System Design - ABB Relion REB500 Product Manual

Distributed busbar protection REB500
Product version: 8.2
Figure 6. Centralized installation
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 Chapter 10).
10
After acquisition, the analog current and voltage signals
are converted to numerical signals which are pre-
processed and filtered. Zero-sequence voltage and zero-
current 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, etc.
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 the 19 binary outputs, 6 are equipped with power
output relays and 13 are signal output relays (see contact
data in Chapter 10).
Additional 12 inputs and 6 precision outputs are available
as an option. The precision outputs are based on
1MRK 505 352-BEN
Issued: 2016-03-01
Revision: -
ABB