1. Fault Location EE 526 Venkat Mynam Senior Research Engineer Schweitzer Engineering Laboratories

2. Accurate Fault Location is Critical
Expedite Service Restoration
Reduce outage times
Identify insulator problems
Prevent potential recurring faults
Verify Protective Relay Performance

3. Permanent Fault Need Immediate Attention
We need accurate fault location

4. Temporary Faults Needs Attention Too
Identify & Fix Damaged Insulators-Minimize Fault Recurrence

5. Hard to Find a Flashed Insulator
Fault location investigations

6. Finding Faults

7. Visual Methods

8. Estimate Location From Current
“JM Drop” circa 1936
Approximate fault location was calculated based on system and line parameters

9. Methods in Use Line impedance Based Traveling Wave Based
Measure impedance to fault
Compare it to the actual line impedance
Traveling Wave Based
Measure wave arrival time

10. System One-Line and Circuit Representation of System Fault

11. Modified Takagi Method-Single Ended (Negative Sequence)
Multiply by I2 and save Imaginary part
Zero
For:
Rf=0 or system is homogeneous

12. IEEE Guide Defines Homogeneous System
“A transmission system where the local and remote source impedances have the same angle as the line impedance”

13. Single End Impedance Method
Accuracy of zero-sequence line impedance Effect of zero-sequence mutual coupling from parallel lines Time synchronization Communication Radial topology  
Fault resistance System nonhomogeneity Accuracy of measurements Accuracy of positive-sequence line impedance       

14. SE Impedance Fault Location Phase-Ground Faults
𝑚𝐴𝐺= 𝐼𝑚 𝑉𝐴𝐺∙ 𝐼 2 𝑎 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐴𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2 𝑎 ∗
𝑚𝐵𝐺= 𝐼𝑚(𝑉𝐵𝐺∙ 𝐼 2 𝑏 ∗ ) 𝐼𝑚(𝑍1𝐿∙(𝐼𝐵𝐺+𝑘0∙𝐼𝐺)∙ 𝐼 2 𝑏 ∗ )
𝑚𝐶𝐺= 𝐼𝑚 𝑉𝐶𝐺∙ 𝐼 2 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐶𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2 𝑐 ∗
𝐼 2 𝑏 =𝑎∙𝐼 2 𝑎 𝐼 2 𝑐 = 𝑎 2 ∙𝐼 2 𝑎

15. SE Impedance Fault Location Multi-Phase Faults
𝑚𝐴𝐵= 𝐼𝑚 𝑉𝐴𝐵∙ 𝑗∙𝐼 2 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ 𝑗∙𝐼 2 𝑐 ∗
𝑚𝐵𝐶= 𝐼𝑚 𝑉𝐵𝐶∙ (𝑗∙𝐼 2 𝑎 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ (𝑗∙𝐼 2 𝑎 ) ∗
𝑚𝐶𝐴= 𝐼𝑚 𝑉𝐶𝐴∙ (𝑗∙𝐼 2 𝑏 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐶𝐴∙ (𝑗∙𝐼 2 𝑏 ) ∗
𝑚3𝑃= 𝐼𝑚 𝑉∅∅∙ 𝐼∅∅ ∗ 𝐼𝑚 𝑍1𝐿∙𝐼∅∅∙ 𝐼∅∅ ∗
𝐼 2 𝑏 =𝑎∙𝐼 2 𝑎 𝐼 2 𝑐 = 𝑎 2 ∙𝐼 2 𝑎

16. Fault Loop Selection and Reporting
Select appropriate Fault Loop
Report a single fault location value
Select a window of data from the fault data
Provide the average value of fault location computed from the selected window

17. Modified Takagi Method-Multi Ended (Using Remote terminal current)
Multiply by I2 and save Imaginary part
THIS IS ZERO

18. Multi-End I2 Total Current 
Fault resistance System nonhomogeneity Accuracy of measurements Accuracy of positive-sequence line impedance
Accuracy of zero-sequence line impedance Effect of zero-sequence mutual coupling from parallel lines Time synchronization Communication      

19. ME_I Impedance Fault Location Phase-Ground Faults
𝑚𝐴𝐺= 𝐼𝑚 𝑉𝐴𝐺∙ 𝐼 2𝑇 𝑎 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐴𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2𝑇 𝑎 ∗
𝑚𝐵𝐺= 𝐼𝑚(𝑉𝐵𝐺∙ 𝐼 2𝑇 𝑏 ∗ ) 𝐼𝑚(𝑍1𝐿∙(𝐼𝐵𝐺+𝑘0∙𝐼𝐺)∙ 𝐼 2𝑇 𝑏 ∗ )
𝑚𝐶𝐺= 𝐼𝑚 𝑉𝐶𝐺∙ 𝐼 2𝑇 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙ 𝐼𝐶𝐺+𝑘0∙𝐼𝐺 ∙ 𝐼 2𝑇 𝑐 ∗
𝐼 2𝑇 𝑏 =𝑎∙𝐼 2𝑇 𝑎 𝐼 2𝑇 𝑐 = 𝑎 2 ∙𝐼 2𝑇 𝑎
𝐼2𝑇=𝐼2𝐿𝑜𝑐𝑎𝑙+𝐼2𝑅𝑒𝑚𝑜𝑡𝑒

20. ME Impedance Fault Location Multi-Phase Faults
𝑚𝐴𝐵= 𝐼𝑚 𝑉𝐴𝐵∙ 𝑗∙𝐼 2𝑇 𝑐 ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ 𝑗∙𝐼 2𝑇 𝑐 ∗
𝑚𝐵𝐶= 𝐼𝑚 𝑉𝐵𝐶∙ (𝑗∙𝐼 2𝑇 𝑎 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐵𝐶∙ (𝑗∙𝐼 2𝑇 𝑎 ) ∗
𝑚𝐶𝐴= 𝐼𝑚 𝑉𝐶𝐴∙ (𝑗∙𝐼 2𝑇 𝑏 ) ∗ 𝐼𝑚 𝑍1𝐿∙𝐼𝐶𝐴∙ (𝑗∙𝐼 2𝑇 𝑏 ) ∗
𝑚3𝑃= 𝐼𝑚 𝑉∅∅∙ 𝐼∅∅𝑇 ∗ 𝐼𝑚 𝑍1𝐿∙𝐼∅∅∙ 𝐼∅∅𝑇 ∗
𝐼 2𝑇 𝑏 =𝑎∙𝐼 2𝑇 𝑎 𝐼 2𝑇 𝑐 = 𝑎 2 ∙𝐼 2𝑇 𝑎
𝐼2𝑇=𝐼2𝐿𝑜𝑐𝑎𝑙+𝐼2𝑅𝑒𝑚𝑜𝑡𝑒
𝐼∅∅𝑇 =𝐼∅∅𝐿𝑜𝑐𝑎𝑙+𝐼∅∅𝑅𝑒𝑚𝑜𝑡𝑒

21. Multi Ended Negative Sequence Using Remote terminal voltage and current
ref
V2F +

22. Use Synchronized Measurements to Calculate Voltage at Fault Point

23.         Double End With V2 and I2
Fault resistance System nonhomogeneity Accuracy of measurements Accuracy of positive-sequence line impedance
Accuracy of zero-sequence line impedance Effect of zero-sequence mutual coupling from parallel lines Time synchronization Communication      

24. Multi-End Fault Location That Does Not Require Data Alignment
Each Relay Receives:
Magnitude and Angle of Z2R
½I2R½

25. Local and Remote Data Necessary for Fault Location
Rearrange Above Equation to Form a Quadratic Equation
Solve Quadratic for Fault Location m
Download Paper

26. Multi-End Methods Needs Time Synchronized Data
Synchrophasors
Synchronized samples
Devices with data acquisition synchronized to a common time source
Fixed sampling rate

27. Series Compensated Lines
Line Side PT
Bus Side PT
Challenges
Steady State
Transient (phasor estimate is not stable)
Subsynchronous
MOV and bypass breaker switching
Download Paper

28. Three-Terminal Line

29. Reduce From Three-Terminal Line to Two-Terminal Equivalent
V2_SP = V2S – Z2L_SP • I2S
V2_TP = V2T – Z2L_TP • I2T
Same Result
V2_UP = V2U – Z2L_UP • I2U

30. Use Two-Terminal Equivalent to Solve for m
I2_Eq = I2T + I2U
V2_Eq = V2_TP
Solve for m using SE or Multi-terminal (ME_I, ME)
ME_I

31. Mutually Coupled Lines
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32. Composite Lines Identifies faulted line section
Calculates distance to fault

33. Intersection of Voltage Profiles Identifies Faulted Section

34. Calculate Distance to Fault Within Faulted Section using ME method
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35. Impedance Method Approach Summary
Measure VA, VB, VC, IA, IB, IC
Extract fundamental components
Determine phasors and fault type
Apply impedance algorithm

36. Impedance Fault Location Methods
Single-End Method using local voltage and currents SE
Multi-End Method using local voltage and currents, and remote
currents
MEI
Multi-End Method using local and remote voltage and currents ME

37. Some of the Challenging Situations for Z based Fault Location Methods
Short faults: faster relays and breakers- phasor estimate is not stable
Faults associated with time-varying fault resistance-phasor estimate is not stable
Series compensation

38. Short Duration Faults Raw-Blue, Cosine Filtered-Green
Magnitude of Filtered Quantity-Red

39. Lightning and Faults Launch Traveling WavestL tR
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40. Double Ended TW Fault Location

41. Single-End TW Fault Locator

42. Image courtesy of Google
Results From Field
117.11km, 161 kV line
18 sections with 4 different tower configurations
Challenges with existing impedance based fault location methods
Image courtesy of Google

43. Fault Location Results (161kV, 117.11km long line)TW
Patrol
SE_Z
ME_Z_I
ME_Z CG
109.74
109.29
105.44
106.24
106.56 BG
61.12
61.41
54.75
60.69
60.70
108.23
107.60
101.59
106.43
98.85
98.98
95.20
98.37

44. Temporary Fault Due to Insulator Flashover

45. Insulator Flashover