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Bus Protection Seminar Material - General Electric GE
Bus Differential Protection Seminar June 2015 AB/BC
JC Theron
GE Digital Energy Multilin
Page 2 2015-01-15 Rev. 2 JCT
Presentation Outline
Introduction to Bus Protection
Bus Arrangements and Components
Protection Techniques
CT Saturation
High Impedance Bus Differential Protections
Low Impedance Bus Differential Protections
GE Digital Energy Multilin
Page 3 2015-01-15 Rev. 2 JCT
Presentation Outline
GEs Multilin Bus Protection Portfolio
B30, B90 & B95Plus Application Considerations
Advanced Application Topics
B90 & B95Plus Application Examples
GE Digital Energy Multilin
Page 4 2015-01-15 Rev. 2 JCT
Introduction to Bus Protection
GE Digital Energy Multilin
Page 5 2015-01-15 Rev. 2 JCT
Challenges to Bus Zone Protection
High Fault Current Levels
Large dynamic forces can place mechanical stress on busbars and result in physical damage to equipment therefore fast clearing times are required.
High fault currents can lead to CT saturation, particularly for external faults, which may lead to mal-operation of the bus protection.
Mal-Operation of Bus Protections Have Significant Impact
Loss of customer loads may damage both customer assets as well as customer perception of the utility.
Detrimental impact on industrial processes
System voltage levels and corresponding system stability may be adversely affected.
Best Case: Remedial Action Schemes (load shedding)
Worst Case: Partial or Total System Collapse (wide-spread blackout)
Bus Protection Must be Dependable and Secure, With Emphasis on Security
GE Digital Energy Multilin
Page 6 2015-01-15 Rev. 2 JCT
Challenges to Bus Zone Protection Continued
Many Different Bus Topologies
Many switchyard configurations possible.
Many different CT placements possible.
Single Bus, Double Bus (Single and Double Breaker), Main and Transfer Bus, Breaker-and-a-Half and hybrids
Buses may Reconfigure at Any Time
Different apparatus may be connected/disconnected from a given bus.
Switching may happen from any number of sources
Manually from human operator action (e.g. equipment maintenance)
Automatically from other protections, Wide-Area Special Protections, Remedial Action Schemes, Auto-Restoration/Auto-Transfer Schemes
Bus Protection Must Adapt Automatically (No User Intervention) and in Real-Time, Based on Bus Configuration
GE Digital Energy Multilin
Page 7 2015-01-15 Rev. 2 JCT
Arc flash energy reduction:
Relay operating times of 12 24 mS will reduce energy to level 2 in most MV cases
No impact on system coordination
Always in operation without any special action required by workers
Faster return to service following a bus fault:
Fast operating time minimizes physical damage
Shorter repair times
High-Speed Bus Protection Advantages
GE Digital Energy Multilin
Page 8 2015-01-15 Rev. 2 JCT
Seeing increased specification of bus differential on LV switchgear for arc flash mitigation CT performance is usually too poor for true bus differential
Limited space for hi C-rated CTs
Very high available SC currents (50 60 KA typical)
No notable advantage of high versus low impedance differential
Zone selective interlock is best current solution
May see non-iron core current sensor technology in future
Rogowski coils
Fiber optic sensors
Low Voltage Bus Differential
GE Digital Energy Multilin
Page 9 2015-01-15 Rev. 2 JCT
Bus Arrangements and Components
GE Digital Energy Multilin
Page 10 2015-01-15 Rev. 2 JCT
1 2 3 n-1 n
ZONE 1
- - - -
Distribution and lower transmission voltage levels
No operating flexibility Fault on the bus trips all circuit
breakers
ZONE 1ZONE 2
Lower transmission voltages Limited operating flexibility
ZONE 1
ZONE 2
Very common arrangement at US West Coast substations
Transmission and distribution voltage levels
Breaker maintenance without circuit removal
Fault on a bus disconnects only the circuits being connected to that bus
Multiple bus sections - single breaker with bus tie
Single bus - single breaker
Double bus - single breaker with bus tie
GE Digital Energy Multilin
Page 11 2015-01-15 Rev. 2 JCT
Typical Industrial Single Bus
GE Digital Energy Multilin
Page 12 2015-01-15 Rev. 2 JCT
Typical Industrial Double Bus
GE Digital Energy Multilin
Page 13 2015-01-15 Rev. 2 JCT
ZONE 1
ZONE 2
Very high operating flexibility Transfer bus for breaker
maintenance
ZONE 1
MAIN BUS
TRANFER BUS
Increased operating flexibility A bus fault requires tripping all
breakers Transfer bus for breaker
maintenance
Main and Transfer buses
Double bus single breaker with transfer bus
GE Digital Energy Multilin
Page 14 2015-01-15 Rev. 2 JCT
ZONE 1
ZONE 2
High operating flexibility Line protection covers the part
between two CTs Fault on a bus does not disturb
the power of the circuits
ZONE 1
ZONE 2
Used on higher voltage levels More operating flexibility Requires more breakers Middle sections covered by the
line protection
Double bus - double breaker
Breaker-and-a-half bus
GE Digital Energy Multilin
Page 15 2015-01-15 Rev. 2 JCT
Higher voltage levels High operating flexibility with
minimum breakers Separate bus protection not
required, as the line protections cover overlap bus parts
B1 B2
TB1
L1 L2
L3 L4
TB1
Ring bus
GE Digital Energy Multilin
Page 16 2015-01-15 Rev. 2 JCT
Bus Components
BUS 1
BUS 2
ISO4
CB 2
CT2
C2
ISO5
ISO1
CB 1
CT1
C1
ISO2
ISO 3
CT12
CT13
CB 12
CB 11 CT11
CT10CB 10
ISO25
CB 9
CT9
C9
ISO26
ISO28
ISO29
ISO 6 ISO27
Feeder isolators
Feeder breaker
Feeder CTs
GE Digital Energy Multilin
Page 17 2015-01-15 Rev. 2 JCT
Bus Components
BUS 1
BUS 2
ISO4
CB 2
CT2
C2
ISO5
ISO1
CB 1
CT1
C1
ISO2
ISO 3
CT12
CT13
CB 12
ISO25
CB 9
CT9
C9
ISO26
ISO28
ISO29
ISO 6 ISO27
CT11CB 11
CT10CB 10
Section breakers
Section breaker CTs
Coupler breaker isolators
Coupler breaker
Coupler breaker CTs
GE Digital Energy Multilin
Page 18 2014-09-15 Rev. 1 JCT
Protection Techniques
GE Digital Energy Multilin
Page 19 2015-01-15 Rev. 2 JCT
Bus Zone Protection Techniques
Various existing implementations:
Unrestrained Differential
Interlocking/Blocking Schemes
High Impedance Differential
Low Impedance Percent Differential
All Bus Zone protections essentially operate based on Kirchoffs Law for Currents:
The sum of all currents entering a node must equal zero.
The only variation is on how this is implemented.
GE Digital Energy Multilin
Page 20 2015-01-15 Rev. 2 JCT
Unrestrained Differential (Overcurrent)
Differential current created by physically summing CTs
CT ratio matching required (auxiliary CTs)
External faults may cause CT saturation, leading to spurious differential currents in the bus protection
Intentional time delay added to cope with CT saturation effects
Unrestrained differential function useful for microprocessor-based protections (check zone)
51
Intentional Time Delay means No Fast Zone Clearance
GE Digital Energy Multilin
Page 21 2015-01-15 Rev. 2 JCT
Interlocking/Blocking Schemes
Blocking signals generated by downstream protections (usually instantaneous overcurrent)
Simple inst. overcurrent protection with short intentional time delay
Need to wait for blocking signals
Usually inverse timed backup provided
Timed backup may be tricked by slow clearance of downstream faults.
Blocking can be done via hardwire or communications (e.g GSSE/GOOSE, dedicated communications)
Technique Limited to Radial Circuits with Negligible Backfeed
50
50 50 50 50 50
BL
OC
K
GE Digital Energy Multilin
Page 22 2015-01-15 Rev. 2 JCT
High Impedance Differential (Overvoltage)
Operating signal created by connecting all CT secondaries in parallel
CTs must all have the same ratio
Must have dedicated CTs
Overvoltage element operates on voltage developed across resistor connected in secondary circuit
Requires varistors or AC shorting relays to limit energy during faults
Accuracy dependent on secondary circuit resistance
Usually requires larger CT cables to reduce errors higher cost
Cannot Easily be Applied to Reconfigurable Buses and Offers no Advanced Functionality (Oscillography, Breaker Fail).
59
GE Digital Energy Multilin
Page 23 2015-01-15 Rev. 2 JCT
High
Impedance Bus Differential
Relay
CB n CB 3 CB 2 CB 1
I1 I2 I3 In
i1
i2
i3
in
I1 + I2 + I3 + + In = Id = 0 The vectorial sum of all primary currents in and out of the bus equals zero
i1 + i2 + i3 + . + in = id = 0 The vectorial sum of all CT secondary currents (assuming same CT ratio and no CT saturation) in and out of the bus equals zero
v1 +v2 + v3 + + vn = vd = 0 The vectorial sum of all voltages induced on all CT secondary windings during normal load or external fault (no CT saturation) equals zero
vd = 0
id = 0
None of the above equations hold true during internal fault or external fault with CT saturation
+ - - +
High Impedance Bus Protection - General Philosophy
GE Digital Energy Multilin
Page 24 2015-01-15 Rev. 2 JCT
High Impedance Differential (Overvoltage/current)
Operating signal created by connecting all CT secondaries in parallel
CTs same ratio, class, saturation curve and burden (including same CT leads)
Must have dedicated CTs
Overvoltage element operates on voltage across resistor in secondary circuit
Requires varistors and/or AC shorting relays to limit
energy during faults
Model HID32
or HID31
B30 Relay
GE Digital Energy Multilin
Page 25 2015-01-15 Rev. 2 JCT
High Impedance Differential (Overvoltage/current) Settings Calculations
Operating signal measured can be Voltage or Current: Voltage:
Current:
Where VS = pickup setting of voltage element (if voltage is used)
IR = pickup setting of the current differential element (if current is used)
RS = DC Resistance of fault CT secondary windings and leads to terminals.
RL = single conductor DC resistance of CT cable for one way run from CT housing terminal to measuring element
P = 1 for three phase faults; 2 for single phase to ground faults
IF = external fault current primary RMS value
N = CT ratio
1.6 = margin factor
RE = stabilizing resistance (2000 Ohm if the HID is used)
GE Digital Energy Multilin
Page 26 2015-01-15 Rev. 2 JCT
Low Impedance Percent Differential
Individual currents sampled by protection and summated digitally CT ratio matching done internally (no auxiliary CTs)
Dedicated CTs not necessary
Additional algorithms improve security of percent differential characteristic during CT saturation
Dynamic bus replica allows application to reconfigurable buses Done digitally with logic to add/remove current inputs from differential computation
Switching of CT secondary circuits not required
Low secondary burdens
Additional functionality available without additional devices Digital oscillography
Time-stamped event recording
Breaker Failure
Can be Applied to Reconfigurable Buses and Secure from CT Saturation, with Additional Useful Functionality.
GE Digital Energy Multilin
Page 27 2015-01-15 Rev. 2 JCT
Digital Differential Algorithm Goals
Improve the main differential algorithm operation
Better filtering
Faster response
Better restraint techniques
Switching transient blocking
Provide dynamic bus replica for reconfigurable busbars
Dependably detect CT saturation in a fast and reliable manner, especially for external faults
Apply additional security to the main differential algorithm to prevent incorrect operation
External faults with CT saturation
CT secondary circuit trouble (e.g. short circuits)
GE Digital Energy Multilin
Page 28 2015-01-15 Rev. 2 JCT
CT Saturation
GE Digital Energy Multilin
Page 29 2015-01-15 Rev. 2 JCT
CT Saturation Concepts
CT saturation depends on a number of factors
Physical CT characteristics (size, rating, winding resistance, saturation voltage)
Connected CT secondary burden (wires + relays)
Primary current magnitude, DC offset (system X/R)
Residual flux in CT core
Actual CT secondary currents may not behave in the same manner as the ratio (scaled primary) current during faults
End result is spurious differential current appearing in the summation of the secondary currents which may cause differential
elements to operate if additional security is not applied
GE Digital Energy Multilin
Page 30 2015-01-15 Rev. 2 JCT
CT Saturation
Ratio Current CT Current
Ratio Current CT Current
No DC Offset
Waveform remains fairly symmetrical
With DC Offset
Waveform starts off being asymmetrical, then symmetrical in steady state
GE Digital Energy Multilin
Page 31 2015-01-15 Rev. 2 JCT
CT Saturation External Fault with Ideal CTs
Fault starts at t0
Steady-state fault conditions occur at t1
diffe
ren
tia
l
restrainingt0
t1
Ideal CTs have no saturation or mismatch thus produce no differential current
GE Digital Energy Multilin
Page 32 2015-01-15 Rev. 2 JCT
CT Saturation External Fault with Actual CTs
Fault starts at t0
Steady-state fault conditions occur at t1
diffe
ren
tia
l
restrainingt0
t1
Actual CTs do introduce errors thus produce some differential current (without CT saturation)
GE Digital Energy Multilin
Page 33 2015-01-15 Rev. 2 JCT
CT Saturation External Fault with CT Saturation
Fault starts at t0, CT begins to saturate at t1
CT fully saturated at t2
diffe
ren
tia
l
restrainingt0
t1
t2
CT saturation causes increasing differential current that may enter the differential element operate region.
t0 fault inception t1 CT saturation time t2 CT saturated
GE Digital Energy Multilin
Page 34 2015-01-15 Rev. 2 JCT
Some Methods of Securing Bus Differential
Block the bus differential for a period of time (intentional delay)
Increases security as bus zone will not trip when CT saturation is present
Prevents high-speed clearance for internal faults with CT saturation or evolving faults
Change settings of the percent differential characteristic (usually Slope 2)
Improves security of differential element by increasing the amount of spurious differential current needed to incorrectly trip
Difficult to explicitly develop settings (Is 60% slope enough? Should it be 75%?)
Apply directional (phase comparison) supervision
Improves security by requiring all currents flow into the bus zone before asserting the differential element
Easy to implement and test
Stable even under severe CT saturation during external faults
GE Digital Energy Multilin
Page 35 2015-01-15 Rev. 2 JCT
High Impedance vs Low Impedance Bus Protection
MDS WiYZTM Bus Protection Applications
High Impedance Low Impedance
Pros Different CT ratios and classes can be used CTs can be shared with other devices With CT Saturation Detection & Directionality
check; Robust on External Faults with CT
Saturation
CT Supervision/monitoring available Additional protection functions available on per-
feeder basis (50/51/50N/51N, 59 and Breaker Fail)
Multiple tripping contacts available No Stabilizing Resistors or Varistor/Metrosils
needed
Dynamic Bus Replica Available IED-functionalities eg SOE, waveform capture Always self-monitored; less maintenance required
Cons Slower than High Impedance, however sub-cycle Dedicated CT Saturation Detection required Settings more complicated Schemes can get very complicated for
large/double busses with Breaker Fail
Pros Used for years wide familiarity (Setting &
Testing)
Exceptional performance External faults with CT Saturation
Low Cost Simple to Set Easy to expand scheme Fast Operating Times for Internal Faults Better in cases with High range of Fault Current
Cons Identical CT ratios, class required (Same B/H &
knee-point voltage) (Cost)
CTs not to be shared with other higher-VA devices dedicated CTs (Potential Cost)
Stabilizing resistors and/or Varistor Metrosils required (Cost & Safety)
Zone selection/switching (Bus Replica) not possible External contact multiplication required No IED-functionalities eg. No capture of Separate
waveforms, events, no communications
Mostly Unmonitored E/M relays without self-checking more regular maintenance required
GE Digital Energy Multilin
Page 37 2015-01-15 Rev. 2 JCT
GEs Multilin Bus Protection Portfolio
GE Digital Energy Multilin
Page 38 2015-01-15 Rev. 2 JCT
GE Multilin Bus Differential Relays
High Impedance Differential
PVD (Electromechanical)
MIB II (single function digital relay)
HID (high impedance module with UR-series (B30))
Low Impedance Digital Differential
B30
B90
B95Plus
B30, B90 and B95Plus have a great deal in common, but do have some significant differences as well
GE Digital Energy Multilin
Page 39 2015-01-15 Rev. 2 JCT
Electro-mechanical Work-horse:
Fast: typical operating time of 16 30 mS Phase packaged (3 required) 100s of thousands in service Still available (expensive) Aging fleet will need replacing due to capacitor failures
High Impedance Bus Protection (PVD)
GE Digital Energy Multilin
Page 40 2015-01-15 Rev. 2 JCT
Comprised of the following:
High-Speed overcurrent module: Differential protection for up to 3
differential currents (phases). High Impedance Module (HID) with Stabilizing Resistors and Voltage Limiters
The high speed overcurrent relay connected in series with the stabilizing resistors provides high speed operation for bus faults involving high-magnitude currents. A voltage limiting element (MOV) is connected in
parallel to avoid excessively high CT secondary voltages that can damage the current inputs after relay operation.
Lockout Relay & Push Button: Mechanical lockout after relay operation and Reset Button. Lockout contacts short CT secondaries. Four additional normally open contacts available for use
High Impedance Bus Protection (MIB)
GE Digital Energy Multilin
Page 41 2015-01-15 Rev. 2 JCT
Comprised of the following:
B30 Relay (alternate: 850)- high speed overcurrent relay (check sensitivity). High Impedance Module (HID) with Stabilizing Resistors and Voltage Limiters
The B30 relay (high speed overcurrent relay) connected in series with the stabilizing resistors provides high speed operation for bus faults involving high-magnitude currents. A voltage limiting element (MOV) is connected in parallel to avoid excessively high CT secondary voltages that can damage the current inputs after relay operation.
Lockout Relay & Push Button: Mechanical lockout after relay operation and Reset Button. Lockout contacts short CT secondaries. Four additional normally open contacts available for use.
+
B30 Relay HID Module
High Impedance Bus Protection (B30 + HID)
GE Digital Energy Multilin
Page 42 2015-01-15 Rev. 2 JCT
Low Impedance Protection: B30 & B90 vs B95Plus
B30 & B90 are members of the Universal Relay (UR) family Common hardware & software
Common added features
Common communications interfaces & protocols
User Programmable Logic (FlexLogic)
B95Plus based on URPlus hardware platform
High Performance (All) Typical Response Time: 12 msec + output contact
Max. Response Time: 16 msec + output contact
Secure for external faults with severe CT saturation
All use the same proven algorithms for ratio compensation, dynamic bus replication, differential calculations, CT saturation detection and differential element security
Proven Hardware. Proven Algorithms.
GE Digital Energy Multilin
Page 43 2015-01-15 Rev. 2 JCT
B30 & B90 What is Different
B30 provides three-phase bus differential protection in a single hardware chassis
All three phase currents from all feeders are connected to a single chassis with multiple DSPs (1 zone), with phase segregation done in software only.
Limited to 6 three-phase current sources (or five current sources and one three-phase voltage source)
Up to six breaker failure elements included
B90 provides hardware-segregated bus differential protection in one or more hardware chassis
DSP modules configured for up to 8 currents (7 currents & 1 voltage) for a single phase
Phase segregation by hardware and software configuration
Minimum configuration: 8 feeders in a single chassis with three DSP modules (4 zones)
Maximum configuration: 24 feeders in three chassis, each with 3 DSPs (4 zones)
Additional I/O, additional Logic, optional breaker failure available
B30 Cost effective protection & metering. B90 Comprehensive and scalable protection.
GE Digital Energy Multilin
Page 44 2015-01-15 Rev. 2 JCT
52
DAU
52
DAU
52
DAU
CU
copper
fiber
Distributed Architecture (B95+):
Data Acquisition Units in the bays
Central Unit processing all the data
Fiber for communication
Sampling synchronization by CU
Easily expanded
52 52 52
CU
copper
Centralized Architecture (B30, B90):
Central Unit processing all the data
Traditional copper cables
CT lead length limitation
Centralized architecture Distributed Architecture
Bus Protection
GE Digital Energy Multilin
Page 45 2015-01-15 Rev. 2 JCT
MAIN PROTECTION
Two Bus Differential (87B) zones:
Restrained and Unrestrained (instantaneous)
Dynamic Bus Replica
Phase IOCs (2 elements only for external check zone and supervision)
VOLTAGE SUPERVISION
Phase Undervoltage (27P)
Neutral & Auxiliary Overvoltage (59N & X)
BACKUP
Phase, Neutral & Ground TOCs (per feeder)
OTHER
Breaker Failure per breaker
CT Trouble (50/74)
FlexElementsTM
Power metering (FW 7.3x)
B30 Protection Features (up to 6 circuits)
GE Digital Energy Multilin
Page 46 2015-01-15 Rev. 2 JCT
B30 Bus Differential Protection - Wiring
GE Digital Energy Multilin
Page 47 2015-01-15 Rev. 2 JCT
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
B90 Low Impedance Bus Protection
24 Circuit Applications
Up to 24 circuits in a single zone without voltage supervision
Multi-IED architecture with each IED built on modular hardware (single to multiple chassis)
GE Digital Energy Multilin
Page 48 2015-01-15 Rev. 2 JCT
MAIN PROTECTION
Four Bus Differential zones:
Restrained (87B)
Unrestrained/instantaneous (50/87)
Dynamic Bus Replica
VOLTAGE SUPERVISION
Phase Undervoltage (27P)
BACKUP
Phase TOC (51) - per feeder
Phase IOCs (50) - per feeder
OTHER
Breaker Failure per breaker (50BF)
CT Trouble (50/74)
B90 Protection Features
GE Digital Energy Multilin
Page 49 2015-01-15 Rev. 2 JCT
8 Circuit Applications
B90 Low Impedance Bus Protection
Different CT Ratio Capability for Each Circuit
Largest CT Primary is Base in Relay
24 Current Inputs 4 Zones
Zone 1 = Phase A Zone 2 = Phase B Zone 3 = Phase C Zone 4 = Not used
GE Digital Energy Multilin
Page 50 2015-01-15 Rev. 2 JCT
Relay 1 - 24 Current Inputs 4 Zones
Zone 1 = Phase A (12 currents) Zone 2 = Phase B (12 currents) Zone 3 = Not used Zone 4 = Not used
CB 12 CB 11
Relay 2 Up to 24 Current Inputs 4 Zones
Zone 1 = Not used Zone 2 = Not used Zone 3 = Phase C (12 currents) Zone 4 = Possibly used for ground TOC
backup
12 Circuit Applications
B90 Low Impedance Bus Protection
Different CT Ratio Capability for Each Circuit Largest CT Primary is Base in Relay
GE Digital Energy Multilin
Page 51 2015-01-15 Rev. 2 JCT
B90 Bus Differential Protection - Wiring
GE Digital Energy Multilin
Page 52 2015-01-15 Rev. 2 JCT
MAIN PROTECTION
Uses Merging Units (BRICKs)
Six Bus Differential zones: Restrained (87B) Unrestrained/instantaneous (50/87) Dynamic Bus Replica
VOLTAGE SUPERVISION
Phase Undervoltage (27P)
BACKUP
Phase TOC (51)- per feeder
Phase IOCs (50)
OTHER
Breaker Failure per bkr (50BF)
CT Trouble (50/74)
B95Plus Protection Features
Reconfigurable multi-section busbar - up to 24 feeders in one chassis
GE Digital Energy Multilin
Page 53 2015-01-15 Rev. 2 JCT
B95Plus System Architecture
GE Digital Energy Multilin
Page 54 2015-01-15 Rev. 2 JCT
B95Plus Bus Differential Protection - Wiring
GE Digital Energy Multilin
Page 55 2015-01-15 Rev. 2 JCT
B95Plus Bus Differential Protection - Wiring
GE Digital Energy Multilin
Page 56 2015-01-15 Rev. 2 JCT
B95Plus Bus Differential Protection - Wiring
Configuration of Bus Differential (87B)
GE Digital Energy Multilin
Page 58 2015-01-15 Rev. 2 JCT
Configuring the Bus Differential Zone
1. Configure the physical CT Inputs CT Primary and Secondary values
Both 5 A and 1 A inputs are supported by the UR hardware (NOT by Brick!)
Ratio compensation done automatically for CT ratio differences up to 32:1
2. Configure AC Signal Sources (B30 and B95Plus)
3. Configure Bus Zone with Dynamic Bus Replica
Bus Zone settings defines the boundaries of the Differential Protection and CT Trouble Monitoring.
GE Digital Energy Multilin
Page 59 2015-01-15 Rev. 2 JCT
The Dynamic Bus (Example 1)
NORTH BUS
SOUTH BUS
CT-7
CT-8
B-7
B-5
B-6
CT-5
CT-6
S-5
S-6
B-4CT-4
S-3
S-4
B-3CT-3
S-1
S-2
B-2CT-2CT-1
B-1
C-1 C-2 C-4
C-3 C-5
GE Digital Energy Multilin
Page 60 2015-01-15 Rev. 2 JCT
The Dynamic Bus Replica B30 Configuration (Example 1)
Bus Zone Source A CT-1
Bus Zone Status A On (Always Included in Bus Zone)
Bus Zone Source B CT-2
Bus Zone Status B S-1 (Only Included in Bus Zone if S-1 Closed)
Bus Zone Source C CT-3
Bus Zone Status C S-3
Bus Zone Source D CT-4
Bus Zone Status D S-5
Bus Zone Source E CT-5
Bus Zone Status E On
Bus Zone Source F CT-8
Bus Zone Status F On
GE Digital Energy Multilin
Page 61 2015-01-15 Rev. 2 JCT
Bus Differential Block Diagram
GE Digital Energy Multilin
Page 62 2015-01-15 Rev. 2 JCT
Definitions of Restraint Signals
maximum of
geometrical average
scaled sum of
sum of nR iiiii ...321
nR iiiin
i ...1
321
nR iiiiMaxi ,...,,, 321
nnR iiiii ...321
GE Digital Energy Multilin
Page 63 2015-01-15 Rev. 2 JCT
Sum Of Versus Max Of Restraint Methods
Sum Of Approach
More restraint on external faults; less sensitive for internal faults
Scaled-Sum Of approach takes into account number of connected circuits and may increase sensitivity
Breakpoint settings for the percent differential characteristic more difficult to set
Max Of Approach
Less restraint on external faults; more sensitive for internal faults
Breakpoint settings for the percent differential characteristic easier to set
Better handles situation where one CT may saturate completely (99% slope settings possible)
B30, B90 (and UR in General) and B95Plus Use the Max Of Definition for Restraint Quantities.
GE Digital Energy Multilin
Page 64 2015-01-15 Rev. 2 JCT
Bus Differential Adaptive Approach d
iffe
ren
tia
l
restraining
Region 1
(low differential
currents)
Region 2
(high differential
currents)
Region 1 (DIFL)
Low current magnitudes
CT saturation unlikely, due to DC offset
Region 2 (DIFH)
High current magnitudes Quick CT saturation likely
CT saturation easy to detect
GE Digital Energy Multilin
Page 65 2015-01-15 Rev. 2 JCT
Bus Differential Adaptive Logic Diagram
DIFL
DIR
SAT
DIFH
OR
AN
D
OR
87B BIASED OP
AN
D
GE Digital Energy Multilin
Page 66 2015-01-15 Rev. 2 JCT
Phase Comparison Principle Continued
BLOCK
OPERATE
BLOCK
pD
p
II
Ireal
pD
p
II
Iimag
Ip
ID
- Ip
External Fault Conditions
OPERATE
BLOCK
BLOCK
pD
p
II
Ireal
pD
p
II
Iimag
Ip
ID
- Ip
Internal Fault Conditions
OPERATE
OPERATE
Secondary Current of
Faulted Circuit
(Severe CT Saturation)
No Voltages are required or needed
GE Digital Energy Multilin
Page 67 2015-01-15 Rev. 2 JCT
CT Saturation Redux
Fault starts at t0, CT begins to saturate at t1
CT fully saturated at t2
diffe
ren
tia
l
restrainingt0
t1
t2
GE Digital Energy Multilin
Page 68 2015-01-15 Rev. 2 JCT
CT Saturation Detector Operating Principles
The 87B SAT flag WILL NOT be set during internal faults, regardless of whether or not any of the CTs saturate.
The 87B SAT flag WILL be set during external faults, regardless of whether or not any of the CTs saturate.
By design, the 87B SAT flag WILL force the relay to use the additional 87B DIR phase comparison for Region 2
The Saturation Detector WILL NOT Block the Operation of the Differential Element it will only Force 2-out-of-2 Operation
GE Digital Energy Multilin
Page 69 2015-01-15 Rev. 2 JCT
CT Saturation Detector - Examples
The oscillography records on the next two slides were captured from a B30 relay under test on a real-time digital power system simulator
First slide shows an external fault with deep CT saturation (~1.5 msec of good CT performance)
SAT saturation detector flag asserts prior to BIASED PKP bus differential pickup
DIR directional flag does not assert (one current flows out of zone), so even though bus differential picks up, no trip results
Second slide shows an internal fault with mild CT saturation
BIASED PKP and BIASED OP both assert before DIR asserts
CT saturation does not block bus differential
More examples available (COMTRADE files) upon request
GE Digital Energy Multilin
Page 70 2015-01-15 Rev. 2 JCT
The bus differential
protection element
picks up due to heavy
CT saturation
The CT saturation flag
is set safely before the
pickup flag
The
directional flag
is not set
The element
does not
maloperate
Despite heavy CT saturation the external fault current is seen in the opposite direction
CT Saturation Example External Fault
0.06 0.07 0.08 0.09 0.1 0.11 0.12 -200
-150
-100
-50
0
50
100
150
200
time, sec
cu
rre
nt,
A
~1 ms
GE Digital Energy Multilin
Page 71 2015-01-15 Rev. 2 JCT
The bus differential
protection element
picks upThe saturation
flag is not set - no
directional
decision required
The element
operates in
10ms
The
directional
flag is set
All the fault currents
are seen in one
direction
CT Saturation Internal Fault Example
GE Digital Energy Multilin
Page 72 2015-01-15 Rev. 2 JCT
B30, B90 & B95Plus Application Considerations
GE Digital Energy Multilin
Page 73 2015-01-15 Rev. 2 JCT
B90 Applications for Large Busbars
1 2 3 23 24
ZONE 1
Single Bus Single Breaker
1 2 3 21 22
ZONE 1
ZONE 2
23 24
Double Bus Single Breaker
B90-A
B90-B
B90-C
B90-A
B90-B
B90-C
B90-Logic
GE Digital Energy Multilin
Page 74 2015-01-15 Rev. 2 JCT
B90 Applications for Large Busbars Continued
1 2 11
ZONE 1
12 13 22
23 24ZONE 2
Single Bus Single Breaker with Bus Tie
1
2
3
4
21
22
23
24
ZONE 1
ZONE 2
Double Bus Double Breaker
B90-A
B90-B
B90-C
B90-A
B90-B
B90-C
GE Digital Energy Multilin
Page 75 2015-01-15 Rev. 2 JCT
Applying the B30 or B90 for Busbar Protection
Basic Topics
Configure physical CT Inputs
Configure Bus Zone and Dynamic Bus Replica
Calculating Bus Differential Element settings
Advanced Topics
Isolator Monitoring
More on Dynamic Bus Replica Blind Spots & End Fault Protection
Differential Zone CT Trouble
Additional Security for the Bus Differential Zone
B90 Application Example
GE Digital Energy Multilin
Page 76 2015-01-15 Rev. 2 JCT
Configuring CT Inputs
For each connected CT circuit enter Primary rating and select Secondary rating.
For the B30, each 3-phase bank of CT inputs must be assigned to a Signal Source (SRC1 through SRC6) which are then assigned to the
Bus Zone and Dynamic Bus Replica
For the B90, the CT channels are assigned directly to the Bus Zone and Dynamic Bus Replica (no Signal Sources)
Both the B30 and B90 define 1 p.u. as the maximum primary current of all of the CTs connected in the given Bus Zone
GE Digital Energy Multilin
Page 77 2015-01-15 Rev. 2 JCT
B90 Per-Unit Current Definition - Example
DSP Channel Primary Secondary Zone
CT-1 F1 3200 A 1 A 1
CT-2 F2 2400 A 5 A 1
CT-3 F3 1200 A 1 A 1
CT-4 F4 3200 A 1 A 2
CT-5 F5 1200 A 5 A 2
CT-6 F6 5000 A 5 A 2
For Zone 1, 1 p.u. = 3200 Apri
For Zone 2, 1 p.u. = 5000 A pri
GE Digital Energy Multilin
Page 78 2015-01-15 Rev. 2 JCT
Configuration of Bus Zone (Dynamic Bus Replica)
Dynamic Bus Replica associates a status signal with each current in the Bus Differential Zone
Status signal can be any FlexLogic operand
Status signals can be developed in FlexLogic to provide additional checks or security as required
Status signal can be set to ON if current is always in the bus zone or OFF if current is never in the bus zone
For the B30, each Signal Source (SRC1 SRC6) must be assigned a status signal to be included in the three-phase Bus Zone
For the B90, the CT channels are assigned status inputs directly in the respective Bus Zone(s) and the CT direction must also be
configured for all current inputs in each bus zone
In or Out, depending on CT polarity
GE Digital Energy Multilin
Page 79 2015-01-15 Rev. 2 JCT
differ
ent
ial
restraining
LOW
SLOPE
OPERATE
BLOCK
IR
|ID|
HIGH
SLOPE
LO
W B
PN
T
HIG
H B
PN
T
PICKUP
Bus Differential Characteristic Settings
6 key 87B settings to ensure correct differential characteristic for dependable and secure operation
GE Digital Energy Multilin
Page 80 2015-01-15 Rev. 2 JCT
Calculating Bus Differential Settings Pickup
Pickup
Defines the minimum differential current required for operation of the Bus Zone Differential element
Must be set above maximum leakage current not zoned off in the bus differential zone (VTs for example)
May also be set above maximum load conditions for added security in case of CT trouble, but better alternatives exist
Range: 0.050 p.u. to 2.000 p.u. in 0.001 p.u. increments
GE Digital Energy Multilin
Page 81 2015-01-15 Rev. 2 JCT
Calculating Bus Differential Settings Low Slope
Low Slope
Defines the percent bias for the restraint currents from IREST=0 to IREST=Low Breakpoint
Setting determines the sensitivity of the differential element for low-current internal faults
Must be set above maximum error introduced by the CTs in their normal linear operating mode
Range: 15% to 100% in 1%. increments
GE Digital Energy Multilin
Page 82 2015-01-15 Rev. 2 JCT
Calculating Bus Differential Settings Low Breakpoint
Low Breakpoint
Defines the upper limit to restraint currents that will be biased according to the Low Slope setting
Should be set to be above maximum load but not more than maximum current where CTs still operate linearly (including residual flux)
Assumption is that CTs will be operating linearly (no significant saturation up to 80% residual flux) up to the Low Breakpoint setting
Range: 1.00 to 4.00 p.u. in 0.01 p.u. increments
GE Digital Energy Multilin
Page 83 2015-01-15 Rev. 2 JCT
Calculating Bus Differential Settings High Breakpoint
High Break Point
Defines the minimum restraint currents that will be biased according to the High Slope setting
Should be set to be below the minimum current where the weakest CT will saturate with no residual flux
Assumption is that CTs will be operating linearly (no significant saturation effects up to 80% residual flux) up to Low Breakpoint setting
Range: 4.00 to 30.00 p.u. in 0.01 p.u. increments
GE Digital Energy Multilin
Page 84 2015-01-15 Rev. 2 JCT
Calculating Bus Differential Settings High Slope
High Slope
Defines the percent bias for restraint currents larger than high breakpoint
Setting determines stability of differential element for high current external faults
Should be high enough to tolerate spurious differential current during saturation of CTs on heavy external faults
Setting can be relaxed in favor of sensitivity and speed as CT saturation and directional principle is used for security
Range: 50% to 100% in 1% increments
GE Digital Energy Multilin
Page 85 2015-01-15 Rev. 2 JCT
Calculating Bus Differential Settings Unrestrained
Unrestrained
Defines the minimum differential current for unrestrained operation
Should be set to be above the maximum differential current under worst case CT saturation
Range: 2.00 to 99.99 p.u. in 0.01 p.u. increments
Can be effectively disabled by setting to 99.99 p.u.
Unrestrained Differential
GE Digital Energy Multilin
Page 86 2015-01-15 Rev. 2 JCT
Summing External Currents Not Recommended If additional circuit needed
Relay becomes combination of restrained and unrestrained elements
In order to parallel CTs:
CT performance must be closely matched
Any errors will appear as differential currents
Associated feeders must be radial
No backfeeds possible
Pickup setting must be raised to accommodate any errors
Rather change to B90 or B95Plus
CT-1
CT-2
CT-3
CT-4
I 3 =
0
I 2 =
0
I 1 =
Err
or
IDIFF
= Error
IREST
= Error
Maloperation if
Error > PICKUP
GE Digital Energy Multilin
Page 87 2015-01-15 Rev. 2 JCT
Advanced Topics
GE Digital Energy Multilin
Page 88 2015-01-15 Rev. 2 JCT
Advanced Topics
Isolators and Isolator Monitoring
More on Dynamic Bus Replicas
Blind Spots
End Fault Protection
Differential Zone CT Trouble
Additional Security for the Bus Differential Zone
External Check Zone
Undervoltage Supervision
Overcurrent Supervision
B90 Application Examples
B95Plus Application Examples
GE Digital Energy Multilin
Page 89 2015-01-15 Rev. 2 JCT
Isolators
Reliable Isolator Closed signals are needed for the Dynamic Bus Replica
In simple applications, a single normally closed contact may be sufficient
For maximum security:
Both N.O. and N.C. contacts should be used
Isolator Alarm should be established and non-valid combinations (open-open, closed-closed) should be sorted out
Switching operations should be inhibited until bus image is recognized with 100% accuracy
Optionally block 87B operation from Isolator Alarm
Each isolator position signal decides:
Whether or not the associated current is to be included in the differential calculations
Whether or not the associated breaker is to be tripped
GE Digital Energy Multilin
Page 90 2015-01-15 Rev. 2 JCT
Isolator Typical Open/Closed Connections
GE Digital Energy Multilin
Page 91 2015-01-15 Rev. 2 JCT
Full-Featured Isolator Monitoring
Isolator Open Aux.
Contact
Isolator Closed Aux.
Contact
Isolator Position
Isolator Alarm Block Switching
Off On CLOSED No No
Off Off LAST VALID After time delay until reset
Until isolator position valid On On CLOSED
On Off OPEN No No
For the B30, this needs to be implemented using FlexLogic
For the B90 & B95Plus, there are 48 dedicated Isolator Position monitoring elements
GE Digital Energy Multilin
Page 92 2015-01-15 Rev. 2 JCT
Switching An Isolator Closing Sequence
GE Digital Energy Multilin
Page 93 2015-01-15 Rev. 2 JCT
Dynamic Bus Replica Changing the Bus Zone
TB Z1 Z2
Bus Tie Breaker with Two CTs
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)
GE Digital Energy Multilin
Page 94 2015-01-15 Rev. 2 JCT
Dynamic Bus Replica Changing the Bus Zone
Bus Tie Breaker with Single CTs
TB Z1 Z2
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
GE Digital Energy Multilin
Page 95 2015-01-15 Rev. 2 JCT
Dynamic Bus Replica Changing the Bus Zone
Sequence of events:
1. Z1 trips and the TB gets opened
2. After a time delay the current from the CT shall be removed
from Z2 calculations
3. As a result Z2 gets extended up to the opened TB
4. The Fault becomes internal for Z2
5. Z2 trips finally clearing the fault
TB Z1 Z2
expand
GE Digital Energy Multilin
Page 96 2015-01-15 Rev. 2 JCT
Dynamic Bus Replica Changing the Bus Zone
CT
CB
Blind spot for
bus protection
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)
Identical to the Single-CT Tie-Breaker
GE Digital Energy Multilin
Page 97 2015-01-15 Rev. 2 JCT
Dynamic Bus Replica Changing the Bus Zone
CB
CT
Over-trip spot for bus protection
Over-trip spot between the CB and CT when the CB is opened
When the CB opens, the current shall be removed from differential calculations (contracting the differential zone up to the opened CB)
Identical as for the Single-CT Tie-Breaker, but
contra
ct
GE Digital Energy Multilin
Page 98 2015-01-15 Rev. 2 JCT
Dynamic Bus Replica Changing the Bus Zone
but
A blind spot created by contracting the bus differential zone
End Fault Protection required to trip remote end circuit breaker(s)
CB
CT
Blind spot for
bus protection
GE Digital Energy Multilin
Page 99 2015-01-15 Rev. 2 JCT
End Fault Protection (EFP)
Instantaneous overcurrent element enabled when the associated CB is open to cover the blind spot between the CB and line-side CT
Pickup delay should be long enough to ride-through the ramp down of current interruption (1.3 cycles maximum)
EFP inhibited from circuit breaker manual close command
For the B30, the End Fault Protections need to be implemented using FlexLogic
For the B90 & B95Plus, there are 24 dedicated End Fault Protection elements
GE Digital Energy Multilin
Page 100 2015-01-15 Rev. 2 JCT
Differential Zone CT Trouble
Each Bus Differential Zone (2 for the B30, 4 (6) for the B90 and B95Plus) has a dedicated CT Trouble Monitor
Definite Time Delay overcurrent element operating on the zone differential current, based on the configured Dynamic Bus Replica
Three strategies to deal with CT problems:
1. Trip the bus zone as the problem with a CT will likely evolve into a bus fault anyway
2. Do not trip the bus, raise an alarm and try to correct the problem manually
3. Switch to setting group with 87B minimum pickup setting above the maximum load current.
GE Digital Energy Multilin
Page 101 2015-01-15 Rev. 2 JCT
Strategies 2 and 3 can be accomplished by: Using undervoltage supervision to ride through the period from the
beginning of the problem with a CT until declaring a CT trouble condition
Using an external check zone to supervise the 87B function
Using CT Trouble to prevent the Bus Differential tripping (2)
Using setting groups to increase the pickup value for the 87B function (3)
DO NOT use the Bus Differential element BLOCK input: The element traces trajectory of the differential-restraining point for
CT saturation detection and therefore must not be turned on and off
dynamically
Supervise the trip output operand of the 87B in FlexLogic instead
Differential Zone CT Trouble
GE Digital Energy Multilin
Page 102 2015-01-15 Rev. 2 JCT
Differential Zone CT Trouble Strategy #2 Example
CT Trouble operand is used to rise an alarm
The 87B trip is inhibited after CT Trouble element operates
The relay may misoperate if an external fault occurs after CT trouble but before the CT trouble condition is declared (double-contingency)
87B operates
Undervoltage condition
CT OK
GE Digital Energy Multilin
Page 103 2015-01-15 Rev. 2 JCT
Additional Security for The Bus Differential Zone
No matter how high the reliability, any relay may fail. For bus applications, any MTBF will never be high enough
Consider securing the application against reasonable contingencies
CT problems, AC wiring problem
Problems with aux. switches for breakers, isolators
DC wiring problems involving the Dynamic Bus Replica
Failure of relay hardware (single current input channel, single digital input)
Security above and beyond inherent security mechanisms in the B30/B90/B95Plus
CT Saturation Detector
Directional (Phase) Comparison
Isolator monitoring
GE Digital Energy Multilin
Page 104 2015-01-15 Rev. 2 JCT
External Check Zone
Principle:
Develop an independent copy of the differential current for the entire bus regardless of dynamic zones for
individual bus sections
Use the check zone to supervise the tripping zone(-s)
Use independent CTs / CT cores if possible to guard against CT and wiring problems
Use independent relay current inputs to guard against relay problems
Alarm on spurious differential
Guards against:
CT problems
AC wiring problems
Problems with aux switches for breakers and disconnectors
DC wiring problems for dynamic bus replica
Failures of current inputs
GE Digital Energy Multilin
Page 105 2015-01-15 Rev. 2 JCT
With only six 3-phase inputs the B30 handles up to 2 zones of protection
Actual (tripping) zone shall be configured to reflect dynamic image of the bus
External check zone can be configured in some circumstances as an unrestrained zone that (ideally) uses separate CTs or CT cores
An IOC function may be configured if needed to operate on the externally summated currents (From different IED)
For external zone identical CT ratios or matching transformers are required
Make use of three ground CT inputs (IG) and Ground IOC or unused 3-phase bank & Phase IOC elements to provide check zone
Application of the External Check Zone to the B30
GE Digital Energy Multilin
Page 106 2015-01-15 Rev. 2 JCT
87B phase A supervised by IOC1
phase A; the IOC responds to the
externally formed differential
current
Three-phase trip command
Application of the External Check Zone to the B30
GE Digital Energy Multilin
Page 107 2015-01-15 Rev. 2 JCT
Application of the External Check Zone to the B90
Version 1
Use two different CTs / CT cores
Place the supervising zone in a different chassis
Strong security bias, practically a 2-out-of-2
independent relay scheme
Use fail-safe output to substitute for the permission
if the supervising relay fails / is taken out of service
...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b ...
DSP, SSot S
S1c S1b S2c S2b S8c S8b
B1a B2b
Critifal Failure
b ca b
Digital Input
a b
Digital Input
Phase A
BUS DIF 1
(TRIPPING
PHASE A)
BUS DIF 4
(SUPERVISING
PHASE C)
b c
OR
B90-A
AN
D
TRIP A
to B90-Cto B90-C
from
phase-C CT
...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b ...
DSP, SSot S
S1c S1b S2c S2b S8c S8b
B1a B2b
Critifal Failure
b ca b
Digital Input
a b
Digital Input
Phase B
BUS DIF 1
(TRIPPING
PHASE B)
BUS DIF 4
(SUPERVISING
PHASE A)
b c
OR
B90-B
AN
D
TRIP B
to B90-C
from B90-C
GE Digital Energy Multilin
Page 108 2015-01-15 Rev. 2 JCT
Application of the External Check Zone to the B90
Version 2
Use two different CTs / CT cores
Place the supervising zone in the same chassis, different DSP module
Strong security bias, almost 2-out-of-2 independent relay scheme
Simpler panel wiring compared with version 1 (No inter chassis wiring needed)
...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b ...
DSP, SSot S
S1c S1b S2c S2b S8c S8b
b c
Phase A
BUS DIF 1
(TRIPPING
PHASE A)
BUS DIF 4
(SUPERVISING
PHASE A)
B90-A
AND
TR
IP A
GE Digital Energy Multilin
Page 109 2015-01-15 Rev. 2 JCT
Application of the External Check Zone to the B90
Version 3
Use a single CT (simpler wiring)
Place the supervising zone in a different chassis
Guards against relay problems and bus replica
problems
Use fail-safe output to substitute for the permission
if the supervising relay fails / is taken out of service
...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b ...
DSP, SSot S
S1c S1b S2c S2b S8c S8b
B1a B2b
Critifal Failure
b ca b
Digital Input
a b
Digital Input
Phase A
BUS DIF 1
(TRIPPING
PHASE A)
BUS DIF 4
(SUPERVISING
PHASE C)
b c
OR
B90-A
AN
D
TRIP A
to B90-Cto B90-C
from
phase-C CT
...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b ...
DSP, SSot S
S1c S1b S2c S2b S8c S8b
B1a B2b
Critifal Failure
b ca b
Digital Input
a b
Digital Input
Phase B
BUS DIF 1
(TRIPPING
PHASE B)
BUS DIF 4
(SUPERVISING
PHASE A)
b c
OR
B90-B
AN
D
TRIP B
from B90-C
to B90-C
GE Digital Energy Multilin
Page 110 2015-01-15 Rev. 2 JCT
Application of the External Check Zone to the B90
Version 4
Use a single CT
Place the supervising zone in the same chassis, different DSP module
Guards against relay problems and bus replica problems
No inter chassis wiring needed
...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b ...
DSP, SSot S
S1c S1b S2c S2b S8c S8b
b c
Phase A
BUS DIF 1
(TRIPPING
PHASE A)
BUS DIF 4
(SUPERVISING
PHASE A)
B90-A
AND
TR
IP A
GE Digital Energy Multilin
Page 111 2015-01-15 Rev. 2 JCT
Undervoltage Supervision
Principle:
Supervise all differential trips with undervoltage
Set high (0.85-0.90pu) for speed and sensitivity
Need 3 UV elements per bus per phase (undervoltage functions AG, AB, CA
supervise differential trip for phase A)
Alarm on spurious differential
Guards against:
CT problems
AC wiring problems
Problems with aux switches for breakers and disconnectors
DC wiring problems for dynamic bus replica
Failures of current inputs
GE Digital Energy Multilin
Page 112 2015-01-15 Rev. 2 JCT
Application of Undervoltage Supervision to the B90
Version 1
Place the supervising voltage inputs in a different chassis
Guards against relay problems and bus replica problems
Does not need any extra ac current wiring
Use fail-safe output to substitute for the permission
if the supervising relay fails / is taken out of service
S7a S7cS6a S6c...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b
DSP, SSot S
... S8a S8c
B1a B2b
Critifal Failure
b ca b
Digital Input
a b
Digital Input
Phase A
BUS DIF 1
(TRIPPING
PHASE A)UV-1
b c
OR
B90-A
AN
D
TRIP A
to B90-Cto B90-C
...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b
DSP, SSot S
B1a B2b
Critifal Failure
b ca b
Digital Input
a b
Digital Input
Phase B
BUS DIF 1
(TRIPPING
PHASE B)O
R
AN
D
TRIP B
from B90-C
VCAVBCVCG
UV-2 UV-3
OR
S7a S7cS6a S6c... S8a S8c
UV-1
b c
VCAVABVAG
UV-2
OR
B90-B
UV-3
GE Digital Energy Multilin
Page 113 2015-01-15 Rev. 2 JCT
Application of Undervoltage Supervision to the B90
Version 2
Place the supervising voltage inputs in the same chassis
Guards against relay problems and bus replica problems
Does not need any extra ac current wiring
No inter chassis wiring needed
S7a S7cS6a S6c...
DSP, Slot F
F1c F1b F2c F2b F8c F8b ...
DSP, Slot L
L1c L1b L2c L2b L8c L8b
DSP, SSot S
... S8a S8c
Phase A
BUS DIF 1
(TRIPPING
PHASE A)UV-1
VCAVABVAG
UV-2 UV-3
OR
b c
AND
TR
IP A
B90-A
GE Digital Energy Multilin
Page 114 2015-01-15 Rev. 2 JCT
Overcurrent Supervision
Principle:
Supervise trips to breakers with OC condition set above maximum load
Loads will not get tripped; facilitates bus transfer applications
With a single CT / wiring / relay input problem, only up to one breaker will get tripped, not the entire bus
Danger that very weak sources feeding a bus fault will not get tripped, solution possible via logic
Guards against:
CT problems
AC wiring problems
Problems with aux switches for breakers and disconnectors
DC wiring problems for dynamic bus replica
Failures of current inputs
Typically, no trip will occur on CT and wiring problems
A single CB may get tripped on specific relay problems (sees spuriously high current)
GE Digital Energy Multilin
Page 115 2015-01-15 Rev. 2 JCT
B90/B95Plus Application Examples
GE Digital Energy Multilin
Page 116 2015-01-15 Rev. 2 JCT
B90 Example Reconfigurable Bus
Double bus, single breaker with bus-tie
10 feeders with single CT
Circuit breaker bypass switches per feeder CB
Current inclusion in bus zone depends on isolator switch position (ISO x)
CB1-2
L8
L7
ISO
1
ISO
2
CB1
F1IS
O3
CB2
F2
CB3
F3
CB4
F4
CB5
F5
CB6
F6
CB7
F7
CB8
F8
CB9
L1
CB10
L2
IOS
4
ISO
5
ISO
6
ISO
7
ISO
8
ISO
9
ISO
10
ISO
11
ISO
12
ISO
13
ISO
14
ISO
15
ISO
16
ISO
17
ISO
18
ISO
19
ISO
20
ISO
21
ISO
22
ISO
23
ISO
24
ISO
25
ISO
26
ISO
27
ISO
28
ISO
29
ISO
30
ISO
31
ISO
32
ZONE 1=BUS1
ZONE 2=BUS2
ZONE 3=CHECK ZONE
GE Digital Energy Multilin
Page 117 2015-01-15 Rev. 2 JCT
B90 Example Architecture
Breaker Failure
inputs and outputs
Phase A AC signals
and trip contacts
Phase B AC signals and trip contacts
Phase C AC signals
and trip contacts
Digital Inputs for
isolators and
breakers monitoring
Tx Rx
Rx Tx
Dir
ect
I/O
Rin
g (C
h. 1
) Direct I/O
Rin
g (C
h. 2
)
GE Digital Energy Multilin
Page 118 2015-01-15 Rev. 2 JCT
INCLUSION OF FEEDER CTs INTO BUS 1(ZONE 1), OR BUS 2(ZONE 2) PROTECTION
B90 Example Dynamic Bus Replica Logic
GE Digital Energy Multilin
Page 119 2015-01-15 Rev. 2 JCT
DIFFERENTIAL ZONE 2 (BUS 2)
Differential current: Id = F2 + F4 + F5 +F6 +F7 +L1 + L7
Restraint current: Ir = max(F2, F4, F5, F6, F7, L1, L7)
DIFFERENTIAL ZONE 3 (CHECK ZONE = BUS 1 + BUS 2)
Differential current: Id = F1 +F2 + F3 +F4 +F5 +F6 +F7 + F8 + L1 +L2 +
+ (L7 OR L8) WHEN FEEDER CT BY-PASSED
Restraint current: Ir = max(F1, F2, F3, F4, F5, F6, F7, F8, L1, L2,
(L7 OR L8) WHEN FEEDER CT BY-PASSED)
DIFFERENTIAL ZONE 1 (BUS 1)
Differential current: Id = F1 + F3 + F8 + L2 + L8
Restraint current: Ir = max(F1, F3, F8, L2, L8)
B90 Bus Zone Definitions (Dynamic Bus Replica)
GE Digital Energy Multilin
Page 120 2015-01-15 Rev. 2 JCT
B90-1 A PHASE
B90-2 B PHASE
B90-3 C PHASE
B90-5 BKR FAIL
B90-4 STATUS
Direct outputs on IED4
Direct inputs on IED1, 2, and 3
Fiber Optic
channels
Differential zones
configuration on
IED1, 2, and 3
ZONE 1 ZONE 2 ZONE 3
B90 Direct I/O Communications Configuration
Isolators and breakers
positions
GE Digital Energy Multilin
Page 121 2015-01-15 Rev. 2 JCT
B90 Example AG Fault on Bus 1
CB1-2
L8
L7
ISO
1
ISO
2
CB1
F1IS
O3
CB2
F2
CB3
F3
CB4
F4
CB5
F5
CB6
F6
CB7
F7
CB8
F8
CB9
L1
CB10
L2
IOS
4
ISO
5
ISO
6
ISO
7
ISO
8
ISO
9
ISO
10
ISO
11
ISO
12
ISO
13
ISO
14
ISO
15
ISO
16
ISO
17
ISO
18
ISO
19
ISO
20
ISO
21
ISO
22
ISO
23
ISO
24
ISO
25
ISO
26
ISO
27
ISO
28
ISO
29
ISO
30
ISO
31
ISO
32
ZONE 1=BUS1
ZONE 2=BUS2
ZONE 3=CHECK ZONE
GE Digital Energy Multilin
Page 122 2015-01-15 Rev. 2 JCT
B90 Example AG Fault on Bus 1 Trip with BF Logic
AG Undervoltage
AB Undervoltage
CA Undervoltage
BUS1 OP
BUS3 BIASED PKP
Trip 87B Zone1
BF Trip Zone1
80msTIMER
Trip Zone1 87B or BF
AG Undervoltage
AG Undervoltage
AG Undervoltage
BUS2 OP
BUS3 BIASED PKP
Trip 87B Zone2
BF Trip Zone2
80msTIMER
Trip Zone2 87B or BF
*
*
* Denotes a binary signal received from an external B90 via communications (Direct I/O,
GOOSE/GSSE)
GE Digital Energy Multilin
Page 123 2015-01-15 Rev. 2 JCT
B90 Example AG Fault on Bus 1 Trip Logic
Trip Zone1 87B or BF
Trip Zone2 87B or BF
ISO 31 ON
ISO32 ON
TRIP CB1-2
F1 in Zone1
TRIP CB1F1 in Zone2
F2 in Zone1
TRIP CB2F2 in Zone2
F3 in Zone1
TRIP CB3F3 in Zone2
F4 in Zone1
TRIP CB4F4 in Zone2
F5 in Zone1
TRIP CB5F5 in Zone2
F6 in Zone1
TRIP CB6F6 in Zone2
F7 in Zone1
TRIP CB7F7 in Zone2
F8 in Zone1
TRIP CB8F8 in Zone2
L1 in Zone1
TRIP CB9L1 in Zone2
L2 in Zone1
TRIP CB10L2 in Zone2
*
*
*
*
*
*
*
*
*
*
*
* *
*
*
*
*
*
*
*
*
*
GE Digital Energy Multilin
Page 124 2015-01-15 Rev. 2 JCT
B95Plus Large Double Bus
Two Double Buses tied together
20 Feeders
4 Bus Couplers
Requirements:
Differential Protection
Isolator Position Monitoring
Supervision for Isolator position monitoring failure
GE Digital Energy Multilin
Page 125 2015-01-15 Rev. 2 JCT
One Solution: (1) B95Plus
B32 B31 B27 B25 B23 B21
B28 B26 B24 B22
B20
B19
B20
B12
B10
B8
B6
B4
B2
B3
B5
B7
B9
B19
One Solution
v One B95Plus
v 14 Bricks (10 shared between feeders, 4 for bus couplers)
v 4 bus zonesv Check zone possible
GE Digital Energy Multilin
Page 126 2015-01-15 Rev. 2 JCT
B95Plus Shared Brick
3 currents
B28 B26
3 currents
2 status2 control
2 status2 control
2 status2 status
Brick wired for both circuits
v Source currents (3)v Breaker control (2 outputs)v Breaker status (2 inputs)v Isolator status (2 inputs each)
One circuit
GE Digital Energy Multilin
Page 127 2015-01-15 Rev. 2 JCT
Better solution: (2) B95Plus Systems
B32 B31 B27 B25 B23 B21
B28 B26 B24 B22
B20
B19
B20
B12
B10
B8
B6
B4
B2
B3
B5
B7
B9
B19
Better Solution
v Two B95Plus
v 24 Bricks v 2 bus zones per B95Plus
v Check zone not possible
GE Digital Energy Multilin
Page 128 2015-01-15 Rev. 2 JCT
Breaker-and-a-half
GE Digital Energy Multilin
Page 129 2015-01-15 Rev. 2 JCT
Conclusions
GE Digital Energy Multilin
Page 130 2015-01-15 Rev. 2 JCT
Conclusions
B30
For smaller busbars (up to 6 feeders, 2 Zones)
Single chassis providing three-phase bus differential protection, logic and I/O capabilities
Isolator monitoring may be done in FlexLogic if required
End Fault Protection may be provided using FlexLogic if required
Additional security can be provided (fewer feeders in zone)
Inter-relay communications supported for additional I/O
B90 and B95Plus
For large, complex busbars (up to 24 feeders, 6 Zones)
(B90)Multiple chassis for single-phase bus differential, plus extra IEDs for dynamic bus replica, breaker fail
Internal full-feature isolator monitoring provided
24 End Fault Protection elements provided (B90 and B95Plus)
Additional security can be provided (fewer feeders in zone)
Inter-relay communications supported for additional I/O
GE Digital Energy Multilin
Page 131 2015-01-15 Rev. 2 JCT
Conclusions
B30 is limited in scope to small busbars, therefore application is fairly simple and straightforward
B90 designed to be applied to large complex busbars, therefore application can be quite complicated:
Multiple B90s:
Protection Algorithm processing
Dynamic Bus Replica logic
Isolator monitoring
Breaker Failure
Inter-relay Communication schemes for I/O transfer, inter-tripping
GE Multilin can provide a complete engineered B90 System Solution, based on specific customer application & requirements
GE Digital Energy Multilin
Page 132 2015-01-15 Rev. 2 JCT
Conclusions
B30, B90 and B95Plus provide secure, high performance bus differential protection for reconfigurable busbars using the same
proven algorithms
Both B30 and B90 are members of the Universal Relay (UR) family, with common configuration and management tools for all relays:
EnerVista UR Setup: Universal configuration tool
EnerVista ViewPoint: software suite for all GE Multilin IEDs
Launchpad: Device Setup & Document Management
Engineer: Advanced Logic Design & Monitoring (Optional)
Maintenance: Troubleshooting & Reporting Tools (Optional)
Monitoring: Monitoring & Data Recording for Small Systems (Optional)
www.GEMultilin.com
GE Digital Energy Multilin
Page 133 2015-01-15 Rev. 2 JCT
Conclusion: B95Plus as Centralized DFR
DFR functionality includes an Event Recorder and Transient Recorder
Event Recorder
8,192 events on Main Card
8,192 events on each process card
Events viewable on HMI window or retrievable through setup software
Transient Recorder
Up to 50 records, up to 128 samples / cycle
Re-trigger capability to extend recording as additional triggers are asserted
128 digital channels and triggers for Main card, each process card
Captures all bus source currents, voltage sources, differential and restraint currents
All data reviewable through EnerVista B95Plus Setup Software
GE Digital Energy Multilin
Page 134 2015-01-15 Rev. 2 JCT
Q & A