Title: B90 Bus Differential Relay and Breaker Failure Protection
1B90 Bus Differential Relay and Breaker Failure
Protection
- Cost-efficient
- Good performance
- Modern communications capability
- Member of the Universal Relay (UR) family
- Easy integration with other URs
- Common configuration tool for all B90 IEDs
- Proven algorithms (B30) and hardware (UR)
- Expandable
- Two levels of scalability (modules and IEDs)
2Busbar Protection Schemes
GE offer Approach
- High-impedance / linear couplers
- non-configurable busbars
- cheap relay, expensive primary equipment
- Blocking schemes for simple busbars
- Analog low / medium - impedance schemes
- Digital relays for small busbars
- Digital relays for large busbars
- Phase-segregated cost-efficient digital relays
for large busbars
PVD
SPD
Any
BUS
B30
B90
NEW!
3Why Digital Bus Relay?
- Re-configurable busbars require dynamic
assignment of currents to multiple zones - expensive and dangerous when done externally on
secondary currents (analog way) - natural and safe when done in software
- Breaker Fail for re-configurable busbars is
naturally integrated with the bus protection - No need for special CTs (cost)
- Relaxed requirements for the CTs (cost)
- Advantages of digital technology
4Design Challenges for Digital Busbar Relays
- Reliability
- Security
- Immunity to CT saturation
- Immunity to wrong input information
- Large number of inputs and outputs required
- AC inputs (tens or hundreds)
- Trip rated output contacts (tens or hundreds)
- Other output contacts (tens)
- Digital Inputs (hundreds)
- Large processing power required to handle al the
data
5Traditionally Two Distinctive Architectures are
Offered
Distributed Bus Protection
Centralized Bus Protection
- Fits better retrofit installations
- Perceived more reliable
- Potentially faster
- Fits better new installations
- Perceived less reliable
- Slower
6New Architecture Digital Phase-Segregated
Busbar Scheme
- Foundation
- Single-phase IEDs for primary differential
protection - Separate IEDs for Breaker Failure and extra I/Os
- Inter-IED communications for sharing digital
states - Scalability and flexibility
Phase A Protection
iA, vA
TRIPA
Breaker Failure
7B90 Capacity
- Up to 24 circuits in a single zone without
voltage supervision - Multi-IED architecture with each IED built on
modular hardware - Up to 24 AC inputs per B90 IED freely selectable
between currents and voltages (240, 231, 222,
..) - Up to 96 digital inputs per B90 IED
- Up to 48 output contacts per B90 IED
- Flexible allocation of AC inputs, digital inputs
and output contacts between the B90 IEDs
8B90 Features and Benefits
- Maximum number of circuits in one zone 24
- Number of zones 4
- Busbar configuration No limits
- Sub-cycle tripping time
- Security (only 2msec of clean waveforms required
for stability) - Differential algorithm supervised by CT
saturation detection and directional principle - Dynamic bus replica, logic and signal processing
- No need for interposing CTs (ratio matching up to
321) - CT trouble per each zone of protection
- Breaker failure per circuit
- End fault protection (EFP) per circuit
- Undervoltage supervision per each voltage input
- Overcurrent protection (IOC and TOC) per circuit
- Communication, metering and recording
9B90 Applications
- Busbars
- Single
- Breaker-and-a-half
- Double
- Triple
- With and without transfer bus
- Networks
- Solidly grounded
- Lightly grounded (via resistor)
- Ungrounded
10B90 Architecture Overview
- Phase-segregated multi-IED system built on
Universal Relay (UR) platform - Each IED can be configured to include up to six
modules - AC inputs (up to 3 x 24 single phase inputs)
- Contact outputs (up to 6 x 8)
- Digital Inputs (up to 6 X 16)
- Variety of combinations of digital inputs and
output contacts - Fast digital communications between the IEDs for
sharing digital states
11B90 Architecture
- No A/C data traffic
- No need for sampling synchronization,
straightforward relay configuration - all A/C
signals local to a chassis - Data traffic reduced to I/Os
- Direct I/Os (similar to existing UR Remote I/Os)
used for exchange of binary data - Oscillography capabilities multiplied (available
in each IED separately) - Programmable logic (FlexLogic) capabilities
multiplied - SOE capabilities multiplied
- Extra URs in a loop for more I/Os
12B90 Components Protection IEDs
- Modular architecture (from 2 to 9 modules)
- All modules but CPU and PS optional
- Up to 24 AC inputs total (24 currents and no
voltages, through 12 currents and 12 voltages) - Three I/O modules for trip contacts or extra
digital inputs - Features oriented towards AC signal processing
(differential, IOC, TOC, UV, BF current
supervision)
Power Supply
CPU
DSP 1
I/O
DSP 2
I/O
DSP 3
I/O
Comms
B90 is built on UR hardware (4 years of field
experience)
13B90 Components Logic IEDs
- Modular architecture (from 2 to 9 modules)
- All modules but CPU and PS optional
- Up to 96 digital inputs or
- 48 output contacts or
- Virtually any mix of the above
- Features oriented towards logic functions (BF
logic and timers, isolator monitoring and
alarming)
Power Supply
CPU
I/O
I/O
I/O
I/O
I/O
I/O
Comms
B90 is built on UR hardware (4 years of field
experience)
14B90 Scheme for Large Busbars
Dual (redundant) fiber with 3msec delivery time
between neighbouring IEDs. Up to 8 B90s/URs in
the ring
15Security of the B90 Communications
- Dual (redundant) ring each message send
simultaneously in both directions - No switching equipment (direct TX-RX connection)
- Self-monitoring incorporated
- Information re-sent (repeated) automatically
- 32-bit CRC
- Default states of exchanged flags upon loss of
communications (allows developing secure
applications)
16B90 Communications
- The communications feature (Direct I/Os) requires
digital communications card (dual-port 820nmm
LED) - Up to 96 inputs / outputs could be sent /
received - Up to 8 UR IEDs could be interfaced
- When interfacing with other URs, 32 inputs /
outputs are available - The Direct I/O feature is modeled on UCA GOOSE
but is sent over dedicated fiber (not LAN) and is
optimized for speed - User-friendly configuration mechanism is
available - Simple applications do not require communications
17Typical B90 Applications for Large Busbars
7 to 24 feeders
Basic 87 BF for less than 16 feeders
Extended BF for more than 16 feeders
Full version 24 Feeders with BF.
18Typical B90 Applications for Large Busbars
7 to 24 feeders
7 to 24 feeders
19B90 and Small Single Busbars 8-circuit busbar
8 phase-A currents
8 phase-B currents
8 phase-C currents
One B90 IED with 3 zones could protect a single
8-circuit busbar!
Power Supply
CPU
DSP 1
I/O
DSP 2
I/O
DSP 3
I/O
Spare
Diff Zone 1
Diff Zone 2
Diff Zone 3
Two levels of scalability allow flexible
applications
20B90 and Small Single Busbars 12-circuit busbar
Two B90 IEDs with 2 zones could protect a single
12-circuit busbar!
4 phase-B currents
4 phase-C currents
8 phase-A currents
4 phase-A currents
8 phase-B currents
8 phase-C currents
Power Supply
CPU
DSP 1
I/O
DSP 2
I/O
DSP 3
I/O
Spare
Power Supply
CPU
DSP 1
I/O
DSP 2
I/O
Spare
Spare
Spare
Two levels of scalability allow flexible
applications
21B90 and Small Single Busbars 16-circuit busbar
Three B90 single-zone IEDs could protect a single
16..24-circuit busbar!
8 phase-C currents
8 phase-C currents
8 phase-A currents
8 phase-A currents
8 phase-B currents
8 phase-B currents
Power Supply
CPU
DSP 1
I/O
DSP 2
I/O
Spare
Spare
Spare
Power Supply
CPU
DSP 1
I/O
DSP 2
I/O
Spare
Spare
Spare
Power Supply
CPU
DSP 1
I/O
DSP 2
I/O
Spare
Spare
Spare
Two levels of scalability allow flexible
applications
22Applicability to Ungrounded and Lightly Grounded
Systems
- Three phase protection units for phase-to-phase
faults and saturation detection - Fourth unit with AC inputs for zero-sequence
differential protection (fed from split-core or
regular CTs)
Phase B
Phase C
Phase A
IA
IB
IC
Block on external faults
3I0
Ground
B90 can be applied to solidly and lightly
grounded as well as ungrounded systems
23B90 Configuration Program
(1) B90 Protection system is a site
- URPC program used for configuration
- Common setting file for all B90 IEDs
- All B90 can be accessed simultaneously
- Off-line setting files can easily be produced
(2) That includes the required IEDs
(3) Functions available for dealing with all IEDs
simultaneously
24B90 Algorithms
- Bus differential protection
- Dynamic bus replica
- Isolator monitoring and alarming
- End Fault Protection
- Breaker Failure
25CT Saturation Problem
t0 fault inception t2 fault conditions
External fault ideal CTs
26CT Saturation Problem
t0 fault inception t2 fault conditions
External fault CT ratio mismatch
27CT Saturation Problem
t0 fault inception t1 CT saturation time t2
CT saturated
External fault CT saturation
28Differential Protection
- B90 algorithms aimed at
- Improving the main differential function by
providing better filtering, faster response,
better restraining technique, robust switch-off
transient blocking, etc. - Incorporating a saturation detection mechanism
that would recognize CT saturation on external
faults in a fast and reliable manner - Applying a second protection principle namely
phase directional (phase comparison) for better
security
29Bus Differential Function Block Diagram
30B90 Differential Function Theory of Operation
- Definition of the Restraining Current
- Operating Characteristic
- CT Saturation Detector
- Default Tripping Logic
- Customizing the Tripping Logic
31Various Definitions of the Restraining Signal
sum of
scaled sum of
geometrical average
maximum of
32Restraining Current
- The amount of restraint provided by various
definitions is different sometimes significantly
different particularly for multi-circuit
differential elements such as busbar protection - When selecting the slope (slopes) one must take
into account the applied definition of the
restraining signal - The B90 uses the maximum of definition of the
restraining current
33Sum of vs. Max of definitions of restraint
- Sum of approach
- more restraint on external faults less
sensitivity on internal faults - scaled sum of may take into account the actual
number of connected circuits increasing
sensitivity - characteristic breakpoints difficult to set
- Max of approach (B30, B90 and UR in general)
- less restraint on external faults
- more sensitivity on internal faults
- breakpoints easier to set
- better handles situations when one CT may
saturate completely (99 slope settings possible)
34Differential Function Characteristic
35Differential Function Adaptive Approach
- large currents
- quick saturation possible due to large magnitude
- saturation easier to detect
- security required only if saturation detected
- low currents
- saturation possible due to dc offset
- saturation very difficult to detect
- more security required
36Adaptive Logic
DIF1
DIR
SAT
DIF2
37Adaptive Approach
Dynamic 2-out-of-2, 1-out-of-2 operating mode
2-out-of-2 operating mode
38Directional Principle
DIF1
DIR
SAT
DIF2
39Directional Principle
- Voltage signal is not required
- Internal faults
- all fault (large) currents approximately in
phase - External faults
- one current approximately out of phase
Secondary current ofthe faulted circuit(deep CT
saturation)
40Directional Principle
- Implementation
- step 1 select fault contributors
- A contributoris a circuit carrying significant
amount of current - A circuit is a contributor if its current is
above higher break point - A circuit is a contributor if its current is
above a certain portion of the restraining
current - step 2 check angle between each contributor and
the sum of all the other currents - Sum of all the other currents is the inverted
contributor if the fault is external on external
faults one obtains an angle of 180 degrees - step 3 compare the maximum angle to the
threshold - A threshold is a factory constant of 90 degrees
- An angle shift of more than 90 degrees due to CT
saturation is physically impossible
41External Fault
42Internal Fault
43Saturation Detector
DIF1
DIR
SAT
DIF2
44Saturation Detector
t0 fault inception t1 CT starts to
saturate t2 external fault under heavy CT
saturation conditions
45Saturation Detector The State Machine
46Saturation Detector
- Operation
- The SAT flag WILL NOT be set during internal
faults whether or not any CTs saturate - The SAT flag WILL be SET during external faults
whether or not any CTs saturate - By design the SAT flag is NOT used to block the
relay but to switch to 2-out-of-2 operating
principle
47Examples External Fault
48Examples Internal Fault
49User-Modified Tripping Logic
- All the key logic flags (DIFferential,
SATuration, DIRectional) are available as
FlexLogicTM operands with the following meanings - BUS BIASED PKP - differential characteristic
entered - BUS SAT - saturation (external fault) detected
- BUS DIR - directionality confirmed (internal
fault) - FlexLogicTM can be used to override the default
87B logic - Example 2-out-of-2 operating principle with
extra security applied to the differential
principle
50Dynamic Bus Replica
- Dynamic bus replica mechanism is provided by
associating a status signal with each current of
a given differential zone - Each current can be inverted prior to configuring
into a zone (tie-breaker with a single CT) - The status signal is a FlexLogicTM operand
(totally user programmable) - The status signals are formed in FlexLogicTM
including any filtering or extra security checks
from the positions of switches and/or breakers
as required - Bus replica applications
- Isolators
- Tie-Breakers
- Breakers
51Dynamic Bus Replica - Isolators
- Reliable Isolator Closed signal is composed
- The Isolator Position signal
- Decides whether the associated current is to be
included into differential calculations - Decides whether the associated breaker is to be
tripped - For maximum safety
- Both normally open and normally closed contacts
are used - Isolator alarm is established under discrepancy
conditions - Isolator position to be sorted out under
non-valid combinations of the auxiliary contacts
(open-open, closed-closed) - Switching operations in the substation shall be
inhibited until the bus image is recognized with
100 accuracy - Optionally the 87B may be inhibited from the
isolator alarm
52Dynamic Bus Replica - Isolators
53Dynamic Bus Replica Isolator Positions and
Differential Protection
Up to 96 auxuliary switches wired here Isolator
Monitoring function configured here
54Dynamic Bus Replica Tie-Breakers Two-CT
Configuration
Z1
Z2
TB
- Overlapping zones no blind spots
- Both zones trip the Tie-Breaker
- No special treatment of the TB required in terms
of its status for Dynamic Bus Replica (treat as
regular breaker see next section)
55Dynamic Bus Replica Tie-Breakers Tie-Breakers
Single-CT Configuration
Z1
Z2
TB
- Both zones trip the Tie-Breaker
- Blind spot between the TB and the CT
- Fault between TB and CT is external to Z2
- Z1 no special treatment of the TB required
(treat as regular CB) - Z2 special treatment of the TB status required
- The CT must be excluded from calculations after
the TB is opened - Z2 gets extended (opened entirely) onto the TB
56Tie-Breakers Single-CT Configuration
expand
- Sequence of events
- Z1 trips and the TB gets opened
- After a time delay the current from the CT shall
be removed from Z2 calculations - As a result Z2 gets extended up to the opened TB
- The Fault becomes internal for Z2
- Z2 trips finally clearing the fault
57Dynamic Bus Replica Breakers Bus-side CTs
CT
CB
- Blind spot exists between the CB and CT
- CB is going to be tripped by line protection
- After the CB gets opened, the current shall be
removed from differential calculations (expanding
the differential zone up to the opened CB) - Relay configuration required identical as for
the Single-CT Tie-Breaker
58Dynamic Bus Replica Breakers Line-side CTs
CB
CT
- Over-trip spot between the CB and CT when the
CB is opened - When the CB gets opened, the current shall be
removed from differential calculations
(contracting the differential zone up to the
opened CB) - Relay configuration required identical as for a
Single-CT Tie-Breaker, but.
59Dynamic Bus Replica Breakers Line-side CTs
CB
contract
CT
- but.
- A blind spot created by contracting the bus
differential zone - End Fault Protection required B90 provides one
EFP element per current input
60End Fault Protection
(2) Excessive current .
(3) Causes the EFP to operate
(1) The EFP gets armed after the breaker is open
61Breaker Failure Protection
- BF Architecture
- Current supervision residing on protection IEDs
- BFI signal can be generated internally (from
protection IEDs) or externally via communications
or a digital input from any IED - BF logic and timers residing on the logic IED
- Trip contacts distributed freely between various
IEDs - BF Performance
- Reset time of current sensors below 0.7 power
system cycle - Communications delays around 0.2 power system
cycle between any two neighboring IEDs
62Breaker Failure Protection Current Supervision
Up to 24 BF elements configured here
63Breaker Failure Protection Initiate
Up to 24 BF elements configured here
64Breaker Failure Protection Trip Action
Trip command generated here and send to trip
appropraite breakers
65Programmable Logic (FlexLogicTM)
- All B90 IEDs provide for programmable logic
- Distributed logic over fiber-optic communications
(Direct I/Os) - Functions available
- Gates
- Edge detectors
- Latches and non-volatile latches
- Timers
66Disturbance Recording
- All AC inputs automatically recorded
- Programmable sampling rate 8, 16, 32, 64 s/c
- Programmable content (phasor magnitudes and
angles, differential, restraint currents,
frequency, any digital flag) - Programmable number of records vs. record length
- Flexible treatment of old records (overwrite,
preserve) - Programmable trigger
- Programmable pre-/post-trigger windows
- Individual (independent) oscillography
configuration of each B90 IED
67Sequence of Events Recording
- Up to 1040 events per each B90 IED
- Events stamped with 1microsecond resolution
- 0.5 msec scanning rate for digital inputs
- All B90 IEDs synchronized via IRIG-B or SNTP
- All events (except hardware-related alarms) user
programmable - Events can be enabled independently for
- All protection elements
- All digital inputs and contact outputs
- Communications driven signals
- Individual (independent) SOE configuration of
each B90 IED
68Engineering the B90
69B90 Summary
- Cost-efficient
- Good performance
- Modern communications capability
- Member of the Universal Relay (UR) family
- Easy integration with other URs
- Common configuration tool for all B90 IEDs
- Proven algorithms (B30) and hardware (UR)
- Expandable
- Two levels of scalability (modules and IEDs)
70Ordering the B90
- The B90 can be ordered as an engineered product
- The following order code applies to the
engineered B90
B90
B90 Base system
S Single busbar
D Double busbar
T Double busbar with transfer
X Special arrangement
C Cabinet supply
F Frame supply
A RS485 RS485 (ModBus RTU, DNP)
C RS485 10BaseF (MMS/UCA2, ModBus TCP/IP, DNP)
D RS485 redundant 10BaseF (MMS/UCA2, ModBus, TCP/IP, DNP)
H 125/250, AC/DC
L 24-48V (DC only)
Specify the number of lines bus couplers (two digits)
0 Without Breaker Fail
B With Breaker Fail
0 Without End Fault Protection
E With End Fault Protection
00 Sequential number
71How to Order
- International 1 905 294 6222
- Europe 34 94 485 88 00
- Email info.pm_at_indsys.ge.com
- Web http//www.GEindustrial.com/pm