1. B90 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)

2. Busbar Protection Schemes
GE offer Approach
PVD
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
SPD
Any
BUS
B30
B90
NEW!

3. natural and safe when done “in software”
Why 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

4. Design 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

5. Traditionally 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

6. New Architecture – Digital Phase-Segregated Busbar Scheme
Phase A Protection
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
iA, vA
TRIPA
iB, vB
Phase B Protection
TRIPB
iC, vC
Phase C Protection
TRIPC
Breaker Failure

7. Up to 24 circuits in a single zone without voltage supervision
B90 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 (24+0, 23+1, 22+2, ..)
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

8. B90 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 32:1)
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

9. With and without transfer bus Networks: Solidly grounded
B90 Applications
Busbars:
Single
Breaker-and-a-half
Double
Triple
With and without transfer bus
Networks:
Solidly grounded
Lightly grounded (via resistor)
Ungrounded

10. B90 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

11. B90 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

12. B90 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)
8 AC single-phase inputs
8 AC single-phase inputs
8 AC single-phase inputs
Other UR-based IEDs
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)

13. B90 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)
Other UR-based IEDs
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)

14. B90 Scheme for Large Busbars
Dual (redundant) fiber with 3msec delivery time between neighbouring IEDs. Up to 8 B90s/URs in the ring
Phase A AC signals and trip contacts
Phase B AC signals and trip contacts
Phase C AC signals and trip contacts
Digital Inputs for isolator monitoring and BF

15. Security 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)

16. Up to 96 inputs / outputs could be sent / received
B90 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

17. Typical 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.

18. Typical B90 Applications for Large Busbars
7 to 24 feeders
7 to 24 feeders

19. B90 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

20. B90 and Small Single Busbars – 12-circuit busbar
Two B90 IEDs with 2 zones
could protect a single
12-circuit busbar!
8 phase-A currents
4 phase-A currents
4 phase-B currents
8 phase-B currents
8 phase-C currents
4 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

21. B90 and Small Single Busbars – 16-circuit busbar
Three B90 single-zone IEDs
could protect a single
circuit busbar!
8 phase-A currents
8 phase-A currents
8 phase-B currents
8 phase-B currents
8 phase-C currents
8 phase-C 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

22. Applicability 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 A
Phase B
Phase C IA IB IC
Block on external faults
3I0
Ground
B90 can be applied to solidly and lightly grounded as well as ungrounded systems

23. B90 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

24. Bus differential protection Dynamic bus replica
B90 Algorithms
Bus differential protection
Dynamic bus replica
Isolator monitoring and alarming
End Fault Protection
Breaker Failure

25. External fault: ideal CTs
CT Saturation Problem
t0 – fault inception
t2 – fault conditions
External fault: ideal CTs t0 t2

26. External fault: CT ratio mismatch
CT Saturation Problem
t0 – fault inception
t2 – fault conditions
External fault: CT ratio mismatch t0 t2

27. External fault: CT saturation
CT Saturation Problem
t0 – fault inception
t1 – CT saturation time
t2 – CT saturated t2
External fault: CT saturation t0 t1

28. Differential 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

29. Bus Differential Function – Block Diagram

30. B90 Differential Function – Theory of Operation
Definition of the Restraining Current
Operating Characteristic
CT Saturation Detector
Default Tripping Logic
Customizing the Tripping Logic

31. Various Definitions of the Restraining Signal
“sum of”
“scaled sum of”
“geometrical average”
“maximum of”

32. The B90 uses the “maximum of” definition of the restraining 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

33. “Sum 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)

34. Differential Function – Characteristic

35. Differential 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

36. Adaptive Logic
DIF1
AND OR
TRIP
DIR OR
AND
SAT
DIF2

37. Adaptive Approach
Dynamic 2-out-of-2,
1-out-of-2 operating
mode
2-out-of-2
operating
mode

38. Directional Principle
DIF1
AND OR
TRIP
DIR OR
AND
SAT
DIF2

39. Directional 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 of the faulted circuit (deep CT saturation)

40. Directional Principle
Implementation:
step 1: select fault “contributors”
A “contributor”is 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

41. External Fault

42. Internal Fault

43. Saturation Detector
DIF1
AND OR
TRIP
DIR OR
AND
SAT
DIF2

44. t2 t1 t0 t0 fault inception t1 CT starts to saturate
t2 external fault under heavy CT saturation conditions
Saturation Detector t2 t0 t1

45. Saturation Detector – The State Machine
NORMAL
SAT := 0
The differential
current below the
first slope for
certain period of
time
saturation
condition
EXTERNAL
FAULT
SAT := 1
The differential-
restraining trajectory
out of the differential
characteristic for
certain period of time
The differential
characteristic
entered
EXTERNAL
FAULT & CT
SATURATION
SAT := 1

46. Saturation 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

47. Examples – External Fault

48. Examples – Internal Fault
The Figure presents the same signals but for the case of an internal fault. The B30 trips in 10 ms (fast form-C output contact).

49. User-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:

50. The status signal is a FlexLogicTM operand (totally user programmable)
Dynamic 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

51. Dynamic 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

52. Dynamic Bus Replica - Isolators
Isolator Open Auxiliary Contact
Isolator Closed Auxiliary Contact
Isolator Position
Alarm
Block Switching
Off On
CLOSED No
LAST VALID
After time delay until acknowledged
Until Isolator Position is valid
OPEN

53. Dynamic Bus Replica – Isolator Positions and Differential Protection
Phase A AC signals wired here, bus replica configured here
Isolator Position
Isolator Position
Phase B AC signals wired here, bus replica configured here
Phase C AC signals wired here, bus replica configured here
Isolator Position
Isolator Position
Up to 96 auxuliary switches wired here; Isolator Monitoring function configured here

54. Dynamic Bus Replica – Tie-Breakers: Two-CT ConfigurationZ1 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)

55. Both zones trip the Tie-Breaker Blind spot between the TB and the CT
Dynamic 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

56. Tie-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

57. Dynamic Bus Replica – Breakers: Bus-side CTs
Blind spot for
bus protection 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

58. Dynamic Bus Replica –Breakers: Line-side CTs
“Over-trip” spot for
bus protection 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….

59. Dynamic Bus Replica –Breakers: Line-side CTs
Blind spot for
bus protection 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

60. End Fault Protection (2) Excessive current ….
(3) Causes the EFP to operate
(1) The EFP gets armed after the breaker is open

61. Breaker 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

62. Breaker Failure Protection – Current Supervision
Phase A AC signals wired here, current status monitored here
Current Status
Current Status
Phase B AC signals wired here, current status monitored here
Phase C AC signals wired here, current status monitored here
Current Status
Current Status
Up to 24 BF elements configured here

63. Breaker Failure Protection – Initiate
BFI
Phase A AC signals wired here, current status monitored here
BF Initiate
BF Initiate
Phase B AC signals wired here, current status monitored here
Phase C AC signals wired here, current status monitored here
BF Initiate
BF Initiate
BFI
Up to 24 BF elements configured here

64. Breaker Failure Protection – Trip Action
Phase A AC signals wired here, current status monitored here
Trip Command
Trip Command
Trip
Trip
Phase B AC signals wired here, current status monitored here
Phase C AC signals wired here, current status monitored here
Trip Command
Trip Command
Trip
Trip command generated here and send to trip appropraite breakers

65. Programmable 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

66. Disturbance 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

67. Sequence 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

68. Engineering the B90 Logic design FlexLogicTM Implementation
Substation one-line and
wiring diagrams

69. Modern communications capability
B90 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)

70. The B90 can be ordered as an engineered product
Ordering the B90
The B90 can be ordered as an engineered product
The following order code applies to the engineered 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)
RS BaseF (MMS/UCA2, ModBus TCP/IP, DNP)
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)
Without Breaker Fail B
With Breaker Fail
Without End Fault Protection E
With End Fault Protection 00
Sequential number

71. How to Order International: +1 905 294 6222 Europe: +34 94 485 88 00
Web: