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FUNCTION CHARACTERISTICS
31 NA011 - Manual - 05 - 2022
4.4 PROTECTIVE ELEMENTS
Traditional CT inputs
• Relay phase nominal current I
n
This nominal value must be set by means dip-switch to 1 A or 5 A, same as the secondary CTs
nominal current.
Dip-switches are located on the CPU board; the exhaustive treatment of Dip setup is described in
the “6.4 SETTING NOMINAL CURRENTS I
n
AND I
En
” paragraph.
• Relay residual nominal current I
En
• For NA011#xxx2 versions, the rated value must be set by means dip-switch to 1 A or 5 A, same as
the secondary nominal current of the residual CT.
Dip-switch is located on the CPU board; the exhaustive treatment of Dip setup is described in the
“6.4 SETTING NOMINAL CURRENTS I
n
AND I
En
” paragraph.
• For NA011#xxx0 versions, the rated value is automatically set to the phase nominal current.
[1]
Low Power CT inputs
• Relay phase nominal current I
n
This nominal value must be set by means dip-switch to 50 A to 1250 A, same as the primary nominal
current of the protected plant. All settings of the current thresholds are referred to the rated cur-
rent of the relay I
n
, that corresponds to the primary value automatically set as just described.
Dip-switches are located on the rear board; the exhaustive treatment of Dip setup is described in
the “6.5 NOMINAL CURRENT In SETTING FOR LPCT” paragraph.
• Relay residual nominal current I
En
• For NA011#xxx3 versions, the rated value must be set by means dip-switch to 1 A or 5 A, same as
the secondary nominal current of the residual CT.
Dip-switch is located on board of the CPU board; the exhaustive treatment of Dip setup is de-
scribed in the “6.4 and 6.5 SETTING NOMINAL CURRENTS I
n
AND I
En
” paragraph.
• For NA011#xxx1 versions, the rated value is automatically set to the phase nominal current.
[1]
Settings
Inside the Set \ Base menu the following parameters can be set:
• Primary rated values (phase and residual), employed for measures relative to primary values.
• Measurements reading mode (
Reading Direct or Relative
).
• Phase CT primary current I
np
This parameter affects the measure of the phase currents when the primary measurement reading
mode is selected (
Reading Direct
). It must be programmed to the same value of the phase CT
primary nominal current Traditional CTs) or to the value set for the LPCT inputs.
Example
The phase CT primary current I
np
must be set as: I
np
= 500 A
• Residual CT primary current I
Enp
This parameter affects the measure of the residual current when the primary measurement read-
ing mode is selected with traditional CTs inputs. It must be programmed to the same value of the
residual CTs primary nominal current.
Example 1
The residual CT primary current I
Enp
must be set as: I
Enp
= 100 A
Note 1 The residual current is calculated by the vector sum of the three phase currents.
Es-In.ai
K
CT
= 500A/5A=100
52
I
n
NA011
I
L1...
I
L3
LPCT
s CURRENT INPUTS
L1
L2
L3
In = 500 A
In = 500 A
In = 500 A
LPCT Setting
800 A
400 A
200 A
100 A
50 A
In=50...1250A
1A/5A
Es1-IEn.ai
1x
K
TA
= 100 A /1 A
52
I
En
= 1 A
NA011