ABB CB801 3BSE042245R1 PROFIBUS DP panel communication unit
Bay unit (500BU03)
The bay unit (see Fig. 4) is the interface
between the protection and the primary sys tem process comprising the main CTs, isola tors and circuit-breaker and performs the
associated data acquisition, pre-processing,
control functions and bay level protection
functions. It also provides the electrical insula tion between the primary system and the
internal electronics of the protection.
The input transformer module contains four
input CTs for measuring phase and neutral
currents with terminals for 1 A and 5 A. Addi tional interposing CTs are not required,
because any differences between the CT
ratios are compensated by appropriately con figuring the software of the respective bay units.
Optional input transformer module also con tains five input voltage transformers for the
measurement of the three-phase voltages and
two busbar voltages and recording of voltage
disturbances or 6 current transformers for
transformer differential protection. (see Fig. 12).
In the analog input and processing module,
the analog current and voltage signals are
converted to numerical signals at a sampling
rate of 48 samples per period and then
numerically preprocessed and filtered accord ingly. Zero-sequence voltage and zero-current
signals are also calculated internally. The Pro cess data are transferred at regular intervals
from the bay units to the central processing
unit via the process bus.
Every bay unit has 20 binary inputs and 16
relay outputs. The binary I/O module detects
and processes the positions of isolators and
couplers, blocking signals, starting signals,
external resetting signals, etc. The binary
input channels operate according to a pat ented pulse modulation principle in a nominal
range of 48 to 250 V DC. The PC-based HMI
program provides settings for the threshold
voltage of the binary inputs. All the binary out put channels are equipped with fast operating
relays and can be used for either signaling or
tripping purposes (see contact data in Table 8).
A software logic enables the input and output
channels to be assigned to the various func tions. A time stamp is attached to all the data
such as currents, voltages, binary inputs,
events and diagnostic information acquired by
a bay unit.
Where more binary and analog inputs are
needed, several bay units can be combined to
form a feeder/bus coupler bay (e.g. a bus cou pler 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 (e.g. breaker
failure, end fault, breaker pole discrepancy),
bay protection (Main 2 or back-up bay protec tions) 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 and bay 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 local HMI: ideal solution if convenient access to all information via the central unit or by an existing substation
automation system is sufficient.
• With local HMI and 20 programmable LEDs
(Fig. 5): ideal solution for distributed and
kiosk mounting (AIS), since all information
is available in the bay.
For the latter option it is possible to have the
HMI either built in or connected via a flexible
cable to a fixed mounting position (see
Fig. 28).
In the event of a failure, a bay unit can be easily replaced. The replacement of a bay unit
can be handled in a simple way. During system start-up the new bay unit requests its
address, this can be entered directly via its
local HMI. The necessary setting values and
configuration data are then downloaded automatically.
Additional plug-and-play functionality
Bay units can be added to an existing
REB500 system in a simple way.
Fig. 5 Bay unit
Central unit (500CU03)
The hardware structure is based on standard
racks and only a few different module types
for the central unit (see Fig. 4).
The modules actually installed in a particular
protection scheme depend on the size, complexity and functionality of the busbar system.
A parallel bus on a front-plate motherboard
establishes the interconnections between the
modules in a rack. The modules are inserted
from the rear.
The central unit is the system manager, i.e. it
configures the system, contains the busbar
replica, assigns bays within the system, manages the sets of operating parameters, acts as
process bus controller, assures synchronization of the system and controls communication with the station control system.
The variables for the busbar protection function are derived dynamically from the process
data provided by the bay units.
The process data are transferred to the central processor via a star coupler module. Up to
10 bay units can be connected to the first central processor and 10 to the others. Central
processors and star coupler modules are
added for protection systems that include
more than 10 bay units. In the case of more
than 30 bay units, additional casings are
required for accommodating the additional
central processors and star coupler modules
required.
All modules of the central unit have a plugand-play functionality in order to minimize
module configuration.
One or two binary I/O modules can be connected to a central processing unit.
The central unit comprises a local HMI with 20
programmable LEDs (Fig. 6), a TCP/IP port
for very fast HMI500 connection within the
local area network.