© 2019 SEL and AEP
Mystery Solved: Five Surprises Discovered With Megahertz Sampling and Traveling-Wave Data Analysis
E. O. Schweitzer, III, V. Skendzic, A. Guzmán, M. V. Mynam, and J. L. Eternod
Schweitzer Engineering Laboratories, Inc.
Yanfeng GongAmerican Electric Power
• Detection of surges produced by lightning• LOCATION of lightning-induced surges• Breaker restriking and waves launched• HV transients• HV transients we located
MHz Sampling, 18-Bit Resolution, Absolute TimeMillisecond Protection, 100 ft Fault Locating, Greater Visibility
Clarke Components Work for Traveling WavesSymmetrical Components Don’t
α β 0
Can’t use symmetrical components because I1 and I2depend on the “a” operator…which only works with phasors
One Event Reveals Precursor Lightning Surges, BG Fault, and Breaker Restrike
Volta
ge (k
V)
0
100
200
–200
–100
Cur
rent
(A)
0
4000
–4000
8000
500–50 Time (ms)
Ib
Iα and I0 Components Dominate Ground Fault
0
8000
–4000
Cur
rent
(A)
0
–4000
8000
500–50 Time (ms)
Cur
rent
(A)
4000
4000Ib
IαI0
Differentiator-Smoother Accentuates Transientsand Attenuates System Frequency
t
di/dt
tat
i
i(t)is(t)
di/dt
Current Arrival Timei(t) is(t)
tadi/dt
d/dtSmoother
(LPF)Differentiator Time-of-
Peak Estimator
Interpolate to50 ns accuracy
0
500–50 Time (ms)
Cur
rent
(A)
Differentiator-Smoother Accentuates Transientsand Attenuates System Frequency
4000
–4000
0400
–400
0400
–400
Ib
Iα
I0
Rescaling I0 Reveals Prefault Transients18-bit resolution provides excellent dynamic range
500–50 Time (ms)
Cur
rent
(A)
Ib0
4000
–4000
0400
–400
0
20
–10–20
10
Iα
I0
Cur
rent
(A)
0
40
0
–40
–4
Similar Transients in All Three Phases: I0BPA Verifies Lightning Was Nearby
I0
80
–80
–8
–12
4
–36 –34Time (µs)–35
Cur
rent
(A)
0
400
0
–400
–400
800
–800
–800
400
Lightning Triggers BG Fault at T = 0Reflections From the Fault and Remote Terminal
0 Time (µs)100 200 300 400 500
Reflection from fault
Reflection from remote terminal
Iα
TW Fault Locator Reported Fault 65.5 km
From GoshenBPA Verified Location
0
Tim
e (µ
s)
200
400
600
800
1000
1200
1400
Cur
rent
(A)
0
100
0 Time (ms)
Breaker Restrike Delays Fault Clearing ½ CycleVo
ltage
(kV)
200
–100
–200
20 40 60
0
40002000
6000
–2000
Ib
40 45 50 55Time (ms)–4000
–2000
0
2000
4000
Cur
rent
(A)
47.2 47.4 47.6 47.8 48 48.2 48.4 48.6Time (ms)
–2000
–1500
–1000
–500
0
Breaker Restrike Delays Fault Clearing ½ Cycle
Restrike Reflectionfrom fault
Reflection from remote end
Restrike Launches WaveWhich Bounces Off Fault
and the Remote End Tim
e (μ
s)
–200
0
200
400
600
800
10000 50 100
Distance From Local Terminal (km)
RestrikeFault
Restrike reflected from fault
Restrike reflected from remote end
Location of Lightning-Induced Surges
MHz Records Track Lightning Storm as It Moves Across CFE 400 kV System
Over 30 records triggered in 35 minutes with NO faults
R
MID
IBD CHM
TMD
223.8 km
33.6 km195.2 km 102 km
20 km
5.6 km
144 km
R
102 km
144 km
Each Record Shows Multiple Transients Both on Voltages and Currents
Cur
rent
(A)
0200
0 Time (ms)
Volta
ge (k
V)
400
–200–400
0
200100
–200
50 100
–100
300
I0 Dominance Suggests Lightning CFE Verifies Lightning Was NearbyC
urre
nt (A
)
0
200
0 Time (µs)
–200
0
80
40
–80
–40
200 400 600
All Recorded Transients Share Common Shape
I0
No fault,so only reflection
is from remote end
Double-Ended Fault Locating Detects
Location of Lightning Activity
–500
0
500
1000
1500
2000
MID
0 100 200Distance From MID (km)
TMD
Tim
e (μ
s)
Transients Move Across System Like a Storm!
21:50 22:00 22:10 22:20 22:30Local Time (hh:mm)
90
95
100
105
110
115
120
125
Dis
tanc
e Fr
om M
ID (k
m)
High-Voltage Transients
Sudden Onset of Transients but No Faults
R
MID
IBD CHM
TMD
223.8 km
33.6 km195.2 km 102 km
20 km
5.6 km
144 km
R
102 km
144 km
Transients on Voltages and Currents Confirm System Disturbance, not Secondary Wiring
Cur
rent
(A)
0200
0 Time (ms)
Volta
ge (k
V)
400
–200–400
0
800
400
–800100 150
–400
50
• Wave propagates from MID toward TMD
• Source is behind MID• Most likely at MID bus
Transients Originate Outside the Line Zone
Tim
e (μ
s)
–200
0
200
400
600
800
1000
1200
1400
1600
MID
0 100 200Distance From MID (km)
TMD
Source of transient unknown Investigation in progress
AEP Engineers Concerned About 765 kV TransientsOscillogram shows first of three records, in 15 minutes;
Second one was similarC
urre
nt (A
)
0
0 Time (ms)
Volta
ge (k
V)
0
2000
600
–2000
200 400–200
–2000
2000
First and Second Events Triggered by Disconnect Closing; Third by Breaker Closing
Reactor Breaker
Disconnect
R
39.7 kmLine Trap
16.3 km 187.4 km
Station 1
Station 2 Station 3
Station 4
Cur
rent
(A)
0
0Time (ms)
200–200
2000
1000
–2000
–1000Closing disconnecttriggered a flurry of transients.Breaker closing produced clean transients.
Here’s the Third Record…When Reactor Breaker Closed
Cur
rent
(A)
0
0 Time (ms)
Volta
ge (k
V)
0
2000
–2000
10–10
–2000
2000
1000
–1000
20
Transients From Each Event Show the Same Reflections Suggest All Events Occurred at the
Same Location
Cur
rent
(A)
–0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6Time (ms)
–50
0
50
–50
0
50
Vol
tage
(kV
)
–0.2 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6Time (ms)
Reflection From Station 2
Reflection From Station 3
First and Second Events Triggered by Disconnect Closing; Third by Breaker Closing
Reactor Breaker
Disconnect
R
39.7 kmLine Trap
16.3 km 187.4 km
Station 1
Station 2 Station 3
Station 4
Cur
rent
(A)
0
0Time (ms)
200–200
2000
1000
–2000
–1000Closing disconnecttriggered a flurry of transients.Breaker closing produced clean transients.
• Lightning surges produce I0 only … no Iα or Iβ• We can locate lightning surges• Restriking launches waves in α and 0 modes• We can locate faults from the restrike waves• We can locate origin of high-voltage transients• Modes help us differentiate between lightning, faults,
restrikes, and incipient faults
MHz Sampling Reveals Details We Seldom See