INSTALLATION
53
NA011 - Manual - 05 - 2022
Earth
A protective ground connection is required, which must be connected to the suitable screw with a
separate lead of at least 2.5 mm
2
; the connection from A21 or a22 terminal and the ground srew is
also required.
[1]
CT amperometric inputs
The amperometric input circuits are assembled inside the fixed module, so no short circuit on the
secondary CTs must be provided when the removable module is pulled out
In the event of case replacement, some camps must be provided externally to shorting the second-
ary CTs circuits to avoid secondary open circuit of CTs that may endanger equipment or people.
When making the current connections, attention must be paid to not exceeding the performance
of the line current transformers. To be exact, the total load, constituted by the protective relay, any
other protective relays or measuring instruments and the resistance of the connections, must not ex-
ceed the line CT performance. In particular, consumption of the relay input circuit must not exceed
0.2 VA while the load (expressed in VA) constituted by the conductors is given by:
0.018 × L ×
I
n
2
/ S
where:
L the overall length, expressed in m, of the two conductors in relation to each phase;
I
n
nominal current of the line CT expressed in A;
S cross sectional area of the current conductors expressed in mm
2
.
It is recommended that cabling of a suitable thickness be used in order to limit wear of the CT sec-
ondary circuits.
LPCT amperometric inputs
The amperometric input are designed for Low Power Current Transformer with 100 A - 22.5 mv ratio.
Connections to NA011 device must be carried out by means RJ45 plugs, forming a part of the Trans-
former.
[2]
Note 1 The A21 and A22 terminal are link together inside the relay
Nota 2 For technical data please call Thytronic.
In case of disconnection CT wiring to the case, pay attention must to do not open live circuits.
CAUTION
rear.ai
Earthing
Ground screw
