PJM 20/20
TRANSMISSION TECHNOLOGIES
Geomagnetic Disturbances (GMD)
PJM Valley Forge, PA
April 17, 2013
Emanuel Bernabeu, Ph.D.
Agenda
•
•
•
•
GMD Overview.
Dominion’s Mitigation Methodology.
Modeling GIC Flows.
Operational Procedures.
–
Situational Awareness.
Introduction: Geomagnetically Induced
Currents (GIC)
Ionospheric
Electrojet
Grounded
Transformer
Transmission Grounded
Line
Transformer
E
GIC flow
GIC
GIC
Ex t
t
1
0
Ey t
t
1
0
1
By t
t u
t
du
Bx t
du
t
t u
1
Introduction: Transformer ½ Cycle Saturation
• Geomagnetically Induced Current (GIC): Quasi-DC: <0.1Hz.
• Transformer ½ cycle saturation:
–
–
–
Hot-spots
MVARs
Harmonics
transformer damage.
voltage stability.
system protection.
capacitor banks.
generators.
B
DC shift
Time
I
Imac+dc
Time
Introduction: Large GMD Events
• Hydro-Quebec Blackout 1989:
–
–
–
–
7 SVCs tripped.
Voltage Collapse in 90 seconds
Transformer consume more MVARs.
Loss of 21,500 MW of generation.
1 confirmed transformer damage: Salem’s GSU
• Halloween Storm 2003:
–
Outages in Sweden.
• Carrington event 1859:
–
Largest earth-directed “observed” CME.
GMD Impacts at Dominion
• Impact at Dominion:
–
–
Several capacitor bank trips:
1989, 1990, 1991, 2001, 2002,
2004.
No other major impact.
Substation
NN
NN
NN
NN
NN
NN
NN
NN
kV
230
230
230
230
230
230
230
230
Substation
NN
NN
NN
NN
NN
NN
NN
kV
115
230
230
230
230
230
115
500 kV
230 kV
115 kV
Dulles
Idylwood
Loudoun
Ox
Valley
Elmont
Stauton
Dooms
Chickahominy
Midlothian
Va Beach
Carson
Chuckatuck
Yadkin
Fentress
Dominion’s GMD Mitigation Methodology
• Cost effective methodology:
–
–
Balancing the “fortress” approach vs. operational mitigation.
Ongoing effort since 1989.
• Three pillars:
–
–
–
Modeling.
Equipment hardening.
Operational procedures.
GIC
Model
System
Operations
Situational
Equipment
Awareness
Hardening
Equipment Hardening
• Transformers:
–
–
–
GIC specification (~40%).
Comprehensive spare plan and logistics.
Monitoring: GIC, DGA, Harmonics, Hot-spots.
• Capacitor banks:
–
–
Oversized for harmonics and voltage.
Unbalance protection
Voltage differential per phase.
• SVCs:
–
Technical specification: protection, harmonic filters, controls,
transformer, etc.
• No GIC blocking devices.
Modeling GIC in Power Systems
• Objective:
–
–
–
Determine critical locations in the system.
Develop operation guidelines.
Voltage stability: estimate impact of MVAR requirements.
• Methodology:
Estimate Geo-Electric
Field
DC Network
Model
9
GIC Flows
System
Operation
Step 2: Network DC model
• DC-mapping of the transmission network
Transmission
Line
Rline /3
RTX /3
GSU
Re
500 kV
Auto Transformer
Rseries /3
230 kV
Virtual node
Re = Inf
10
Rcommon /3
Re
Step 2: Example
Bus B 500 kV
Bus A 500 kV
RLINE
XLLINE
GSU
TX1
Power System
Bus B 230kV
Δ Y
DC - Mapping
Bus B 500
Bus A 500
GIC Model
VAB
RLine
Re=Inf
RGSU
Re, A
Bus B 230
RTX1, Series
RTX1, Common
Re, C
11
Step 3: Solution Engine (Matlab)
Lat, Long 2 X,Y
Vij
Busi
E ds
Iij
Sij
ΔV
Yij
Y Y
ii
Ze
Ie,i
U Y Ze
Y
I ji
J ij
1
Z e,ii I e,i
N I S IC
N 1
I AutoTx
12
Je
Ze,jj
J e ,i
J ji
j i
Z e, jj I e, j
Rij
GIC flows
MVar, Harmonics
Ie,j
Zij 0 or Re,i
Zii Re,i parallel RTx ,i
Ie
Busj
Ze,ii
k
Ze
Vij
Rij
yik
Eq. parallel lines
Virtual lines Auto-Tx
yij
N
VH
VL
1
J ji
V ji
R ji
MATLAB Simulation
• |E|=2 V/km.
• Model:
–
–
–
497 buses.
511 transmission lines.
230 transformers.
• GIC is a function of:
–
–
–
–
Topology.
Transformer type.
Grounding resistance.
Line/Tx resistance.
500 kV
230 kV
115 kV
Critical Locations
• Critical Locations: sites prone to larger GIC.
–
–
Monitoring sites.
Further system studies.
From
NN
NN
NN
NN
NN
NN
NN
NN
NN
NN
NN
NN
To
NN
NN
NN
NN
NN
NN
NN
NN
NN
NN
NN
NN
Avg GIC
59
57
41
40
33
31
23
22
21
19
16
15
Non-Uniform Geo-electric Fields
• Non-uniformity is represented
by partially uniform E.
–
Vij is independent of the path
of integration within partially
uniform E.
• The rest of the GIC calculation
program remains unchanged.
• Critical for large models (RTOs).
Uniform geoelectric field
Winding Hot-Spot
Winding Hot-Spot
Temperature [Degrees] Temperature [Degrees]
85
30
65
45
-20
65
-70
105
30
85
-20
-70
GIC [Amps/pahse]
105
GIC [Amps/pahse]
45
1
60
119
178
237
296
355
414
473
532
591
650
709
768
827
886
945
1004
1063
1122
1181
1240
1299
1358
1417
1476
1535
1594
1653
1712
1771
1830
1889
1948
2007
2066
2125
–
–
1
7
13
19
25
31
37
43
49
55
61
67
73
79
85
91
97
103
109
115
121
127
133
139
145
151
157
163
169
175
181
187
193
199
System Operation Challenges During GMD
• Risks posed by GMD have two time horizons:
Long term: transformer hot-spots.
Short term: voltage stability (harmonics).
Temperature
GIC
Time [minutes]
Temperature
GIC
Time [minutes]
Operating Guidelines
• Two objectives:
–
–
Prevent critical equipment damage.
Prevent a blackout.
• Operating procedures:
–
–
–
–
–
–
–
–
Re-dispatch (PJM).
Topology changes: switching out lines/transformers.
Transformer cooling.
Cancel outages on reactive support equipment.
Ensure series compensation is in service.
Study switching out/in reactor banks.
Special contingency studies.
Monitor reactive power reserves.
17
Switching out a Transformer
• In general, switching out a transformer increases GIC at other
transformers.
Impact is a function of topology.
Parallel transformers experience largest increase.
∑(∆GICTX) [Amps per phase]
–
–
60
50
40
30
20
10
0
-10
-20
1
4
7
10 13 16 19 22 25 28 31 34 37 40 43 46
Transformer Switched
|E| @ 0 Degrees
|E| @ 90 Degrees
18
Switching out a Transmission Line
∑(∆GICLN) [A /phase]
∑(∆GICTX) [A /phase]
GIC in Transformers
GIC in Lines
• In general, switching out a line decreases overall GIC flow.
0
-100
-200
-300
1
4
7
10 13 16 19 22 25 28 31 34 37 40 43
Transmission Line Switched
1
4
7
10 13 16 19 22 25 28 31 34 37 40 43
200
100
0
-100
-200
-300
Transmission Line Switched
19
Switching out a
transmission line can
increase the GIC flow
at certain transformers
Example: Line 36
• Two substations become “edges” of the system.
Line #36
Switched Out
|E| = 2 V/Km
+∆ 25[A/phase]
+∆ 26[A/phase]
+∆ 52[A/phase]
500 kV
20
Example: Line 18
• Resistance to GIC flow increases.
500 kV
|E| = 2 V/Km
-∆ 28[A/phase]
-∆ 20[A/phase]
-∆ 33[A/phase]
Line #18
Switched Out
-∆ 30[A/phase]
-∆ 51[A/phase]
-∆ 60[A/phase]
Situational Awareness: GIC-net
• Real Time:
–
–
Real-time GIC monitors.
Transformer monitoring:
• Harmonics (2nd from 87).
• DGA.
• Excess MVAR (future).
–
–
–
Capacitor bank harmonics monitoring.
Magnetometer (future).
GIC flows calculations (future – SWA)
• GMD forecast.
–
–
NOAA (current).
SWA (future).
GIC
Magnetometer
Conclusion
• Risks posed by GMD have two time horizons.
• Optimal balance: equipment hardening & operational
mitigation.
• Successful implementation of operational mitigation requires:
–
–
–
Sharing actionable data between BAs and PJM.
Accurate system model and system studies.
Asset risk assessment.
Future Planned PMU
Installations to be
incorporated into
system developed
under this grant.
Questions?