1. Locating Faults Before the Breaker Opens – Adaptive Autoreclosing Based on the Location of the Fault
Bogdan Kasztenny, Armando Guzmán, Mangapathirao V. Mynam, and Titiksha Joshi Schweitzer Engineering Laboratories

2. Autoreclosing Controlled by Fault Location
Hybrid lines with overhead and cable sections Lines terminating at large generating stations Lines with public safety concerns Lines with sections having low success rate of autoreclosing

3. Impedance Fault-Locating Methods General Accuracy Limitations
CT and VT ratio errors
Phasor measurement errors
Finite accuracy of line data
Fault resistance (single-ended methods)
Changes in fault resistance
Finite accuracy of data alignment (double-ended methods)

4. Impedance Fault-Locating Methods Accuracy Limitations for Hybrid Lines
Nonhomogeneity
Different Z1 for UGC and OHL
Different Z0 / Z1 for UGC and OHL
Z0 uncertain and variable
Z0 may depend on the fault current

5. Traveling-Wave Fault Locators
Pinpoint faults to the nearest tower (300 m or 1,000 ft)
Applied to thousands of lines
Excellent track record
Fault located by a TWFL (photo courtesy of BPA, 2017)

6. Double-Ended TWFL Principle of Operation
M= t S ∙ LL TWLPT
LL − M= t R ∙ LL TWLPT
M= LL 2 ∙ 1+ t S − t R TWLPT

7. TWFL Device Is Accurate to 1/30th of Tower Span!
Error in Meters
No of Cases

8. Double-Ended TWFL for Hybrid Lines Line Data

9. Double-Ended TWFL for Hybrid Lines Simple Correction
1) Calculate M* as if the line were homogeneous
2) Calculate t* as
t ∗ =TWLPT M ∗ LL
t ∗ = 1 2 TWLPT+ t S − t R
3) Project t* on the non-homogeneity characteristic to obtain true M

10. Autoreclosing Control Based on Fault Location
BLOCK AR M1 M2 M1 M2

11. AG Fault on OHL Section S Section Type Length (mi)
Propagation Time (ms) 1
Overhead
20.00
107.50 2
Cable
8.00
81.50 3
10.00
53.75
Total
Hybrid
38.00
242.75 R

12. AG Fault on OHL Section S
𝟖𝟎𝟓,𝟗𝟖𝟕.𝟓𝟒𝟗 ms R
Calculated mi Actual mi Error 350 ft
𝟖𝟎𝟔,𝟎𝟔𝟖.𝟑𝟒𝟏 ms

13. BG Fault on UGC Section S R

14. BG Fault on UGC Section S
𝟑𝟖𝟒,𝟎𝟕𝟔.𝟑𝟒𝟏 ms R
Calculated mi Actual mi Error 42 ft
𝟑𝟖𝟒,𝟎𝟒𝟐.𝟖𝟏𝟑 ms

15. Current TW Reflection and Transmission
Reflected Incident = Z C1 − Z C2 Z C1 + Z C2
Transmitted Incident = 2∙Z C1 Z C1 + Z C2
100 A arrives on OHL section: 160 A continues on UGC and 60 A reflects back on OHL
100 A arrives on UGC section: 40 A continues on OHL and 60 A (-) reflects back on UGC

16. AG Fault on OHL Section Example

17. BG Fault on UGC Section Example

18. TW Attenuation and Dispersion

19. Line Energization for Accurate Settings

20. Line Energization for Accurate Settings Energizing From Terminal S
2*(Section 1)
2*(Section 2)
2*(Section 3)
2*(Section 1 + Section 2)
2*(Section 1 + Section 2 + Section 3)

21. Line Energization for Accurate Settings Energizing From Terminal R
2*(Section 3)
2*(Section 2)
2*(Section 1)
2*(Section 3 + Section 2)
2*(Section 1 + Section 2 + Section 3)

22. Settings Calculation Section Propagation Times
Round Trip
Time (ms)
Section TWLPT (ms) 1
to Section 1 – 2 transition
215.0
1 → 215/2 = 107.5
1+2
to Section 2 – 3 transition
378.0
2 → 378/2 – = 81.5
1+2+3
to Terminal R
485.0
3 → 485/2 – – = 53.5

23. Conclusions
Double-ended TW fault locators work very well on hybrid lines
Line energization test allows accurate TWFL settings
TW fault locators working in real time enable adaptive, location-dependent autoreclosing
Now you can apply single-pole tripping and autoreclosing on hybrid lines