An Introduction to Completinga NERC PRC-026-1 StudyFor Traditional Generator Applications

Presented by: Matt Horvath, P.E.March 26, 2019

TEXAS A&M PROTECTIVE RELAY CONFERENCE

2

Introduction

NERC Protection and Control (PRC) Standards• 2003 Northeast Blackout

Overview• PRC-026-1 Standard• Power Swings• Example Study• Impact on Settings

NERC PRC-026-1 Overview

4

Summary

Protection Restraint for Stable Power Swings• Applies to Bulk Electric System Facilities:

» Transmission Lines» Transformers» Generators

• System Planning (R1)» Effective Date: Jan 1, 2018

• System Protection (R2 – R4)» Effective Date: Jan 1, 2020

• Attachments A and B

5

PRC-026-1 Requirement R1

Planning Coordinator Criteria1. For generator(s) with an angular stability constraint

A. System Operating Limit (SOL)B. Remedial Action Scheme (RAS)

2. Element being monitored as part of a SOLA. NERC FAC-014-2

3. Element that forms a boundary of an islandA. Underfrequency Load Shedding AssessmentB. Trip due to angular instability

4. Element identified that will trip for stable or unstable swings (during simulated disturbance)

6

PRC-026-1 Requirement R2

2.1 – Notification Received• Determine if element meets Attachment B criteria

» Unless Analyzed within the past 5 years2.2 – Trip Event• Determine if element meets Attachment B criteria

Applicable elements• Phase Distance • Phase-Overcurrent • Out-of-Step Tripping (OOST)• Loss-of-Field (LOF)

Introduction to Power Swings

8

Two Source Model and Power Transfer

Es ER

Xs XL XR

P

0 3 0 6 0 9 0 1 20 1 50 1 800

0 .5

1

Power Angle Curve

Power Angle (deg)

Pow

er T

rans

fer (

p.u.

)

9

Power Angle Acceleration & Disturbances

Receiving SourceSending Source

New Operating Point

Max Angular Displacement

Angular Displacement:

Reference Angle

First Operating Point

10

Power Swings in the R-X Plane

4− 2− 0 2 4

4−

2−

2

4Impedance CircleReceiving Source ErSending Source Es

Resistance (R)

Rea

ctanc

e (X

) ZL

ZR

ZS

11

Unstable Power Swing Effects on A Gen

4− 2− 0 2 4

4−

2−

2

4Impedance CircleReceiving Source ErSending Source Es

Resistance (R)

Rea

ctanc

e (X

) ZL

ZR

ZS

Example PRC-026-1 Anlaysis

13

Simplified Study Process

Obtain Facility Data

Calculate Unstable Power

Swing Region (UPSR)

Plot Elements Against UPSR

Compliance Evaluation

Document Compliance

Yes

NoMitigation

14

Facility & Data

• Generator• GSU• POI• Settings

• LOF• OOS• Distance

• Tap Ratios• Drawings

100 MVA13.8 kV

GENGEN Reactances:

X’d: 0.39 puX’’d: 0.33 pu

GSU Transformer

230 kV13.2 kV

90/105/130 MVA

GSU Reactance: 0.143 pu

POI

3-PH Fault: 18,053 A @ 85°

GEN Relay

To 230 kV – Switchyard

BKR

15

Unstable Power Swing Region

Attachment B Criteria

Stable Swing Region

Stable Swing Region

Unstable Swing Region

Unstable Swing Region

• Total System Impedance

• Instrument Transformation Ratio

16

Unstable Power Swing Region

18− 14.4− 10.8− 7.2− 3.6− 0 3.6 7.2 10.8 14.4 1818−

14.4−

10.8−

7.2−

3.6−

0

3.6

7.2

10.8

14.4

18

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

Upper Loss of Synchronism Circle

Lens

Lower Loss of Synchronism Circle

10− 0 10

10−

10

Impedance CircleReceiving Source ErSending Source EsApparent Load ZsysLeft Lens SideRight Lens SideUpper CircleLower Circle

Resistance (R)

Rea

ctan

ce (X

)

20− 16− 12− 8− 4− 0 4 8 12 16 2020−

16−

12−

8−

4−

0

4

8

12

16

20

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

1. Upper Circle• S-R Ratio: 1.43

2. Lower Circle• S-R Ratio: 0.7

3. Lens• Maintains 120°• S-R: 0 to 1.0 pu

17

LOF Element (ANSI 40)

Zone 1• High Speed

Zone 2• Time Delayed

11.5− 9.2− 6.9− 4.6− 2.3− 0 2.3 4.6 6.9 9.2 11.5

24−

21.4−

18.8−

16.2−

13.6−

11−

8.4−

5.8−

3.2−

0.6−

2

Zone 1Zone 2

Res istance

Rea

ctan

ce

Xd

X’d2

18

LOF Element Compliance

Gen Impedance Parameters

Non-Compliance:• Small GSU

Impedance• Small System

Impedance

25− 20− 15− 10− 5− 0 5 10 15 20 2525−

20−

15−

10−

5−

0

5

10

15

20

25

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

20− 16− 12− 8− 4− 0 4 8 12 16 2020−

16−

12−

8−

4−

0

4

8

12

16

20

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

19

Phase Distance Element (ANSI 21P)

• Backup Protection• Zone1

• High Speed• For GSU

• Zone 2• Transmission• Time Delayed

3− 1.4− 0.2 1.8 3.4 5

2−

0.2−

1.6

3.4

5.2

7Line ZZone 1Zone 2

Resistive Reach

Reac

tive

Reac

h

20

21P Element Compliance

• System Component Impedances

• Zone 1 –Contained

• Zone 2 –Time Delayed

5− 4− 3− 2− 1− 0 1 2 3 4 55−

4−

3−

2−

1−

0

1

2

3

4

5

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

21

OOS Element (ANSI 78)

Single Blinder Method• Impedance Circle• Part 1: Mho Circle

• Forward Reach• Reverse Reach

• Part 2: Blinders• 120° Power Angle• Tripping Threshold

5− 0 5

5−

5

Resistance

Reac

tanc

e120°

22

OOS Element Compliance

25− 20− 15− 10− 5− 0 5 10 15 20 2525−

20−

15−

10−

5−

0

5

10

15

20

25

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

23

OOS Element Mitigation

Four Factors1. Gen Reactance2. Fault Contingency3. Rounding Errors4. Blinder Limitation

5− 4− 3− 2− 1− 0 1 2 3 4 55−

4−

3−

2−

1−

0

1

2

3

4

5

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

5− 4− 3− 2− 1− 0 1 2 3 4 55−

4−

3−

2−

1−

0

1

2

3

4

5

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

4− 3.2− 2.4− 1.6− 0.8− 0 0.8 1.6 2.4 3.2 44−

3.2−

2.4−

1.6−

0.8−

0

0.8

1.6

2.4

3.2

4

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

4− 3.2− 2.4− 1.6− 0.8− 0 0.8 1.6 2.4 3.2 44−

3.2−

2.4−

1.6−

0.8−

0

0.8

1.6

2.4

3.2

4

Resistive Reach (Ohms-sec)

Rea

ctiv

e Rea

ch (O

hms-

sec)

24

Final Thoughts & Observations

• Protective Relaying Impact• Exclusions (Attachment A)• Changing System Source Impedance

25

Conclusion

• PRC-026 Triggers• Evaluation Method (UPSR)• PRC-026 vs. Industry Guidelines• Source Impedance Not Constant• Impact on Relay Settings• Effective Dates:

• R1 – January 1, 2018• R2 - R4 – January 1, 2020

Questions

Thank you for your time and attention