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

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

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)

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

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)

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

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

Double-Ended TWFL for Hybrid Lines Line Data

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

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

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

AG Fault on OHL Section S 𝟖𝟎𝟓,𝟗𝟖𝟕.𝟓𝟒𝟗 ms R Calculated 15.066 mi Actual 15.000 mi Error 350 ft 𝟖𝟎𝟔,𝟎𝟔𝟖.𝟑𝟒𝟏 ms

BG Fault on UGC Section S R

BG Fault on UGC Section S 𝟑𝟖𝟒,𝟎𝟕𝟔.𝟑𝟒𝟏 ms R Calculated 23.008 mi Actual 23.000 mi Error 42 ft 𝟑𝟖𝟒,𝟎𝟒𝟐.𝟖𝟏𝟑 ms

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

AG Fault on OHL Section Example

BG Fault on UGC Section Example

TW Attenuation and Dispersion

Line Energization for Accurate Settings

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)

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)

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 – 107.5 = 81.5 1+2+3 to Terminal R 485.0 3 → 485/2 – 107.5 – 81.5 = 53.5

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