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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