FAULT TYPE SELECTION

Jeff Roberts

April 6 and 9, 2005

Fault-Selection LogicPurpose

• Ensures Single-Pole Trip Security:- SLG vs LLG Faults

• Blocks BG CG for BCG FaultsAvoids Ground Overreach – SPT & 3PT

• Relay Targeting

• Fault Locator Loop Selection

FS1

Real-Time Fault Type Selection Methods

• Overcurrent (Switched Scheme)

• Fault Selection Zones (Switched Scheme)

• Distance Element Torque Analysis

• Angle I0 - Angle I2 Comparison:– Single-Ended (Distance and Directional

Relays)– Double-Ended (Line Current Differential)

From the V and I Shown … Is The System Is Normal or Faulted?

1

R e lay 1

2

3 4

S O U R C E S S O U R C E R

E S E R -15

VA = 66.19 V -13.9° IA = 1.58 A -177.7°VB = 66.24 V -134.1° IB = 1.32 A 63.90°VC = 66.31 V 106.1° IC = 1.58 A -57.6°

Faulted …. Now Can You Determine Which Phase(s) Is(Are) Faulted?

VA1 = 66.25 V -13.9° IA1 = 1.49 A -177.2°

VA2 = 66.24 V -134.1° 3IA2 = 0.27 A 114.7°

VA0 = 66.31 V 106.1° 3I0 = 0.27 A -125.3°

1

R e lay 1

2

3 4

S O U R C E S S O U R C E R

E S E R

m =0.9

R F = 15

-15

What Tools Do You Have Available To You?

• Phase Current Magnitude and Angle

• Phase Voltage Magnitude and Angle

• Sequence Current Magnitude and Angle

• Sequence Voltage Magnitude and Angle

• Apparent Impedance

• Distance Element Pickup Status

Example Fault Type Selection SystemRadial Line

Z S ZL

Relay

FAULTSOURCE S

ZL1 = 8 OhmsZL0 = 24 Ohms

ZS1 = 1 OhmZS0 = 3 Ohms

m (per-unit of ZL)

Many “Loops”

Detect Close-In Phase A-

Ground Faults

AG

BG

CG AB

CA

2

4

0

0

4

0

40

4

R

XLINE ANGLE

SELF-POLARIZED

EXPANDED

CHARACTERISTICS

REACH =300%•Z1L

Fault Location Also

Effects Which Loops Can Detect

Ground Faults

AG

BG

CG

AB

CA

0

0

0

0

R

X LINE ANGLE

REACH =300%•Z1L

100%

50%50%

100%

50%

100%

50%

100%

-15 -10 -5 5 10 15

Line Angle15

10

5

NO LOAD1

7

1

7

7

7

1

R

CACG

BC

AB

BG

X

BCG Fault @ Remote Terminal

CASE # RF 1 0.00 2 0.25 3 0.50 4 1.00

CASE # RF 5 2.00 6 5.00 7 10.00

AG Fault Sequence Components and Connections

Z1

Z2

Z0

3RF

A B C

I0

IA 2

A-GROUND FAULT

I0

I2

(A t the fau lt)

b. SEQ U EN C E C O N N EC T IO ND IAG R AM

a. SEQ U EN C E C U R R EN TPH ASE R ELAT IO N SH IP

c. FAU LT C O N N EC T IO N

IA 1

BCG Fault Sequence Components and Connections

Z1

Z2

Z0

A B C

I0

IA 2

BC-GROUND FAULT

I0

I2

(A t the fau lt)

b. SEQ U EN C E C O N N EC T IO ND IAG R AM

a. SEQ U EN C E C U R R EN TPH ASE R ELAT IO N SH IP

c. FAU LT C O N N EC T IO N

IA 1

3 R F

I1

(R F = 0)

I0 and I2 for AG, BCG Faults

1012PH1

1 2 0

12

0

I2

I0

AG, BCG BG, CAG CG, ABG

0120° 240°2

0

2

Increasing BCG Fault RF Effects

I0 I2

BC-GROUND

Z0

Z2

Z1

I0

BC-GROUND

Z0

Z2

Z1

Z0

Z2

BC-GROUND

Z1

I2

I0

I2

RF=0

RF=4

RF=10

41.1

62.1

RF

RF

RF

A B C

A B C

A B C

FIDS Sectors – Grounded Systems

0°

30°

60°

90°

120°

150°

180°

210°

240°

270°

300°

330°

FSB30

FSA30

FSC30

FSA60

FSA60

FSB60

FSC60

FSC60

FSB60

Fault Selection LogicTolerating Resistance and Non-Homogeniety

• 0 ± 30°: Enable AG, BC Block Others

• 30° to 60°:

• Compare Rg with Selected Rpp

• Select Rpp Using Distance or |IPH-PH|

RGRP1

Past Homework ATP Single-Line

COMTRADE File Evaluation of Faults on Homework System

• (#5) Try1.cfg – Complex Fault(s)

• (#4) Try2abg.cfg – Simultaneous AG and BG Faults on Differing Lines

• (#1) Try3ag.cfg – Reverse AG Fault

• (#2) Try4ca.cfg – Forward CA Fault

• (#3) Try5cag.cfg – Forward CAG Fault

Double Circuit Simultaneous Faults AG & BG

52L I N E 1

S L G F A U L T

I F

I A S I A R

52

52 52L I N E 2

S O U R C E S S O U R C E R

R e lay 1 R e lay 2

m

87L Schemes

Use FTS

Total Current

FTS Sectors

Fault Selection Conclusions

• Overcurrent Type Fault Selection Must Be Set Above Load

• Multiple Distance Element Loops Detect Close-in Ground Faults

• Increasing RF Can Cause Incorrect Phase Selection for Traditional 21 Element Phase Selection

Fault Selection Conclusions(continued)

• Difference Angle Between I0 and I2 Method:

– Correctly Identifies SLG and PPG faults– Can be made very RF tolerant by Rg vs. Rpp

comparison– Independent of protection element reach

settings.

• SPT and 3PT Schemes Require Fault Type Selection Logic