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© 2019 PNM and SEL
PNM Approach to Protecting Overcompensated High-Voltage Lines
Henry MoradiPublic Service Company of New Mexico
Kamal Garg, Mangapathirao V. Mynam, Eric Chua, and Jordan Bell
Schweitzer Engineering Laboratories, Inc.
• Overview of PNM system• Cabezon project summary• PNM protection standards• Series-compensated lines and protection challenges• PNM protection scheme• Laboratory tests and field events• Conclusion
Introduction
• 14,388 mi of transmission lines
• 69–230 kV primary voltage
• 46 kV subtransmission
• Large generation at San Juan, Four Corners substations
PNM System
115 kV230 kV345 kV
Rio PuercoCabezon
Four CornersSan Juan
HVDC Tie
HVDC Tie
SPP
Greenlee
Springerville
McKinley
• Compensation for Cabezon–Rio Puerco line is 170%
• Typical PNM compensation is 40–50%
• Shunt reactor provides reactive compensation
Cabezon Project Summary
Rio PuercoCabezonSan Juan
Four Corners
WW Linej63 Ω (109 mi)
CZ Linej19 Ω (34 mi)
FW Linej80 Ω (134 mi)
–j32.2 Ω
–j32.2 Ω
WW = San Juan–CabezonCZ = Cabezon–Rio PuercoFW = Four Corners–Rio Puerco
• Two relays at 115 kV and 230 kV and three relays at 345 kV
• Line current differential, POTT, and step-distance protection with backup overcurrent protection
• Quadrilateral distance protection for phase and ground Z1 = 70–80% of line impedance
Z2 = POTT forward direction, step-distance delay of 20 cycles
Z3 = POTT reverse direction
Z4 = Breaker failure, forward direction, delay of 60 cycles
PNM Line Protection Standards
• Backup instantaneous overcurrent element (phase and ground) at 15–20% of line
• Remote bus ground fault delay of 0.3–0.5 seconds • Three-pole tripping for most applications
PNM Line Protection Standards
115 kV Substation 1
115 kV Substation 2
Bus Protection Zone
115 kV Line With Tap Transformer
Transformer Protection Zone
• Differential protection uses positive-, negative-, and zero-sequence elements
• 115 kV lines use tapped load and do not use negative-sequence differential elements
• Future protection will include breakers at tapped substations, allowing system to be restored once transformer fault is cleared
PNM Line Protection Standards
86BF/CB3
86BF/CB2
86BF/CB186B/
B1–BCL CB1–BCL CB2–BCL All Bus 1 CBs
–BCL CB1–BCL CB2–BCL CB3
–BCL CB2–BCL CB3–BCL All Bus 2 CBs
Bus 1 Bus 2
Transformer 186T/T1
Line 1 Line 2
Line 3
CB1 BF (line and bus)1. Line 1 R1, R2, R32. Bus 1 RX1, RX2
Line R11. Re-Trip CB12. Trip CB23. DTT R2, R3 Line 14. TTR Remote End5. DTT RX1, RX2 Bus 16. Assert 86BF/CB1
Bus 1 R11. Re-Trip CB12. DTT RX2 Bus 13. DTT R1, R2, R3 Line 14. Assert 86BF/CB1
1 2 3
PNM Protection Standards
Shunt Reactor
UHS RelayIX IW
Shunt Reactor Reactor
Protection
87, REF, 50FB, 67Q
IS
IT
IY 1
Phasor-Based Relay
50BF, 21, 87
IX
IW
PNM Protection Standards
80
60
40
20
40 60
–20 Capacitor Bank Set = 4 kAFault Current Through Capacitor = 2.87 kAZ = 20.03 – 32.1 = ~–12.0 Ω
–20 20
Relay Response: Zone 2 Tripped. Delay = 0.33 s.B-C UNIT: Zone 2 Tripped.C-A UNIT: Zone 2 Tripped.A-B UNIT: Zone 2 Tripped.More details in TTY window.
FAULT DESCRIPTION:Bus Fault On: 0 RIO_PUERCO 345 kV 3LG
PHASE A0.0 + j –32.10.0 + j –32.1
PHASE B0.0 + j –32.10.0 + j –32.1
PHASE C0.0 + j –32.10.0 + j –32.1
EQUIVALENT IMPEDANCE OF MOV-PROTECTED SERIES CAPACITORS THAT FIRED [CHM]:
CAP PW 345.0kV – RIO_PUERTO 345.0kVCAP WW 345.0kV – RIO_PUERTO 345.0kV
–40
• Current and voltage inversion
• Impedance estimation
• Differential protection
Compensated Lines and
Challenges Rio PuercoCabezonSan Juan
Four Corners
WW Linej63 Ω (109 mi)
CZ Linej19 Ω (34 mi)
FW Linej80 Ω (134 mi)
–j32.2 Ω
–j32.2 Ω
WW = San Juan–CabezonCZ = Cabezon–Rio PuercoFW = Four Corners–Rio Puerco
Algorithm Phasors Incremental Quantities Traveling Waves
Signal spectrum of interest 40–70 Hz 0.5 kHz 100 kHz
Filtering
Sampling 16 s/c 10 kHz 1 MHz
Line theory VF = V – ZI
Operating time 1 cycle A few milliseconds 1–2 ms
Elements Z1P, Z1G, 32G, 32Q, and more TD21, TD32 TW87, TW32
Phasor and Time-Domain PrinciplesSimilarities and Differences
• Phasor-based protection
• Four quadrilateral zones
• POTT
• Line current differential settings Positive-sequence current = 600 A
Maximum line loading 1,004 MVA = 1,680 A (600 A / 2,000 A = 0.3 pu)
Zero-sequence element = 10–15% unbalance (10% • 2,000 = 200 A = 0.1 pu)
Negative-sequence element = 25% of 500 A = 0.25 pu
Reach Selection
• TD21 Phase and ground elements set to 75% and 70%,
respectively
External series compensation = Y
• TD32 TD32ZF = 0.3 • strongest impedance for fault at remote bus
TD32ZR = 0.3 • line impedance including series capacitor
Reach Selection – UHS Time Domain
• POTT – TP67P and TP67Gselected based on maximum incremental current caused by series capacitor switching
• TW87 – TP50P set above line charging current and below minimum remote bus fault current (select margin of 50–75%)
Reach Selection – UHS Time Domain
where:ZS1 = strongest local source impedanceZL1 = line impedanceZT1 = strongest equivalent remote source impedance
Rio Puerco
CabezonSan Juan
Four Corners
5–95% 5–95%
5–95%
5–95%
West Mesa
5–95%
B-A• Model system• Test internal and
external faults
Lab Testing
Line Percent (%)
Per
cent
(%) o
f Tot
al F
aults
0102030405060708090
100
• Phasor-based• Time domain
Lab Testing
Line Percent (%)
Per
cent
(%) o
f Tot
al F
aults
0102030405060708090
100Rio PuercoCabezon
Results Summary
10
16
12
1820
14
Ave
rage
Trip
Tim
e (m
s)
0
6
2
8
4
0Fault Location (% of line)
10 30 50 70 9020 40 60 80 100
Phasor-Based
UHS-Based
Rio PuercoCabezon
–400Vol
tage
(kV
)
Time (ms)–50 0 50 100
–2000
200400
TD32FKEY
PTRX
–4,0000
4,000C
urre
nt (A
)IC
IA IB
VCVA VB
External Faults –Cabezon
Date Fault Type Location
10/2/2018 CG Behind San Juan terminal
10/3/2018 CG Behind San Juan terminal
8/13/2018 CG Four Corners–Rio Puerco line
External Faults –CabezonΔ
Vol
tage
(V)
–100
0
100
TD32F
–20
0
20
Δ R
eplic
a C
urre
nt (A
)
–2 0 2 84 6 10Time (ms)
–2 0 2 84 6 10Time (ms)
Torq
ue (V
A)
–100–50
050
100150
Inte
grat
ed
Torq
ue (V
A)
–104–102
0102104
–2 0 2 84 6 10Time (ms)
–2 0 2 84 6 10Time (ms)
Operating
Operating
Forward Restraining
Reverse Restraining
Forward Restraining
Reverse Restraining
Time (ms)–20 20 400 60 80
PTRXKEY
TD32R
–400–200
0200400
Vol
tage
(kV
)–4,000
0
4,000
Cur
rent
(A)
–2,000
2,000 ICIA IB
VCVAVB
External Faults –Rio Puerco
Date Fault Type Location
10/2/2018 CG Behind San Juan terminal
10/3/2018 CG Behind San Juan terminal
8/13/2018 CG Four Corners–Rio Puerco line
Δ V
olta
ge (V
)
–100
0
150
TD32R
–20
0
15
Δ R
eplic
a C
urre
nt (A
)
–50
50100
–2 0 2 84 6 10Time (ms)
–2 0 2 84 6 10Time (ms)
–5
510
External Faults –Rio Puerco
Torq
ue (V
A)
–200–150–100
–500
50
Inte
grat
ed
Torq
ue (V
A)
–105
0
105
–2 0 2 84 6 10Time (ms)
–2 0 2 84 6 10Time (ms)
Operating
Operating
Forward Restraining
Forward Restraining
Reverse Restraining
Reverse Restraining
External Faults – 8/13/2018Rio Puerco End
ICWIBW
R32P67G3–400V
olta
ge (k
V)
–3,000
Cur
rent
(A)
0200400
0
2,000
Time (ms)500 100 150
3,000
VCYVAY VBY
–50
–200
1,000
–1,000–2,000
IAW
Time (ms)20 400 60 80 100
KEY67G2Z2G
–400
Vol
tage
(kV
)
–200
0
200
400–3,000–2,000–1,000
01,0002,0003,000
Cur
rent
(A) ICW
IAWIBW
VCYVAY VBYExternal Faults –8/13/2018
Cabezon End
• 170% series-compensated line
• Protection challenges for series-compensated lines
• Phasor- and UHS-based relays
• PNM protection standards and set point selection
• Laboratory tests to validate set points
• Phasor-based relay operating time ~16 ms, UHS relay operating time ~2–4 ms
• Field event analysis verifying performance
Conclusion
Questions?