
e
>, I
e
>>, I
e
>>>) to default. Make sure to set these
functions once the dip-switch settings are completed. □
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