Dist Relay Power Point

8/7/2019 Dist Relay Power Point

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NERC

System Protection and Control

Task Force

Presented to the Edison ElectricInstitute

Minneapolis, MNOctober 11, 2004



2

Outline

Distance Relay Applications

Zone 3 ± Remote Backup

Other Remote Backup Methods

Blackout Recommendations SPCTF Clarification of Ratings

SPCTF Recommendations to NERC PC

SPCTF Exception Criteria

Some Possible Mitigation Methods SPCTF Future Activities

Q&A



3


Most common method of protecting for transmission line faults

Calculates distance (impedance) by measuring voltage,current, and the relationship between them at the relaylocation

Can be used with variety of communications systems for

instantaneous protection of entire line

Zone 1 (underreaching, no time delay)

Zone 2 (slightly overreaching, minimal time delay

Zone 3 (significant overreaching, longer time delay) to provideremote backup protection for failure of other protectionsystems

Load carrying capability (relay loadability) is inverselyproportional to distance relay chord length at respective angle



4


Sample Distance Relay Characteristic (Zone 2)

ZR AY

TA

X

R

ZI

.25 ZI

ZR AY

I



5

Zone 3 ± Remote Backup Applications

A Method of Providing Remote Backup

Extended

Zone 2

Time Zone 3

Zone 1

Zone 2

Zone 1

Zone 2

Long Line Short Line Next Line

Normal

Zone 2

Time



6

Other Remote Backup Methods

Direct Transfer Trip

Allow relays to be set shorter

Uses communications systems for remote

backup

Alternative Relay Characteristics

Blinder Characteristics

Lenticular Characteristics Proprietary Load-Tolerant Characteristics (ex.

± Schweitzer Electric Labs Load

Encroachment Characteristic)



7

Remote Backup ± Direct Transfer Trip

Requires additional communicationequipment

Must Be Redundant ± Communication

equipment more prone to fail thanrelaying, breakers, or other equipment

Requires correct operation of protectiverelays on primary protected element

Can not back up for failure of DC batterysystems, or for failure of instrumenttransformers



8

Remote Backup ±Blinder Characteristics

Typically applied to older

electromechanical relays

Separate, supervising

element

Allows full relay reach for fault angles

Provides reasonable arc-

resistance coverage

Can be customized topermit required load flow

Not a good option for

retrofit

30 0 LOAD ANGLE

B

1

B

2

R

jXMTA



9

Remote Backup ± Lenticular Characteristics

Available on solid-state and

some modern

microprocessor relays

Incorporated into relay

design Allows full relay reach for

fault angles

Provides limited arc-

resistance coverage

Can be customized topermit required load flow

Can be a good option for

retrofit if available on

preferred relay

R

TA

L A A L



10

Remote Backup ± SEL Load Encroachment

Example of proprietary load-tolerant characteristics

Can be found only on mostmodern microprocessor relays

Incorporated into relay design

Allows full relay reach for faultangles

Provides good arc-resistancecoverage

Can be customized to permitrequired load flow

Most modern microprocessor relays have some form of load-tolerant characteristic, soproprietary characteristics area good retrofit option

30 0 LOAD ANGLE

R

jXMTA

Load-Encroachment



11

Blackout Recommendations

NERC Recommendation 8a

Approved by NERC Board of Trustees onFebruary 10, 2004

US ± Canada Power System Outage TaskForce Recommendation 21a (Joint TaskForce Recommendation 21a)

Final Report Published on April 4, 2004



12

NERC Recommendation 8a

All transmission owners shall, no later than September 30, 2004,evaluate the zone 3 relay settings on all transmission linesoperating at 230 kV and above for the purpose of verifying thateach zone 3 relay is not set to trip on load under extremeemergency conditions. In each case that a zone 3 relay is set so asto trip on load under extreme conditions, the transmission operator

shall reset, upgrade, replace, or otherwise mitigate the overreachof those relays as soon as possible and on a priority basis, but nolater than December 31, 2005. Upon completing analysis of itsapplication of zone 3 relays, each transmission owner may no later than December 31, 2004 submit justification to NERC for applyingzone 3 relays outside of these recommended parameters. The

Planning Committee shall review such exceptions to ensure theydo not increase the risk of widening a cascading failure of thepower system.

The NERC investigation team recommends that the zone 3 relay, if used, should not operate at or below 150% of the emergency ampererating of a line, assuming a .85 per unit voltage and a line phase angle

of 30 degrees.



13

Joint Task Force Recommendation 21a

NERC Industry is to review zone 3 relays on lines

of 230 kV and higher.

Joint Task Force

Recommends that NERC broaden thereview to include operationally significant

115 kV and 138 kV lines, e.g., lines thatare part of monitored flowgates or interfaces. Transmission owners shouldalso look for zone 2 relays set to operatelike zone 3s.



14

SPCTF Clarification on Ratings

NERC Recommendation 8a footnote

states ³«emergency ampere rating «´

NERC PC Minutes ± March 24 suggests

³«long time summer emergency ampere rating «´

SPCTF Clarification (June 18) ± ³Highest

seasonal ampere circuit rating «´ that³« most closely approximates a 4-hour

rating «´ considering the ³«lowest

ampere rated device in the line«´



15

SPCTF Recommendations

Approved by NERC PC ± July 15, 2004

TPSO ± transmission protection system owner

Current process to address only zone-3 relays

Zone-3 relays defined as remote backup relays

(IEEE C37.113 clause 5.3.7.1)

Inject regions into zone-3 process ± build on

their natural relationships with the TPSO's

TPSOs to respond to regions by dates

established in NERC recommendation 8a



16

1/1/2005 - 12/31/2005

TPSOs mitigate

violations

9/30/2004 -

12/31/2004

TPSOs mitigate

violations

9/30/2004

TPSOs report to Regions

on Zone 3 reviews

12/31/2004

TPSOs Submit to Regions:

- Certification of conformance to loadability

- Violation mitigation (before 12/31/05) plans

- Applications for exceptions

2/10/2004 - 9/30/2004

TPSOs review Zone 3 relays

for conformance

10/31/2004

Regions Report

TPSO completion

of 9/30 review

to SPCTF

1/31/2005

Regions report

TPSO responses

of 12/31/04

to SPCTF

Today2/10/2004

NERC Rec. 8 A

Issued by Board

2/1/2006

Regions report

TPSO responses

of 12/31/05

to SPCTF

12/31/2005

TPSOs Submit to Regions:

- Certification of full conformance

- Implementation dates for outstanding violations

Implementation Timeline for NERC Recommendation 8a

Activities



17

SPCTF Recommendations (Continued)

Regions to assure that all TPSOs have responded

and respond to NERC 1 month later

Establish Two Classes of Exception ± Temporaryand Technical

Temporary Exceptions to Request DelayedSchedule for Workforce or Construction ClearanceIssues

Technical Exceptions to Address Conditions Where

Thermal Limits Are Not the Practical LimitingCondition

SPCTF Developing Technical Exception Criteria

SPCTF to Review All Exception Requests and

Report to PC



18

SPCTF Recommendations (Continued)

Denied Requests Must Be Mitigated in 1 Year

All Other Load-responsive Relays to Be Reviewed

and Addressed on a Schedule to Be Developed by

SPCTF Exceptions to Be Reviewed by Regions

Regions to Identify Critical Lines 115kv and Above

for Inclusion in Review (Joint TF Recommendation21a)



19

SPCTF Exception Criteria

Temporary exceptions

Technical exceptions

Realistic circuit ratings

Achieve minimum acceptable protection

Network topology

Transmission system must be adequately protected,

and distance relaying must also allow for maximum

practical load flow

Distance relaying must not contribute to cascading

outages



20

Temporary Exceptions

Permit delayed implementation because of

workforce issues, construction outage constraints, or

availability of replacement equipment

Not intended to provide for budget relief

TPSOs must do all possible to mitigate with existing

equipment



21

Ratings and Technical Exceptions

NERC Recommendation 8a refers to

circuit thermal ratings

SPCTF Clarified to highest seasonal 4-hour rating of most limiting circuit element

Thermal ratings may not represent

practical circuit capabilities

Technical Exceptions attempt to address

the other practical circuit capabilities



22

Technical Exceptions

Twelve Individual Technical Exception Criteria

Establishes lower margins for shorter-term circuit

ratings (1)

Address other system rating limitations that

present more realistic actual system criteria (6)

Establish ratings based on minimally-adequate

protection (2)

Natural system limitations due to topology (4)



23

Technical Exception #1

Utilize 15-Minute Rating of Transmission Line

³The tripping relay should not operate at or below 115% of the

15-minute winter emergency rating assuming a 0.85 per unit

voltage and a line phase angle of 30 degrees.´

Original blackout recommendations were developed to

permit operator response time

With longer-term ratings, equipment will take longer to load-up

thermally

With a 15-minute rating, system is rated ³closer to the edge´

NERC investigation team advises that 15% of the original margin

is for tolerances, and 35% is to allow longer response time



24

The protective relays need to accommodate

the power transfer capability of a

transmission line

2. Line only Recertify when line is changed

3. Line and breaker interrupter rating

Recertify when breaker is underrated or

changed

4. Line and actual source impedance

Recertify annually

Technical Exceptions #2, 3, and 4



25

Maximum Power Transfer Diagram

R

en ing ecei ing =

¡

=¢

¡

= . P

¡

= . P

L

RS

X

V V P

H sinvv!

The maximum real power that a transmissionline can transfer occurs when the voltage

angle across the line reaches 90º.



26

Maximum Power Transfer Capability

345 kV (2 X 1272 ACSR) Line Loadability

2

6000

0 0 100 1 0 200 2 0 300 3 0 400

Line Length (miles)

A

p p a r e n t P o w e r ( M V A ) & S

t . C l a i r ( M W )

St. Clair Curve MW

St. Clair MVA

S 1.5xW

Ss (Vs=1 =90°)



27

Technical Exception #2, 3 and 4

Exception 2

Uses the line reactance only

1.0 per-unit source voltage at both ends

No additional margin

Exception 3 Uses the line reactance, plus source reactance at each end

reflecting the breaker interrupting ratings



Exception 4

Uses the line reactance, plus actual system source reactances

at both ends





28


Special Considerations for Series-Compensated Lines

Tripping relay should not operate at or below the greater of:

1. 1.15 times the highest emergency ratingof the series capacitor

2 . I total (calculated under Exception 2, 3, or

4 using full line inductive reactance) Assuming

0.85 per unit voltage

line phase angle of 30º



29


Weak Source Systems The tripping relay should not operate at or below

1.414 times 1.15 times I fault assuming a 0.85 per

unit voltage and a line phase angle of 30

degrees where I fault is the maximum end of linethree-phase fault current magnitude

R

T

£

¤

¥

¦

§

I

¦

¦

I

¨

¥

¦

Y

¦

T

©

§

¨

¤

©

¥

T

©

£

T



30

Technical Exceptions #7 and 8

Distance relays must beable to adequatelyprotect line

Exception 7 applies tosimple 2-terminal lines

Exception 8 applies to 3(or more) terminal lines

Establishes anemergency rating basedon relay loadability

Must be recognized byreliability coordinator

RC must take actionwhen load reaches this

rating

.25 !

" "

!

RE#

T

RE $

!

Y

MT

X

R

RE $

!

Y 30

30 0

!

" "

!

RE # T

RE T



31

Technical Exception #7 and #8

Requires That All of Following Conditions Are Met: Most Sensitive Tripping Element Set for e 125%

of Apparent Impedance

MTA Set As Close as Possible to 90 degrees

Calculate a Short-Term Rating I emergency Basedon Relay Setting

I emergency Used in All Planning and Operational

Modeling for the STE Rating

No current or Subsequent Planning Contingency

Analyses Identify Conditions where Recoverable

Flow is > I emergency

Otherwise, must fully mitigate the conditions



32


Generation Remote to LoadFor one line connecting the aggregate generation to thesystem:

The tripping relay should not operate for 1.15 times theI max assuming a 0.85 per unit voltage and a line phase

angle of 30 degreesFor multiple lines connecting the aggregate generation to

the system:

The tripping relay should not operate for 1.15 times I max

assuming a 0.85 per unit voltage and a line phase angleof 30 degrees if all the other lines that connect thegenerator to the system are out of service

I max is defined as:

relayV

MVA I

v

!

3

maxmax



33

Exception 9 ± Generator Connected by Single Line

R

GENERATION BUS

LOAD BUS



34

Exception 9 ± Generator Connected via Multiple Lines

R

GE E TI CE TE

L

R

R

L

L C

L

C

E

T E

E

E



35


Load Remote to GenerationThe tripping relay should not operate for 1.15 times the

maximum current flow as calculated by the TPSO

assuming a 0.85 per unit voltage and a line phase

angle of 30 degrees.%

E&

E ' ( TIO&

) E&

TE '

0 O ( 1 2 3 S (

R

R

R

LOAD 4 5 6 4

LOAD 4 5 6 7

L O A D

T



36


Remote Cohesive Load Center The tripping relay should not operate for 1.15 times the

maximum current flow as calculated by the

transmission owner assuming a 0.85 per unit voltage

and a line phase angle of 30 degrees.

R

R

R

L O A D

T

T

A N S M I S S I O N S

Y S T

M



37


Cohesive Load Center Remote to TransmissionSystem

The Tripping relay should not operate for 1.15 times

the maximum current flow as calculated by the TPSO

assuming a 0.85 per unit voltage and a line phaseangle of 30 degrees.

R

R

R

T

A N S M I S S I O N

S Y S T

M

L O A D

N T



38

Some Possible Mitigation Methods

Must adequately protect system

Increase distance relay maximum torqueangle

Utilize load-tolerant relay characteristics(blinders, lens characteristics, SEL loadencroachment, etc)

Utilize transfer trip for remote backup

Transmission system modifications tofacilitate protection

Others?



39

SPCTF ± Next Distance Relay Activities

All other load responsive relays (230 kV andabove, and lower voltage level critical facilities)

must also not limit practical loading capability

Includes Zone 2 relays, pilot-scheme relays, and

overcurrent relays

DCB Carrier Schemes can improperly operate on

through load if lines are consuming significant real

and reactive power

Will have a different schedule for analysis,

reporting, and mitigation

Must adequately protect electrical system



40

SPCTF Contacts

For detailed questions or suggestions, please contact Bob Cummings ± NERC Staff

[email protected]

609-452-8060

Charles Rogers ± SPCTF Chairman [email protected]

517-788-0027

Mark Carpenter ± SPCTF Vice Chairman [email protected]

817-215-6868 We Need everyone¶s help for us to do the best possible

job!



41

Questions?

Charles Rogers (Consumers Energy) ± Chairman,SPCTF

Bob Cummings (NERC) ± Director ± Reliability

Assessments and Support Services

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