Copyright © BPA and SEL 2014

Locating Faults by the Traveling

Waves They Launch

Edmund O. Schweitzer, III, Armando Guzmán,

Venkat Mynam, Veselin Skendzic, and

Bogdan Kasztenny Schweitzer Engineering Laboratories, Inc.

Stephen Marx Bonneville Power Administration

Some Faults

Are Easy

to Find

Flashed Insulators Are Hard to Find

Accurately Locate Faults With

Traveling Waves

For a fault at 38.16 miles

Method Distance (miles) Difference (miles)

Impedance 34.03 4.13

Traveling wave (TW) 37.98 0.18

Estimate Location From Current

Set 1 3 5 10 15 20

Measured 0.97 3.00 4.7 10 14 20

Not bad for 77 years!!!

“JM Drop” circa 1936

Adheres to Standard

SIS 12 AWG/10-32/5A

Quick Test, 2013

Estimate Location From Impedance

VS

m 1 – mVR

IFIS IR

Line Impedance = ZL

Impedance-Based Methods

• Widely available in line relays today

• No communications required, but need

voltages and currents

• Transients: faster relays and breakers

• Series compensation, mutual coupling,

transposition

• CCVT accuracy and transient response

L Rm ℓ – m

2m

m

3m2(ℓ – m)

Faults Launch Traveling Waves

Currents and Bewley Lattice Diagram BG Fault, June 04, 2013

Mic

rose

co

nd

s

-20 0 20 40 60

Goshen B

(A)

0 20 40 60 80 100

km-10 0 10

0

100

200

300

400

500

600

700

800

900

1000

Drummond B

(A)

Two-End TWFL Method

L R

m

BECKY BECKY

tL tR

L R

1m t – t v

2 l

Automatic Fault Locator (BPA, 1972)

L R

Counter

Start

Stop

Microwave

Receiver

Microwave

Transmitter

Master Terminal Remote Terminal

Wave L Wave R

TW Processing

Unit

TW Processing

Unit

Practical Considerations

• CTs are pretty “hi-fi”, bandwidth > 100 kHz

• CCVTs are not, except at the capacitive

voltage divider tap, but that means new

cabling

• Use currents and two-end method

• Fit naturally in current differential relays

• Re-use same communications channel

Nature of Traveling Waves

• Lightning surges coupling onto line

• Wave launched by fault

• Reflections from discontinuities

• “Messy” electrical breakdown

• Can’t expect “textbook” waveshapes

340 360 380 400 420 440 460–500

–400

–300

–200

–100

0

100

200

300

400

500C

urr

en

t (A

)

Time (μs)

Clean Breakdown: CG Fault

340 360 380 400 420 440 460

–600

–400

–200

0

200

400

600

Cu

rre

nt (A

)

Time (μs)

Precursory Waves: Shield Coupling??

Precursory

Waves Main Flashover

Wave

TW Fault Locator Design Concept

• Filter and sample currents

• Isolate desired mode

• Accurately measure time of arrival

• Exchange with other end, over same 87L

channel

• Calculate location using two-end equation

• Save data

370 372 374 376 378 380 382 384

100

200

300

400

Cu

rre

nt (A

)

Time (μs)

Large Uncertainty

(2 μs = 600 m)

0

Simple Threshold Won’t Work

Differentiator-Smoother Works Great Borrowed Idea From “Leading Edge Tracking”

t

di/dt

ta

t

i

i(t)is(t)

di/dt

Current Arrival

Timei(t) is(t)ta

di/dt

d/dtSmoother

(LPF)

DifferentiatorTime-of-

Peak

Estimator

Interpolate to

50 ns accuracy

Relative Accuracy ~ 50 ns

Mean Error = 17 ns or 8′

Standard Deviation = 32 ns or 16′

R1 t1

R2 t2

Clock Dt = t1 – t2

87L and TWFL Share 64 kb/s Channel

87L87L and TWFL

64 kb/s

network or point-to-point

87L

Wide-Area Time Reference (Network or GPS)

(for TWFL only)

BPA Experience – 161 kV Line

DS1 Microwave Link

SEL-411L

SEL

SEL-411L

SEL

Gunshot Phase Currents at Goshen and Drummond

Goshen Terminal

200

100

0

–100

Curr

en

t

36.832647 36.832697 36.832747

40

20

0

–20

Curr

en

t

36.832647 36.832697 36.832747

–40

Drummond Terminal

“We Know Where Your Faults Are”

Nature of Fault Line Patrol (miles) TW (miles)

Flashover 67.91 68.19

Lead projectile 38.16 37.98

Lightning 66.86 67.25

Flashover 61.50 61.42

Flashover 50.18 50.56

Flashover 59.04 59.04

Accuracy within one to two tower spans

BG Fault Located at 62/10…Irrigation

Closest

Tower

BPA Experience – Tapped Lines

Red

mon

d

Bra

sada

Bro

ther

s Tap

Har

ney

Yew

Ave

. Tap

Ham

pton

Tap

Rile

y Tap

Line Patrol – It Was Like

“Chasing Ghosts on This Line”

Nature of Fault Line Patrol (miles) TW (miles)

Flashover 36.65 36.33

Flashover 36.65 36.76

Flashover 6.92 6.92*

Flashover 91.62 91.76

Flashover 4.94 4.94*

Bird waste 47.1 47.35

*Single-ended fault location

Accuracy within one to two tower spans

Line Patrol Found These

Flashed Insulators

Summary of Typical Errors

Relay Error 50 ns 25′

Timing (clock) 50 ns 25′

Line Length (0.1% of 100 mi) 500′

Speed 0.05% 250′

Allowance for other errors 250′

…on the order of one span

Traveling Wave Fault Locator

• Fits “hand-in-glove” into differential relay

• Easy to set up and use

• Not affected by series caps, mutual

coupling, or very fast clearing

• Complements impedance methods

• Adds to our understanding of lines

TWFL on Cables In Service on 345 kV Underground Cables

Waves Propagate Slower in

Underground Cables

Wave Velocity = 0.48 Times Speed of Light