B90 Bus Differential Relay and Breaker Failure Protection

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

• 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!
3
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

• 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
7
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 (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

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
  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

9
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)

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)

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
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
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!
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
21
B90 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
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 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
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
B90 Algorithms

• Bus differential protection
• Dynamic bus replica
• Isolator monitoring and alarming
• End Fault Protection
• Breaker Failure

25
CT Saturation Problem
t0 fault inception t2 fault conditions
External fault ideal CTs
26
CT Saturation Problem
t0 fault inception t2 fault conditions
External fault CT ratio mismatch
27
CT Saturation Problem
t0 fault inception t1 CT saturation time t2
CT saturated
External fault CT saturation
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
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
DIR
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
DIR
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 ofthe faulted circuit(deep CT
saturation)
40
Directional 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

41
External Fault
42
Internal Fault
43
Saturation Detector
DIF1
DIR
SAT
DIF2
44
Saturation Detector
t0 fault inception t1 CT starts to
saturate t2 external fault under heavy CT
saturation conditions
45
Saturation Detector The State Machine
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
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
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
53
Dynamic Bus Replica Isolator Positions and
Differential Protection
Up to 96 auxuliary switches wired here Isolator
Monitoring function configured here
54
Dynamic 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)

55
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
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
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
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
Up to 24 BF elements configured here
63
Breaker Failure Protection Initiate
Up to 24 BF elements configured here
64
Breaker Failure Protection Trip Action
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
69
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
Ordering 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
71
How 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