Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling...

25
1 Copyright © SEL 2015 Copyright © SEL 2015 Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories, Inc. Example 100 Mile Transmission Line Z 1S = 2 88° Z 1L1 = Z 1L2 = 8 84° Z 1R = 2 88° Z 0S = 2 88° Z 0L1 = Z 0L2 = 24 80° Z 0R = 2 88° Z 0M = 16 78°

Transcript of Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling...

Page 1: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

1

Copyright © SEL 2015Copyright © SEL 2015

Line Protection: From Phasors to Traveling Waves

Karl ZimmermanTechnical Support Director

Schweitzer Engineering Laboratories, Inc.

Example 100 Mile Transmission Line

Z1S = 2 Ω 88° Z1L1 = Z1L2 = 8 Ω 84° Z1R = 2 Ω 88°Z0S = 2 Ω 88° Z0L1 = Z0L2 = 24 Ω 80° Z0R = 2 Ω 88°

Z0M = 16 Ω 78°

Page 2: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

2

Focus for Today

• Benefits of faster line protection

• Limitations of present-day phasor-based protection

• Principles of time-domain protection

• New Time-Domain Line Protection Relay

Already Pretty Fast – Why Faster?

• Higher power transfers(investment dollars saved)

• Reduced equipment wear (generators and transformers)

• Improved safety

• Reduced property damage

• Improved power quality

Page 3: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

3

How Much Faster?

• Present-day relays

Based on phasors

Operate in 0.5–1.5 cycles

• Present-day breakers operate in 2 cycles

• Ultra-high-speed fault clearing

Consistent relay operating times

2 ms (TW) to 4 ms (differential equations)

Subcycle times from future dc breakers

Phasor-Based Protection Makes Sense

• Power systems were traditionally designed and modeled for steady-state operation at system frequency

• “Forcing functions” are at system frequency

• Instrument transformers are rated at system frequency

• CCVTs are band-pass devices

Page 4: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

4

Speed of Present-Day Relays

• Phasors represent steady state

• Determining steady state takes time

This is what we know if we trip in 0.5 cycles

Speed of Present-Day Relays

• Phasors represent steady state

• Determining steady state takes time

Page 5: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

5

Speed of Present-Day Relays

• Phasors represent steady state

• Determining steady state takes time

• Shorter windows are faster but less accurate

Line Protection Using POTT Scheme With 21/67 Elements or

87L Scheme

Page 6: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

6

Zr

Z

dZ

Zp

ZS1

Dynamic Expansion

Basic Directional Element (32) Principle

Page 7: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

7

Symmetrical Components for Single-Line-to-Ground Fault

Negative-Sequence

Impedance Used to Determine

Fault Direction

2 2

2measured 22

Re V • 1 Z1ANG•IZ

I

L2Z Angle

Page 8: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

8

Protection Scheme Trip Time for Comm. Scheme Using 21/67

m (per-unit distance to fault)

TP

TT

(cy

cles

at 6

0 H

z) 1.5

0.5

1.0

0 0.25 0.50 1.00.75

Phase-to-Ground Fault

Phase-to-Phase Fault

Two-Terminal Digital Line Current Differential (87L) Application

Page 9: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

9

Alpha Plane Used for 87L Scheme

Angle

Rad

ius

Protection Scheme Trip Time for 87L

m (per-unit distance to fault)

TP

TT

(cy

cles

at

60 H

z) 1.5

0.5

1.0

0 0.25 0.50 1.00.75

87L Average (phase to ground)

87L Average (phase to phase)

87L Minimum (phase to ground)

87L Minimum (phase to phase)

Page 10: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

10

Phasor and Time-Domain PrinciplesSimilarities and Differences

Algorithm Phasor-Based Differential Equations Traveling Waves

Spectrum 50 / 60 Hz 1 kHz 100 kHz

Filtering

Sampling 16–32 s/c 10 kHz 1 MHz

Line theory

Operating time ~ 1 cycle A few milliseconds 1 ms

Requirements for CTs and PTs

Low Moderate High

TD21 Underreaching

Communications-independent

Comm-Based Scheme Using 32 (directional) TD32 and TW32 for direction

Fast communications as a teleprotection channel

TW87 Current-only

Direct fiber as a channel (100 Mbps)

GPS-independent

Time Domain: Speed With Security

Page 11: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

11

• Full-scale 1 MHz sampling

• TWs processed every microsecond

• -quantities processed every 0.1 ms

• Protection logic runs every 0.1 ms

Time Domain Uses High-Speed Data

Traveling-Wave Principles

Page 12: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

12

L R

m

tL tR

Lightning and Faults Launch Traveling Waves

L R1

m t – t v2

L Rm ℓ – m

2(ℓ – m)

2m

2ℓ – m

3(ℓ – m)

ℓ – m2m

m

3m2(ℓ – m)

Low Z Low Z

t0

tL

tR

Polarity of Waves

Page 13: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

13

Deriving TW87 Operating Principles Three Scenarios to Consider

–20 –10 0 10 20 30 40–200

0

200

Vol

tage

(V

)

–20 –10 0 10 20 30 40–5

0

5

Cur

rent

(A

)

Time (ms)

External Fault Behind Local Relay Remote Terminal

Page 14: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

14

Vol

tage

(V

)C

urre

nt (

A)

External Fault Behind Local RelayLocal Terminal

TW fault information is contained in thefirst 1–2 milliseconds of the fault

TW87 Principle – External Fault (F1)

Line propagation time

m87 = 1 pu

Loca

l Cur

rent

(A

)

Rem

ote

Cur

rent

(A

)

Page 15: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

15

TW87 Is Secure for External Fault (F1)

IL (A) IR (A) IDIF (A) IRST (A) m87 (pu)

F1

A 1.41 0.75 0.66 2.16 1.0

B 0.40 0.40 0.01 0.80 1.0

C 0.38 0.38 0.00 0.76 1.0

Loca

l TW

(A

)

Rem

ote

TW

(A

)

–200 0 200 400 600 800 1000–5

0

5

10

Time (µs)0 200 400 600 800 1000

–5

0

5

10

TW87 Principle – Internal Fault (F2)

Line propagation time

Line propagation time

m87 < 1 pu

Page 16: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

16

IL (A) IR (A) IDIF (A) IRST (A) m87 (pu)

F2

A 1.22 0.76 1.98 1.22 0.4

B 0.51 0.39 0.90 0.51 0.4

C 0.54 0.38 0.92 0.54 0.4

TW87 Operates in 1.5 ms

Loca

l TW

(A

)

Rem

ote

TW

(A

)TW87 Principle – External Fault (F3)

Line propagation time

Line propagation time

m87 < 1 pu

Loca

l Cur

ren

t (A

)

Rem

ote

Cur

rent

(A

)

Page 17: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

17

L R

F3

IL (A) IR (A) IDIF (A) IRST (A) m87 (pu)

F3

A 0.92 0.53 1.45 1.70 0.3

B 0.31 0.27 0.58 0.74 0.3

C 0.30 0.28 0.57 0.72 0.3

TW87 Is Secure for External Fault (F3)

L F RtF tF

Local TW Remote TW

Trip in 1.2 ms

Time (µs)

321

972

TW87 Operating Time on a 117 km Line

75

Page 18: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

18

Processing Is Fast TW87 Speed Depends on Line Length

TW

87 T

ime

(ms)

Incremental Quantity Directional Element (TD32)

Page 19: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

19

Forward Faultv Is Opposite Polarity to Replica Current

Reverse Faultv Is Same Polarity as Replica Current

Page 20: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

20

v and i Are of Opposite Polarities for Forward Faults

0 2 4 6 8 10–100

–50

0

50

100

–100

–50

0

50

100

Time (ms)

0 2 4 6 8 10–100

–50

0

50

100

–100

–50

0

50

100

Time (ms)

Incremental Quantity Distance Element (TD21)

Page 21: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

21

Fault at the Reach|vF| Is Equal to |vPRE|

Fault Within the Reach|vF| Is Greater Than |vPRE|

Page 22: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

22

Fault Beyond the Reach|vF| Is Lower Than |vPRE|

Competitive TestingTime-Domain vs. Phasors

Page 23: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

23

Vol

tage

(V

)C

urr

ent

(A

)

TD21 amd TD32 Operate Faster 230 kV, 159 km, Fault at 18%

FSCC2

C1

L

Line voltage

Relay voltageStep-down transformer

Compensating reactor

Extracting Polarity of the First Wave

Page 24: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

24

TD21 and TW87 ElementsComplement One Another

SE

L-T

400L

Tim

e (m

s)

TD21 Operates in Less Than 8 ms for a 100 Ohm Fault

Page 25: Line Protection: From Phasors to Traveling Waves · Line Protection: From Phasors to Traveling Waves Karl Zimmerman Technical Support Director Schweitzer Engineering Laboratories,

25

Copyright © SEL 2015Copyright © SEL 2015

Questions?