Seg WI Series User Manual

3.4 Phase and Ground Current Measuring Inputs
The WIC1 is provided with current measuring inputs for measuring the phase currents and –
for the appropriate variants – one for measuring the earth (ground) current:
• WIC1‑xS: 3 phase current inputs.•
The phase current inputs are designed for the WIC1-compatible CTs, see ╚═▷
“2.6.1.3 Order Form of the WIC1-Compatible Current Transformers”.
◦
WIC1‑xSN: No ground current measurement. The ground current must therefore
◦
be calculated out of the phase currents.
◦ WIC1‑xSG: 1 ground current measuring input, that is designed for a CT with◦
secondary current of 1 A.
• WIC1‑xB: 6 phase current inputs.•
The phase current inputs are designed for special Broad-Range CTs. These feature
two secondary windings. This solves the problem that self-powered protection relays
such as the WIC1, when fed with small primary currents, su󰊞er from a non-linear
transmission characteristic, see also ╚═▷ “3.3.2 Selection of a WIC1-Compatible
Current Transformer”. If the Broad-Range CTs are used the 󰊟rst winding is used for
measurement and for supply, but only in case of primary currents that are not too
small. In case of small primary currents, the 󰊟rst winding is still used for supply, but
the WIC1 automatically switches to the second winding for measurement. This way
the problem with the non-linear characteristic is improved, so that one gets a much
better accuracy for the phase current measurement.
◦ WIC1‑xBN: No ground current measurement. The ground current must therefore◦
be calculated out of the phase currents.
◦
WIC1‑xBG: 1 ground current measuring input, that is designed for a CT with
◦
secondary current of 1 A.
In addition, there are test inputs available for phase currents and ground current, as
dedicated terminals and (internally connected) sockets at the front side of the device. (See
diagrams ╚═▷ Fig. 22, ╚═▷ Fig. 23, ╚═▷ Fig. 24, ╚═▷ Fig. 25.) These test inputs can be used
for secondary tests during commissioning. (See ╚═▷ “7.1.4.2 Wiring Checks”.)
DANGER!
The terminal block for connection to the current transformers is not a shorting block.
Therefore always short-circuit current transformers before loosening the terminals.
Ignoring this can result in dangerous voltages at the open contacts (up to dozens of
kilovolts depending on the CT type).
CAUTION!
Only the special WIC1-compatible CTs are permitted for the phase current inputs! The
connection of common CTs with secondary currents of 1 A or 5 A is not permitted for the
phase current inputs! (An exception is the use of a special adapter CT, see ╚═▷ “3.3.3
Adapter CTs for 1 A”.)
The ground current input – if available – is designed for a CT with secondary current of
1 A.
77WIC1WIC1-1.0-EN-MAN
3 Hardware
3.4 Phase and Ground Current Measuring Inputs

Seg WI Series Specifications

General

Brand	Seg
Model	WI Series
Category	Relays
Language	English