Post on 05-Jun-2018
Copyright © SEL 2017
Protection Challenges for North America’s First Combined Cable / Overhead
Double-Circuit 500 kV Transmission Line With Mutual Coupling
Denis Bucco, Curtis Sanden, Arturo Torres, and Edward Wong Southern California Edison
Jordan Bell, Normann Fischer, and John ThompsonSchweitzer Engineering Laboratories, Inc.
Copyright © SCE and SEL 2017
Project Background
• New 75-mile 500 kV transmission line• Single-circuit and double-circuit construction• Protection package System A – Line current differential
System B – Directional comparison blocking
System C – Permissive overreaching transfer trip
Decreasing Land Availability…
CSUSB WRI ©
© 2016 Google
From Overhead…
To Underground
TransitionTowers
East
West
Cable Layout
Vaults and Terminations
Overall Line Composition
Line Section 1: 33 Miles
• Two conductors per phase• Segmented ground wires
Line Section 2: 28 Miles
• Two conductors per phase• Segmented ground wires
Line Section 3: 4 Miles
• Underground• Two cables per phase
Line Section 4: 8 Miles
• Line 1: 500 kV line• Line 2: Future 500 kV line
Impedance Comparison
UndergroundZ1 = 0.02 + j0.31 = 0.31 ∠86° ohms / mile
Z0 = 0.20 + j0.13 = 0.24 ∠33° ohms / mile
OverheadZ1 = 0.05 + j0.58 = 0.58 ∠85° ohms / mile
Z0 = 0.44 + j2.13 = 2.17 ∠78° ohms / mile
IG ~ 0
Ground Wire Segmentation
• Phase conductors induce voltage in ground wire• Induced voltage leads to circulating current and losses
• Segmenting ground wires prevents circulating current
IG ≠ 0
Line Impedance Calculation
Where:
ZAA = Self impedance
ZAB and ZBC = Mutual impedance between phases
ZAA′, ZAB′, and ZAC′ = Mutual impedance between the A-phase conductor Line 1 and φ-phase conductor Line 2
VADROP = ZAA • IA + ZAB • IB + ZAC • IC + …ZAA′ • IA′ + ZAB′ • IB′ + ZAC′ • IC′
Put in Matrix Form…
VADROP
VBDROP
VCDROP
VAʹDROP
VBʹDROP
VCʹDROP
ZAA ZAB ZAC ZAAʹ ZABʹ ZACʹ
ZBA ZBB ZBC ZBAʹ ZBBʹ ZBCʹ
ZCA ZCB ZCC ZCAʹ ZCBʹ ZCCʹ
ZAʹA ZAʹB ZAʹC ZAʹAʹ ZAʹBʹ ZAʹCʹ
ZBʹA ZBʹB ZBʹC ZBʹAʹ ZBʹBʹ ZBʹCʹ
ZCʹA ZCʹB ZCʹC ZCʹAʹ ZCʹBʹ ZCʹC
IA
IB
IC
IAʹ
IBʹ
ICʹ
•=
…Then Sequence Domain
Z0 w x Z0M wm xm
w Z1 y wm z1m ym
x y Z2 xm ym z2m
Z0M wm xm Z0ʹ xʹ yʹ
wm z1m ym xʹ Z1ʹ zʹ
xm ym z2m yʹ zʹ Z2ʹ
=(Z012)
Line 1 Mutual
Mutual Line 2
Parallel Line Apparent Impedance
ZS_TERM = m • ZL1 (1 – ½ m)
ZT_TERM = ½ • ZL1 • (1 – m2)
Double-Circuit Apparent Impedance
0
2
4
6
8
10
0% 20% 40% 60% 80% 100%
Ohm
s Se
cond
ary
TheoreticalApparent
Sequence Impedance Through Energization
Positive-sequence Zero-sequence
Impedance Calculation
Matrix calculationZ1 = 3.26 + j33.32 Ω
Z0 = 24.73 + j142.65 Ω
EnergizationZ1 = 3.56 + j33.92 Ω
Z0 = 25.30 + j144.80 Ω
Charging Current Leads to High Voltage
Distributed capacitance charging current
Total charging current
Voltage rise
Charging Current Leads to High Voltage
≈ 2 amperes per mile overhead≈ 40 amperes per mile underground
Ph Ph1_CHRG 1
VI j C3−= ω
550
560
570
580
590
0 10 20 30 40 50 60 70
Volta
ge (k
V)
Line Distance (Miles)
Vincent
Protection System Validation
• Reduce short-circuit model to area of interest• Maintain 500 kV system with boundary equivalents• Build model in real-time digital simulator • Choose realistic operating conditions• Integrate physical relays with simulation
Protection System ValidationTest Plan
• Basic internal and external faults• Line energization and load pickup• Zone 1 margin• High-impedance faults• Batch tests
Batch Tests
• All internal and external fault locations (21 internal and 10 external)
• Ten fault types (AG, BG, CG, ABG, BCG, CAG, AB, BC, CA, and ABCG)
• Four fault inception angles (0, 30, 60, and 90 degrees)• All load flow cases
Distance Element Performance
0.0
2.0
4.0
6.0
4.5 3.3 2.2 1.1 0.0Mea
sure
d Im
peda
nce
(Ohm
s)
Theoretical Impedance (Ohms)
Mira Loma
0.0
2.0
4.0
6.0
0.0 1.5 3.0 4.5 6.0
Mea
sure
d Im
peda
nce
(Ohm
s)
Theoretical Impedance (Ohms)
Vincent
Zone 1 PerformanceManufacturer A
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100%
Ope
ratio
ns
Fault Location
Zone 1 PerformanceManufacturer A
Zone 1 PerformanceManufacturer A
3
3.5
4
4.5
5
5.5
6
6.13 6.50 6.88 7.25 7.63 8.00 8.38
Impe
danc
e (O
hms)
Time (Cycles)
Modify Settings and RepeatManufacturer A
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100%
Ope
ratio
ns
Fault Location
How Did the Other Relay Do?Manufacturer B
0%
20%
40%
60%
80%
100%
0% 20% 40% 60% 80% 100%
Ope
ratio
ns
Fault Location
Manufacturer A Distance Performance
0.0
0.8
1.5
2.3
3.0
0% 20% 40% 60% 80% 100%
Ope
ratin
g Ti
me
(Cyc
les)
Fault Location
Manufacturer B Distance Performance
0.0
0.8
1.5
2.3
3.0
0% 20% 40% 60% 80% 100%
Ope
ratin
g Ti
me
(Cyc
les)
Fault Location
Manufacturer B Differential Performance
0.0
0.8
1.5
2.3
3.0
0% 20% 40% 60% 80% 100%
Ope
ratin
g Ti
me
(Cyc
les)
Fault Location
Impedance-BasedFault LocatorManufacturer A
0.0
5.0
10.0
15.0
20.0
0.0 11.2 22.4 33.6 44.8 56.0 67.2Faul
t Loc
atio
n E
rror
(Mile
s)
Fault Location (Miles)
0.0
5.0
10.0
15.0
20.0
0.0 11.2 22.4 33.6 44.8 56.0 67.2Faul
t Loc
atio
n E
rror
(Mile
s)
Fault Location (Miles)
Traveling-Wave Fault Locator
• Explored to evaluate functionality on this composite line• Simulated in non-real time• Saved waveforms and replayed into the relays• Evaluated the relay response
Traveling-Wave Reflections
LL1, V1 LL2, V2 LL3, V3 LL4, V4
t0
t1
t2
t3t4
OpenClosed
IncidentReflectedJunction
Traveling-Wave Waveform
-5.0
-3.0
-1.0
1.0
3.0
5.0
Cur
rent
Mag
nitu
de(A
mpe
res
Seco
ndar
y)
Time (Cycles)
Traveling-Wave Measurements
-100
-60
-20
20
60
0 160 320 480 640 800 960 1,120
Trav
elin
g-W
ave
Mag
nitu
de
(Am
pere
s)
Time (Microseconds)
t0
t1
t2
t3 t4
Traveling-Wave Fault Locator Accuracy
-0.40
-0.20
0.00
0.20
0.40
0.60
0.00 18.67 37.34 56.01 74.68
Faul
t Loc
ator
Err
or
(Mile
s)
Line Length (Miles)
Summary
• Transmission line incorporated underground cables• Protection scheme needed reevaluation to include
multiple line current differential relays• Real-time digital simulation validated relay performance
Questions?