System Design - ABB RELION REB500 Product Manual

Distributed busbar protection REB500
Version 8.3 IEC

4. System design

Bay unit (500BU04)
The bay unit is the interface between the protection and
the primary system process comprised of the main CTs,
isolators and circuit-breaker and performs the
associated data acquisition, pre-processing, control
functions and bay level protection functions. It also
provides the electrical insulation between the primary
system and the internal electronics of the protection.
The bay unit contains four input CTs for measuring
phase and neutral currents with terminals for 1 A and 5
A. Additional interposing CTs are not required, because
any differences between the CT ratios are compensated
by appropriately configuring the software parameter of
the respective bay units.
The bay unit optionally contains five input voltage
transformers for the measurement of the three-phase
voltages and two busbar voltages to allow the recording
of voltage disturbances. (see
After acquisition, the analogue current and voltage
signals are converted to numerical signals which are
preprocessed and filtered. Zero-sequence voltage and
zerocurrent signals are also calculated internally. The
process data are transferred at regular intervals from
the bay units to the central processing unit via the
REB500 process bus.
Every bay unit has a minimum of 21 binary inputs and 19
binary outputs. The binary I/O module can be used to
detect and process the positions of isolators and
couplers, blocking signals, starting signals, external
resetting signals and so on.
The binary input channels operate according to a
patented pulse modulation principle in a nominal range
of 24 to 250 V DC. The PC-based HMI program provides
settings for the threshold voltage of the binary inputs.
Out of 19 binary outputs, 6 are equipped with power
output relays and 13 are signal output relays (see
contact data in Section
Additional 12 inputs and 6 precision outputs are
available as an option. The precision outputs are based
on MOSFET technology and offer an improved trip-time
performance.
A software logic enables the input and output channels
to be assigned to the various functions. A time stamp is
attached to all the data such as currents, voltages,
binary inputs, events and diagnostic information
acquired by a bay unit.
ABB
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Section 10).
10).
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Where more analogue and binary inputs are needed,
several bay units can be combined to form a feeder/bus
coupler bay (for example, a bus coupler bay with CTs on
both sides of the bus-tie breaker requires two bay
units).
The bay unit is provided with local intelligence and
performs local protection (for example, breaker failure,
end fault, breaker pole discrepancy) as well as the event
and disturbance recording.
In the event that the central unit is out of operation or
the optical fiber communication is disrupted an alarm is
generated. The bay unit will continue to operate and all
local protection as well as the recorders (event and
disturbance) will remain fully functional (stand-alone
operation).
The hardware structure is based on a closed, monolithic
casing and presented in two mounting solutions:
• Without LHMI: ideal solution if convenient access to all
information via the central unit or by an existing
substation automation system is sufficient.
• With LHMI and 15 programmable LEDs
solution for distributed and kiosk mounting (AIS),
since all information is available in the bay. For this
option it is possible to have the LHMI either built in or
connected via a flexible cable to a fixed mounting
position.
IEC18000577 V2 EN-US
Figure 7. Bay Unit
Additional plug-and-play functionality
Bay units can be added to an existing REB500 system in
a simple way. Due to the modular and flexible
architecture of the software, integration of new units is
easily achieved.
1MRK 505 402-BEN B
(Figure 7): ideal
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