Feeder Terminal
REF 541, REF 543, REF 545.
1MRS750443-MBG
6
Other functions
Low auxiliary voltage indication
The REF 54_ feeder terminal is provided
with a low auxiliary voltage indication fea-
ture. The power supply module issues an
internal alarm signal when a drop in the
power supply voltage is detected (ACFail,
active low). The alarm signal is activated if
the power supply voltage falls about 10%
below the lowest rated DC input voltage of
the power supply module.
The indication of a low auxiliary voltage is
available in the feeder terminal configuration
and can be connected to any signal output of
the REF 54_.
Overtemperature indication
The REF 54_ feeder terminal includes an
internal temperature supervision function.
The power supply module issues an internal
alarm signal when overtemperature has been
detected inside the terminal enclosure. The
alarm signal will be activated once the tem-
perature inside the terminal enclosure
increases to +78
C (+75
...+83
C). Over-
temperature indication is available in the
feeder terminal configuration and can be con-
nected to any signal output of the terminal.
Analog channels
The feeder terminal measures the analogue
signals needed for protection, measuring, etc.
via sensors or galvanically separated match-
ing transformers.
Depending on whether sensors are included
or not, REF 54_ feeder terminals have 9
(without sensors) or 10 (with sensors) ana-
logue channels. The number of channels used
depends on the feeder terminal configuration
and the kind of matching transformers or sen-
sor inputs used. Furthermore, the feeder ter-
minal includes virtual analogue channels for
calculating the phase-to-phase voltages, neu-
tral current and residual voltage from phase
currents and voltages.
In addition to 9 conventional matching trans-
formers, sensors developed by ABB can be
used parallel in REF 54_ feeder terminals.
The feeder terminal has 9 sensor inputs. A
current sensor (Rogowski coil) or a voltage
divider can be connected to each sensor input.
Please, see the connection diagram for
details. When ordering, please note the type
of analogue inputs.
Each analog channel is separately configured
with the
Relay Configuration Tool
. Both the
measuring unit for each analog channel and
the type of signal to be measured are to be
configured.
A separate scaling factor can be set for each
analogue channel. The factors enable differ-
ences between the ratings of the protected
unit and those of the measuring device (CTs,
VTs etc.). The setting value 1.00 means that
the rated value of the protected unit is exactly
the same as that of the measuring device.
Calculated analogue channels
The REF 54_ feeder terminal includes virtual
channels to obtain phase-to-phase voltages,
neutral current and residual voltage when
sensors are used. Sensors are connected to the
feeder terminal via coaxial cables and there-
fore a residual connection of phase currents
or an open-delta connection of phase voltages
cannot be made. Both the amplitude and the
phase angle are calculated for the virtual
channels.
Though primarily meant to be used with sen-
sors, the calculated analogue channels can
also be used with conventional current and
voltage transformers.
Note! When sensitive earth-fault protection is
needed, core balance transformers are not
recommended to be replaced with the numer-
ically derived sum of phase currents. Nor-
mally, an earth-fault setting below 10% of the
rated value requires the use of a core balance
transformer.
Digital inputs
The digital inputs of the feeder terminals are
voltage-controlled and optically isolated. The
function of a digital input can be inverted.
The programmable filter time removes
debounces and short disturbances on a digital
input. The filter time can be set for each digi-
tal input separately.
Some specific digital inputs can be pro-
grammed to operate either as digital inputs, as
pulse counters or as used for time synchroni-
zation. When a digital input operates as a
pulse counter, pulse counting frequency can
be up to100 Hz.
Oscillation suppression
The feeder terminals have two global parame-
ters for the suppression of digital input oscil-
lation. The settings of these parameters