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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
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Some Faults
Are Easy
to Find
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Flashed Insulators Are Hard to Find
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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
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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
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Estimate Location From Impedance
VS
m 1 – mVR
IFIS IR
Line Impedance = ZL
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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
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L Rm ℓ – m
2m
m
3m2(ℓ – m)
Faults Launch Traveling Waves
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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)
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Two-End TWFL Method
L R
m
BECKY BECKY
tL tR
L R
1m t – t v
2 l
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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
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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
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Nature of Traveling Waves
• Lightning surges coupling onto line
• Wave launched by fault
• Reflections from discontinuities
• “Messy” electrical breakdown
• Can’t expect “textbook” waveshapes
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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
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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
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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
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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
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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
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Relative Accuracy ~ 50 ns
Mean Error = 17 ns or 8′
Standard Deviation = 32 ns or 16′
R1 t1
R2 t2
Clock Dt = t1 – t2
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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)
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BPA Experience – 161 kV Line
DS1 Microwave Link
SEL-411L
SEL
SEL-411L
SEL
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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
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“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
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BG Fault Located at 62/10…Irrigation
Closest
Tower
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BPA Experience – Tapped Lines
Red
mon
d
Bra
sada
Bro
ther
s Tap
Har
ney
Yew
Ave
. Tap
Ham
pton
Tap
Rile
y Tap
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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
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Line Patrol Found These
Flashed Insulators
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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
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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
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TWFL on Cables In Service on 345 kV Underground Cables
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Waves Propagate Slower in
Underground Cables
Wave Velocity = 0.48 Times Speed of Light