Download pdf - Bus Protection Seminar Jun2015

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


Page 3 2015-01-15 Rev. 2 JCT

Presentation Outline

GE’s Multilin Bus Protection Portfolio

B30, B90 & B95Plus Application Considerations

Advanced Application Topics

B90 & B95Plus Application Examples


Page 4 2015-01-15 Rev. 2 JCT

Introduction to Bus Protection


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…


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…


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


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


Page 9 2015-01-15 Rev. 2 JCT

Bus Arrangements and Components


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


Page 11 2015-01-15 Rev. 2 JCT

Typical Industrial Single Bus


Page 12 2015-01-15 Rev. 2 JCT

Typical Industrial Double Bus


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


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


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


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


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


Page 18 2014-09-15 Rev. 1 JCT

Protection Techniques


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 Kirchoff’s Law for Currents:

‘The sum of all currents entering a node must equal zero.’

The only variation is on how this is implemented.


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


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


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


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


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


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)


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.


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)


Page 28 2015-01-15 Rev. 2 JCT

CT Saturation


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


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


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


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)


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


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


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 ratio’s and classes can be used

• CT’s 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 ratio’s, class required (Same B/H &

knee-point voltage) (Cost)

• CT’s 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


Page 37 2015-01-15 Rev. 2 JCT

GE’s Multilin Bus Protection Portfolio


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


Page 39 2015-01-15 Rev. 2 JCT

Electro-mechanical Work-horse:

• Fast: typical operating time of 16 – 30 mS • Phase packaged (3 required) • 100’s of thousands in service • Still available (expensive) • Aging fleet will need replacing due to capacitor failures

High Impedance Bus Protection (PVD)


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)


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)


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.


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.


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


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)


Page 46 2015-01-15 Rev. 2 JCT

B30 Bus Differential Protection - Wiring


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)


Page 48 2015-01-15 Rev. 2 JCT

MAIN PROTECTION

Four Bus Differential zones:

• Restrained (87B)

• Unrestrained/instantaneous (50/87)


VOLTAGE SUPERVISION


BACKUP

Phase TOC (51) - per feeder

Phase IOCs (50) - per feeder

OTHER

Breaker Failure per breaker (50BF)

CT Trouble (50/74)

B90 Protection Features


Page 49 2015-01-15 Rev. 2 JCT



• 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


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



• Different CT Ratio Capability for Each Circuit • Largest CT Primary is Base in Relay


Page 51 2015-01-15 Rev. 2 JCT

B90 Bus Differential Protection - Wiring


Page 52 2015-01-15 Rev. 2 JCT

MAIN PROTECTION

Uses Merging Units (BRICKs)

Six Bus Differential zones: • Restrained (87B)

• Unrestrained/instantaneous (50/87)


VOLTAGE SUPERVISION


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


Page 53 2015-01-15 Rev. 2 JCT

B95Plus System Architecture


Page 54 2015-01-15 Rev. 2 JCT

B95Plus Bus Differential Protection - Wiring


Page 55 2015-01-15 Rev. 2 JCT



Page 56 2015-01-15 Rev. 2 JCT


Configuration of Bus Differential (87B)


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.


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


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


Page 61 2015-01-15 Rev. 2 JCT

Bus Differential Block Diagram


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


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.


Page 64 2015-01-15 Rev. 2 JCT

Bus Differential Adaptive Approach diffe

ren

tial

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


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


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


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


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


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


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


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


Page 72 2015-01-15 Rev. 2 JCT

B30, B90 & B95Plus Application Considerations


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


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


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


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


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


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


Page 79 2015-01-15 Rev. 2 JCT

diff

ere

ntia

l

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


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


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


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


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



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


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


– Can be effectively disabled by setting to 99.99 p.u.

Unrestrained Differential


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


Page 87 2015-01-15 Rev. 2 JCT

Advanced Topics


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


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


Page 90 2015-01-15 Rev. 2 JCT

Isolator – Typical Open/Closed Connections


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


Page 92 2015-01-15 Rev. 2 JCT

Switching An Isolator – Closing Sequence


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)


Page 94 2015-01-15 Rev. 2 JCT


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


Page 95 2015-01-15 Rev. 2 JCT


• 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


Page 96 2015-01-15 Rev. 2 JCT


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


Page 97 2015-01-15 Rev. 2 JCT


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


Page 98 2015-01-15 Rev. 2 JCT


• 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


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


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.


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


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


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


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


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


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



Page 107 2015-01-15 Rev. 2 JCT


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


DSP, Slot L


DSP, SSot S


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


Page 108 2015-01-15 Rev. 2 JCT


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


DSP, Slot L


DSP, SSot S


b c

Phase A

BUS DIF 1

(TRIPPING

PHASE A)

BUS DIF 4

(SUPERVISING

PHASE A)

B90-A

AND

TR

IP A


Page 109 2015-01-15 Rev. 2 JCT


Version 3

• Use a single CT (simpler

wiring)

• Place the supervising zone in

a different chassis

• Guards against relay

problems and bus replica

problems




...

DSP, Slot F


DSP, Slot L


DSP, SSot S


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


DSP, Slot L


DSP, SSot S


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


Page 110 2015-01-15 Rev. 2 JCT


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


DSP, Slot L


DSP, SSot S


b c

Phase A

BUS DIF 1

(TRIPPING

PHASE A)

BUS DIF 4

(SUPERVISING

PHASE A)

B90-A

AND

TR

IP A


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



• DC wiring problems for dynamic bus

replica



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




S7a S7cS6a S6c...

DSP, Slot F


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


DSP, Slot L


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


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


DSP, Slot L


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


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



• DC wiring problems for dynamic bus replica


• Typically, no trip will occur on CT and wiring problems

• A single CB may get tripped on specific relay problems (sees spuriously high current)


Page 115 2015-01-15 Rev. 2 JCT

B90/B95Plus Application Examples


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

F1ISO

3

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


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

) Dire

ct I/O R

ing

(Ch

. 2)


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


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)


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


Page 121 2015-01-15 Rev. 2 JCT

B90 Example – AG Fault on Bus 1

CB1-2

L8

L7

ISO

1

ISO

2

CB1

F1ISO

3

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


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


*

*

* Denotes a binary signal received from an external B90 via communications (Direct I/O,

GOOSE/GSSE)


Page 123 2015-01-15 Rev. 2 JCT

B90 Example – AG Fault on Bus 1 Trip Logic



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

*

*

*

*

*

*

*

*

*

*

*

* *

*

*

*

*

*

*

*

*

*


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


Page 125 2015-01-15 Rev. 2 JCT

One Solution: (1) B95Plus

B32 B31 B27 B25 B23 B21

B28 B26 B24 B22

B2

0B

19

B20

B1

2B

10

B8

B6

B4

B2

B3

B5

B7

B9

B1

9

One Solution

v One B95Plus

v 14 Bricks (10 shared

between feeders, 4 for bus couplers)

v 4 bus zones

v Check zone possible


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


Page 127 2015-01-15 Rev. 2 JCT

Better solution: (2) B95Plus Systems

B32 B31 B27 B25 B23 B21

B28 B26 B24 B22

B2

0B

19

B20

B1

2B

10

B8

B6

B4

B2

B3

B5

B7

B9

B1

9

Better Solution

v Two B95Plus

v 24 Bricks

v 2 bus zones per B95Plus

v Check zone not possible


Page 128 2015-01-15 Rev. 2 JCT

Breaker-and-a-half


Page 129 2015-01-15 Rev. 2 JCT

Conclusions


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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


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


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

http://www.gemultilin.com/


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


Page 134 2015-01-15 Rev. 2 JCT

Q & A