ABB REB500 Mode of installation Distributed busbar protection

There are three versions of installing the numerical busbar protection REB500:

Distributed installation

In this case, the bay units are installed in casings or cubicles in the individual switchgear bays distributed

around the station and are connected to the central processing unit by optical fiber cables (see Figure 5). The

central processing unit is normally located in a central cubicle or in a central relay room.

Centralized installation

The central processing unit and the bay units are mountedin 19 "racks (up to two bay units each rack), according to

the size of the busbar system in one or more cubicles (seeFigure 6). A  centralized installation is the ideal solution for

upgrading existing stations, since very little additional wiring is required and compared with older kinds of busbar

protection, much more functionality can be packed into thesame space.

Combined centralized and distributed installation Basically, the only difference between a distributed and a 

centralized scheme is the mounting location of the bay units and therefore it is possible to mix the two philosophies.

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).

After acquisition, the analog 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, 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 settingsfor 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).