Month: June 2025

Resetting the trip commands/signals

The following resetting modes can be selected for each binary output (tripping or signal outputs):

· Latches until manually reset

· Resets automatically after a delay

Inspection/maintenance

A binary input can be assigned that excludes a bay unit from evaluation by the protection system. 

It is used while performing maintenance or inspection activities on the primary equipment respectively.

Redundant power supplies (Optional)

The central unit may be ordered with a redundant power supply.

Time synchronization

The absolute time accuracy with respect to an external time reference depends on the method of synchronization

7. Requirements

Optical fiber cables

A distributed busbar protection layout requires optical fiber cables and connectors with the following characteristics:

· 2 optical fiber cores per bay unit

· glass fibers with gradient index

· diameter of core 62.5/50 µm, sheath 125 µm

· maximum permissible attenuation ≤ 8 dB/6dB

· LC connector (for 62.5/50 µm optical fibers)

· rodent protected and longitudinally waterproof if in cable ducts

Please observe the permissible bending radius when laying the cables.

Additional features

Self-supervision

All the system functions are continuously monitored to ensure the maximum reliability and availability of the

protection. In the event of a failure, incorrect response or inconsistency, the corresponding action is taken to

establish a safe status, an alarm is given and an event is registered for subsequent diagnostic analysis.

Important items of hardware (e.g. auxiliary supplies, A/D converters and main and program memories) are

subjected to various tests when the system is switched on and also during operation. 

A watchdog continuously monitors the integrity of the software functions and the

exchange of data via the REB500 process bus is also continuously supervised.

Extension of the system

The system functions are determined by software,configured using the software configuration tool.

The system can be completely engineered in advance to correspond to the final state of the station. 

The software modules for new bays or features can be activated using

the HMI500 when the primary plant is installed or the features are needed.

Additional system functions, e.g. breaker failure or end fault protection can be easily activated at any time without extra hardware.

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).

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.

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.

In the event of a failure, a bay unit can be easily replaced.

During system startup the new bay unit requests its address, this can be entered directly via its LHMI.

The necessary setting values and configuration data are then downloaded automatically Central unit (500CU04)

The hardware structure is based on a closed, monolithic casing.

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 REB500 process bus controller,

assures synchronization of the system and communicates with the station control and monitoring system.

The variables for the busbar protection function are derived dynamically from the process data provided by the bay units.

The process data is transferred to the central processor via the REB500 process bus interface.

The central unit is able to handle data from up to 60 bay units and evaluate up to 32 bus zones.

In addition to processing the protection zone data, the central unit provides a disturbance recorder for all 32 bus

zones, recording the main data of the busbar protection to facilitate quick fault analysis.

The central unit offers 9 binary inputs and 19 binary outputs for central commands and signals (e.g. external

bus zone trip, trip-reset etc.). Additional 9 binary inputs and 9 binary outputs are optional available.

The central unit comprises a local HMI with 15 programmable LEDs (Figure 8) including a front Ethernet

port for HMI connection within the local area network.

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.

Where more analog and binary inputs are needed, several bay units can be combined to form a feeder/bus coupler

bay (e.g. 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 (e.g. 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 (Figure 7): ideal 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.

Modular and flexible architecture

· Multiple modes of installation

– Centralized layout:

Installation of bay units and central unit in one or several cubicles

– Distributed layout:

Bay units distributed with short connections to CTs,isolators, circuit breakers, etc.

· Interference-proof connections between bay units and central unit by fiber-optic cables (max. 2000m)

· Replacement of existing busbar protection schemes without restrictions e.g. in case of substation extensions

· Easily extensible

· Only one hardware version for

– Settable 1A and 5A rated current inputs

– Nominal frequencies of 50Hz and 60Hz

· Minimum number of spare parts needed due to standardization and low number of varying units

Seamless substation automation integration

· User-friendly, PC-based interface (HMI)

· Operator integration into PCM600 for readout of configuration, events and disturbance records.

· Communication with substation monitoring and control system

– via IEC 61850-8-1 Edition 1 or Edition 2

– via IEC 60870-5-103

· Local HMI with comprehensive system information on every unit

· Fully numerical signal processing

· Comprehensive self-supervision

· Integrated event recording

· Integrated disturbance recording for power system currents and voltages

· Optional redundant power supply for central units

Cyber security

· Secure communication

· User Access Management

· User Activity Logging

· Centralized account management

· Verified robustness

Additional options

· Breaker failure protection

· Check-zone protection

· End-fault protection

· Definite time overcurrent protection

· Breaker pole discrepancy protection

· Current and voltage release criteria for busbar protection

· Separate I0 measurement for impedance-grounded networks

· Advanced user configurable logic capability

REB500 bay protection (optional)

The system provides an option to extend the functional scope of REB500 by a set of predefined bay protection

functions used as main 2 or back-up line protection.

Version ‘Line variant L-V2’ includes distance, directional/non directional overcurrent and directional earthfault protection functions (see Table 2).

As regards the level of voltages and frequencies busbar and station protection have the same application area.

For details on application and technical data refer to the REB500 Application Manual for bay protection functions.

Main features

Low-impedance busbar protection

· High functional reliability due to two independent measurement criteria:

– stabilized differential current algorithm

– directional current comparison algorithm

· Short tripping times independent of the plant’s size or busbar configuration

· Phase Segregated measurement

· Stub and T-zone protection

· Reduced CT performance requirements

– High through-fault stability even in case of CT saturation

– No switching of CT circuits

Application

REB500

The numerical busbar protection REB500 is designed for the high-speed (sub-cycle), selective protection of MV, HV

and EHV busbar installations at a nominal frequency of 50, 60 Hz The modular system structure is enabling the protection to

be easily configured to suit the layout of the primary system.

The flexibility of the system enables all configurations of busbars from single to quadruple, with transfer buses or

ring busbars and 1½ breaker schemes to be protected.

In 1½ breaker schemes the busbars and entire diameters, including Stub/T-Zone can be protected. 

An integrated tripping scheme allows saving external logics as well as wiring.

The system is scalable for up to 60 feeders (bay units) and a total of 32 busbar zones.

The numerical busbar protection REB500 detects all phase and earth faults in solidly grounded and resistivegrounded power systems and phase faults in ungrounded

systems and systems with Petersen coils.

The main CTs supplying the currents to the busbar protection have to fulfill only modest performance

requirements (see page 17). The protection operates discriminatively for all faults inside the zone of protection

and remains reliably stable for all faults outside the zone of protection.

The differential function offers a high sensitivity for low-level internal faults.

RET 670’s unique and innovative sensitive differential protection feature, based on well-known theory of symmetrical components provide best possible coverage for

winding internal turn-to-turn faults.

A low impedance restricted earth-fault protection function is available as complimentary sensitive and fast main protection against winding earth

faults. This function includes a directional zero-sequence current criterion for additional security.

Alternatively a high impedance differential function is available.

It can be used as restricted earth

fault or, as three functions are included, also as differential protection on autotransformers,

as differential protection for a tertiary connected reactor, as T-differential protection for the transformer feeder in a mesh-corner or ring arrangement,

as tertiary bus protection etc.

Tripping from Buchholz and temperature devices can be done through the IED where pulsing, lock-out etc. is performed.

The binary inputs are heavily stabilized against disturbance to prevent incorrect operations at e.g. dc system capacitive discharges.

Distance protection functionality for phase to phase and/or phase to earth faults is available as back-up protection

for faults within the transformer and in the connected power system.

Versatile phase, earth, positive, negative and zero sequence overcurrent functions,

which can optionally be made directional and/or voltage controlled,

provide further alternative backup protection.

Thermal overload, volts per hertz, over/under voltage and over/under frequency protection functions are also available.

Built-in disturbance and event recorder provides valuable data to the user about status and operation for post-fault disturbance analysis.

Breaker failure protection for each transformer breaker allow high speed back-up tripping of surrounding breakers.

The IED can also be provided with a full control and interlocking functionality including Synchrocheck function to allow integration of the main or

a local back-up control.

The advanced logic capability, where user logic is prepared with a graphical tool, allows special applications such as

automatic opening of disconnectors in multi-breaker arrangements, closing of breaker rings, load transfer logic etc.

The graphical configuration tool ensures simple and fast testing and commissioning.

Serial data communication is via optical connections to ensure immunity against disturbances.

The wide application flexibility makes this product an excellent choice for both new installations and the refurbishment of existing installations.