ABB RET 541 Product Manual page 6

Design (cont´d)
6
Transformer Terminal
The indication of a low auxiliary voltage is
available in the transformer terminal configu-
ration and can be connected to any signal out-
put of the RET 54_.
Overtemperature indication
The RET 54_ transformer 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
temperature indication is available in the
transformer terminal configuration and can be
connected to any signal output of the RET
54_.
Analog channels
The transformer terminal measures the analog
signals needed for protection, measuring, etc.
via galvanically separated matching trans-
formers.
RET 54_ transformer terminals have 9 analog
channels. Furthermore, the transformer termi-
nal includes virtual analog channels for calcu-
lating the residual current and residual
voltage from phase currents and voltages.
Both the amplitude and the phase angle are
calculated for the virtual channels.
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.
Analog channels of the transformer terminal
are configured with the CAP 505 Relay Prod-
uct Engineering Tools.
A separate scaling factor can be set for each
analog channel. The factors enable differ-
ences between the ratings of the protected
unit and those of the measuring device (CT
and VT ratio corrections). The setting value
1.00 means that the rated value of the pro-
tected unit is exactly the same as that of the
measuring device.
Digital inputs
The digital inputs of the transformer termi-
nals are voltage controlled and optically iso-
lated with three treshold voltages defined by
the order, see chapter "Ordering". The func-
tion 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 digital 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.

C). Over-
Oscillation suppression
The transformer terminals have two global
parameters for the suppression of digital input
oscillation. The settings of these parameters
determine the oscillation level and hysteresis
for all digital inputs. Event is generated in
case oscillation is detected.
Attributes of a digital input for transformer
terminal configuration
For each digital input, the status of the input
(value), the time tag for the status change
(time) and the validity of the digital input
(invalidity) can be issued by the attributes.
These attributes are available in the trans-
former terminal configuration and can be
used for various purposes.
RTD/analog inputs
The RET 541 and RET 543 transformer ter-
minals equipped with an RTD/analog module
(RTD1) have eight general purpose analog
inputs for DC measurement. The RTD/analog
inputs are galvanically isolated from the
transformer terminal power supply and enclo-
sure. However, the inputs have a common
ground. The general purpose RTD/analog
inputs accept voltage-, current- or resistance-
type signals. For each measuring mode, a
separate parameter is provided for choosing
between the available measurement ranges.
RTD/analog inputs can be applied for e.g.
temperature measurement.
Digital outputs
The outputs of the transformer terminal are
categorized as follows:
• HSPO: High-speed power output, double-
pole contact, preferred for tripping pur-
poses and for circuit breaker and discon-
nector control
• PO: Power output, either single-pole or
double-pole contact, preferred for circuit
breaker and disconnector control
RET 541, RET 543,
RET 545
1MRS755543