ABB Distributed busbar protection REB500

ABB Distributed busbar protection REB500

Main features

• Low-impedance busbar protection

• Stub and T-zone protection

• High functional reliability due to two independent

measurement criteria:

- stabilized differential current algorithm

- directional current comparison algorithm

• Phase-by-phase measurement

• Reduced CT performance requirements

• High through-fault stability even in case of

CT saturation

• Full solid-state busbar replica

• No switching of CT circuits

• Only one hardware version for

- 1 and 5 A rated currents

- all auxiliary supply voltages between 

48 V DC an

Bay unit (500BU03)

The bay unit (see Fig. 4) is the interface

between the protection and the primary system

process comprising 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 input transformer module 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 of the respective bay

units.

Optional input transformer module also contains

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 accordingly.

Zero-sequence voltage and zero-current

signals are also calculated internally. The Process

d 250 V DC

- nominal frequencies of 50, 60 and 

16.7 Hz

• Short tripping times independent of the

plant’s size or configuration

• Centralized layout: Installation of hardware

in one or several cubicles

• Distributed layout: Bay units distributed

and, in the case of location close to the

feeders, with short connections to CTs, isolators,

circuit breakers, etc.

• Connections between bay units and central

unit by fiber-optic cables

- maximum permissible length 1200 m

- for distributed and centralized layout

• fiber-optic connections mean interferenceproof

data transfer even close to HV power

cables

• Replacement of existing busbar protection

schemes can be accomplished without restrictions

(centralized layout) in the case of

substation extensions e.g. by a mixture of

centralized and distributed layout

• Easily extensible

• User-friendly, PC-based human machine

interface (HMI)

• Fully numerical signal processing

• Comprehensive self-supervision

• Binary logic and timer in the bay unit

• Integrated event recording

• Integrated disturbance recording for power

system currents

• A minimum of spare parts needed due to

standardization and a low number of varying

units

• Communication facilities for substation

monitoring and control systems via 

IEC 61850-8-1, IEC 60870-5-103 and LON

• IEC 62439 standard redundant station bus

communication

• IEC 61850-9-2 LE process bus communication

• Cyber security to support

- User Access Management

- User Activity Logging

Options

• Breaker failure protection (also separately

operable without busbar protection)

• End fault protection

• Definite time overcurrent protection

• Breaker pole discrepancy

• Current and voltage release criteria

• Disturbance recording for power system

voltages

• Separate I0 measurement for impedancegrounded

networks

• Communication with substation monitoring

and control system (IEC 61850-8-1 /

IEC 60870-5-103 / LON)

• Internal user-friendly human machine interface

with display

• Redundant power supply for central units

and/or bay units

REB500

The numerical busbar protection REB500 is

designed for the high-speed, selective protection

of MV, HV and EHV busbar installations

at a nominal frequency of 50, 60 and 16.7 Hz.

The structure of both hardware and software

is modular 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 busbars to

quadruple busbars with transfer buses, ring

busbars and 1½ breaker schemes to be protected.

In 1½ breaker schemes the busbars and the

entire diameters, including Stub/T-Zone can

be protected. An integrated tripping scheme

allows to save external logics as well as wiring.

The capacity is sufficient 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 resistive-grounded 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 fulfil only modest

performance requirements (see page 18). The

protection operates discriminatively for all

faults inside the zone of protection and

remains reliably stable for all faults outside the

zone of protection.

REB500sys

The REB500sys is foreseen in MV, HV and

EHV substations with nominal frequencies of

16.7, 50 Hz or 60 Hz to protect the busbars

and their feeders. The bay protection functions

included in REB500sys are used as

Main 2 / Group 1 - or back-up protection.

The system REB500sys is foreseen for all single

or double busbar configurations (Line variants

L-V1 to L-V7 and Transformer variant TV1

to T-V4). In 1½ breaker configurations,

variant L-V5 can be used for the bay level

functions autoreclosure and synchrocheck.

The capacity is sufficient for up to 60 feeders

(bay units) and a total of 32 busbar zones.

The REB500sys detects all bus faults in solidly

and low resistive-grounded power systems,

all kind of phase faults in ungrounded

and compensated power systems as well as

feeder faults in solidly, low resistive-grounded,

compensated and ungrounded power systems.

The protection operates selectively for all

faults inside the zone of protection and

remains reliably stable for all faults outside the

zone of protection.

REB500sys is perfectly suited for retrofit concepts

and stepwise upgrades. The bay unit is

used as a stand-alone unit for bay protection

functions (e.g. line protection, autoreclosure

and synchrocheck or 2- and 3 winding transformer

protection or autonomous T-zone protection).

The central unit can be added at a

later stage for full busbar and breaker failure

protection functionality.

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 patented

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 output

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 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 binary and analog 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),

bay protection (Main 2 or back-up bay protections)

as well as the event and disturbance

recording.

High-speed distance protection

• Overcurrent or underimpedance starters

with polygonal characteristic

• Five distance zones (polygon for forwards

and reverse measurement)

• Load-compensated measurement

• Definite time overcurrent back-up protection

(short-zone protection)

• System logic

- switch-onto-fault

- overreach zone

• Voltage transformer circuit supervision

• Power swing blocking function

• HF teleprotection. The carrier-aided

schemes include:

- permissive underreaching transfer tripping

- permissive overreaching transfer tripping

- blocking scheme with echo and transient

blocking functions

• Load-compensated measurement

- fixed reactance slope

- reactance slope dependent on load

value and direction (ZHV<)

• Parallel line compensation

• Phase-selective tripping for single and

three-pole autoreclosure

• Four independent, user-selectable setting

groups.

In the supervision mode the active and reactive

power with the respective energy direction

is displayed by the HMI500.

Autoreclosure

The autoreclosure function permits up to four

three-phase autoreclosure cycles. The first

cycle can be single phase or three-phase.

If the REB500sys autoreclosure function is

employed, it can be used as a back-up for the

autoreclosure realized externally (separate

equipment or in the Main 1 protection).

When the autoreclosure function is realized

outside of REB500sys, all input and output

signals required by the external autoreclosure

equipment are available in order to guarantee

correct functionality.

Synchrocheck

The synchrocheck function determines the difference

between the amplitudes, phase

angles and frequencies of two voltage vectors.

The synchrocheck function also contains

checks for dead line and dead bus.

Transformer differential protection

• For two- and three-winding transformers

• Auto transformers

• Three-phase function

• Current-adaptive characteristic

• High stability for external faults and current

transformer saturation

• No auxiliary transformers necessary

because of vector group and CT ratio compensation

• Inrush restraint using 2nd harmonic

The transformer differential protection function

can also be used as an autonomous T-zone

protection in a 1½ breaker scheme.

Thermal overload

This function protects the insulation against

thermal stress. This protection function is normally

equipped with two independently set

levels and is used when oil overtemperature

detectors are not installed.

Peak value over- and undercurrent protection

These functions are used for current monitoring

with instantaneous response and where

insensitivity to frequency is required.

Peak value over- and undervoltage protection

This function is used for voltage monitoring

with instantaneous response and where insensitivity

to frequency is required.

Frequency function

The function is used either as an over-/ underfrequency

protection, or for load-shedding in

the event of an overload. Several stages of

the frequency protection are often needed.

This can be achieved by configuring the frequency

function several times.

Rate of change frequency protection df/dt

This function is used for the static, dynamic

and adaptive load-shedding in power utilities

and industrial distribution systems. The function

supervises the rate-of-change df/dt of one

voltage input channel. Several stages of the

rate-of-change frequency protection are often

needed. This can be achieved by configuring

the rate-of-change frequency function several

times.

Definite time overfluxing protection

This function is primarily intended to protect

the iron cores of transformers against excessive

flux. The function works with a definite

time delay. The magnetic flux is not measured

directly. Instead the voltage/frequency-ratio,

which is proportional to the flux is monitored.

Inverse time overfluxing protection

This function is primarily intended to protect

the iron cores of transformer against excessive

flux. The function works with an inverse

time delay. The inverse curve ca be set by a

table of 10 values and the times t-min and tmax.

The magnetic flux is not measured directly.

Instead the voltage/frequency-ratio,

which is proportional to the flux is monitored.

Power function

This function provides single, or three phase

measurement of the real or apparent power.

The function can be configured for monitoring

reverse, active or reactive power (power

direction setting). Phase angle errors of the

CT/VT inputs can be compensated by setting.

The operating mode can be configured either

to underpower or to overpower protection.

Logics and delay/integrator

These functions allow the user the engineering

of some easily programmable logical functions

and are available as standard also in the

REB500 functionality.

Directional sensitive earth fault protection

for grounded systems

A sensitive directional ground fault function

based on the measurement of neutral current

and voltage is provided for the detection of

high-resistance ground faults in solidly or lowresistance

grounded systems. The scheme

operates either in a permissive or blocking

mode and can be used in conjunction with an

inverse time earth fault overcurrent function.

In both cases the neutral current and voltage

can be derived either externally or internally.

This function works either with the same communication

channel as the distance protection

scheme or with an independent channel.

Directional sensitive earth fault protection

for ungrounded or compensated systems

The sensitive earth fault protection function for

ungrounded systems and compensated systems

with Petersen coils can be set for either

forwards or reverse measurement. The characteristic

angle is set to ±90° 

(U0 · I0 · sin ) in ungrounded systems and to

0° or 180° (U0 · I0 · cos ) for systems with

Petersen coils. The neutral current is always

used for measurement in the case of systems

with Petersen coils, but in ungrounded systems

its use is determined by the value of the

capacitive current and measurement is performed

by a measuring CT to achieve the

required sensitivity. To perform this function

the BU03 with 3I, 1MT and 5U is required.

Definite time over- and undercurrent protection

This function is used as Main 2 or as back-up

function respectively for line, transformer or

bus-tie bays. This function can be activated in

the phase- and/or the neutral current circuit.

Inverse time overcurrent protection

The operating time of the inverse time overcurrent

function reduces as the fault current

increases and it can therefore achieve shorter

operating times for fault locations closer to the

source. Four different characteristics according

to British Standard 142 designated normal

inverse, very inverse, extremely inverse and

long time inverse but with an extended setting

range are provided. The function can be configured

for single phase measurement or a

combined three-phase measurement with

detection of the highest phase current.

Inverse time earth fault overcurrent protection

The inverse time earth fault overcurrent function

monitors the neutral current of the system.

Four different characteristics according

to British Standard 142 designated normal

inverse, very inverse, extremely inverse and

long time inverse but with an extended setting

range are provided.

Directional overcurrent definite / inverse

time protection

The directional overcurrent definite time function

is available either with inverse time or definite

time overcurrent characteristic. This

function comprises a voltage memory for

faults close to the relay location. The function

response after the memory time has elapsed

can be selected (trip or block).

Definite time over- and undervoltage protection

This function works with a definite time delay

with either single or three-phase measurement.