Copyright © SDG&E, Quanta Technology, and SEL 2016
Catching Falling Conductors in Midair –Detecting and Tripping Broken
Distribution Circuit Conductors at Protection Speeds
Kirsten PetersenSan Diego Gas & Electric
• 22,000 miles of lines• 60% underground and 40% overhead• Grounded three- and four-wire systems • Nominally 12kV and 4kV• High penetration of distribution PV requires new solutions
for monitoring, protection, and control
SDG&E Distribution System
• Driven by high penetration of distribution PV• Voltage profile monitoring and control • Selective load shedding and restoration• Power quality monitoring • Apparatus and system condition monitoring• Falling conductor protection (patent pending)
Advanced SCADA Project ApplicationsMore Than 60 Use Cases Defined
• Increased accuracy of voltage and current • Phase angles from across circuit• GPS time-stamped data• 30 synchrophasor sets per second for fast measurement• IEC 61850 GOOSE messaging for real-time control• Remote engineering access and event reports• Advanced security features
Advanced SCADA Features
SCADA System ArchitectureTraditional
SCADA System ArchitectureAdvanced
SCADA System ArchitectureTraditional and Advanced Overlay
SDG&E Typical Feeder
R1
N.O.
R2
PV
Five-Way Switch
Capacitor Bank
CB
Line Monitor
Capacitor Bank
Capacitor Bank
Substation
Advanced SCADA Locations
To Control Centervia WAN
P P
P
P
P
P
P
P
N.O.
P
P
P
Line Monitor
VR4
R1
P
VR1VR2
PV11 MW
PV21 MW
S
DVC
Feeder Relay
69 kV/12 kV
R3
VR6
VR3
R5 VR5
R4
C3
C2
C1
P
Substation
PDC and Controller Switchyard
Fiber
LEGEND
P IED With PMU and Ethernet
R Recloser
WAN Wide-Area NetworkN.O. Normally Open
PV Photovoltaic
DVC Dynamic VAR Compensator
VR Voltage Regulator
S Multiport Circuit Switch
0
5
10
15
20
25
30
0.00 0.25 0.50 0.75 1.00 1.25
Con
duct
or H
eigh
t (ft)
Time (s)
Falling Conductor Timeline
0.5 s, 4 ft
1 s, 16 ft
Conductor hits ground at 1.37 s
Detect Broken Conductor and Trip Circuit Before Line Hits the Ground?
2 2dg
1d gt t22(30)t32.2
time 1.37s
Sequence Components Analysis
c1 b2
a2a1
b1 c2
a0
b0
c0
c2 2 a2c1 a1
b1 2 a1a0 b0 c0 b2 a2
Open-Phase Analysis
jXTG
ZL
jXTHG HZ1GHX Y
I1G I1H
Z1S
E
N1
jXTG
ZL
jXTHG HZ1GHX Y
I2G I2H
Z2S
N2
jXTG
G HZ0GHX Y
I0G I0H
N0
jXTH
Open-Phase Analysis
• dV/dt (change detection) • V0 and V2 magnitude• V0 and V2 angle
Detection Methods
dV/dt MethoddV0/dt Supervision CheckConductor Break
Between PMU 1 and PMU2
Trip PMU1
and PMU2
PMU1dV/dt
PMU2dV/dt
PMU3dV/dt
OR
PMU1 PMU2 PMU3dV0/dt
Between PMU 2 and PMU3
OR
Trip PMU2
and PMU3
X = threshold
> 0
< 0
< 0 < 0
< –X
> X
< X > X
> 0 > 0 < –X
> X
< X < X > X
< –X
> X
> X
dV0/dtdV0/dt
V2 and V0 Magnitude MethodConductor Break
V2 and V0 Angle Method
PMU1 PMU2 PMU3 PMU4
2 3 4
1
PMU1 PMU2 PMU3 PMU4
3 4
1 2
FC
1 not aligned with the other PMUs
1 and 2 aligned with each other3 and 4 aligned with each other
Source 1 Source 2
Source 1 Source 2
FC
is V2 or V0 angle
RTDS Feeder Model
Example Lab Test ResultsPV Off, Loop Open
Load % FC1 FC2 FC3 FC4100 3 3 3 375 3 3 3 325 3 3 3 3
PV On, Loop OpenLoad % PV% FC1 FC2 FC3 FC4
100
100 3 3 3 375 3 3 4 450 3 3 3 325 3 3 3 3
25
100 3 3 3 375 3 3 3 350 3 3 3 325 3 3 3 3
0
10
20
0–99 100–199 200–299 300–399 400–499
Arc Speed = 5 m/s
FC1 FC2 FC3 FC4(ms)
Arc Speed and Results ComparisonNumber of Test Cases Versus dV/dt Pickup Times
0
10
20
0–99 100–199 200–299 300–399 400–499
Arc Speed = 0 m/s
FC1 FC2 FC3 FC4(ms)
• Capacitor bank switching• Voltage regulator tap unbalance Angle method for ≈ 4.5% voltage (6 taps)
V0 magnitude method for ≈ 10% voltage (15 taps)
• Largest single-phase load switching• PV operation• Internal / external faults
Security Testing
ResultsDetection Screen
• Conductor break between PMU1 and PMU2
• PV inverter source ON
Inverter Response
ResultsdV/dt and Magnitude Methods
• First system installation in January 2015• Falling Conductor Protection (FCP) in
monitoring mode• Simulation of conductor breaks with
disconnect switch opening on recloser• 100% correct operation• Ethernet radio tuning required
Field Installation and Testing
Breaking Arc – Field Versus Lab TestsField Result RTDS Model
Falling Conductor Zones
CIRCUITBREAKER
RECLOSERRECLOSER
LINE MONITOR
TRAYER SWITCH
PV
VzVyVyVz
Vv
N.O.
SUBSTATION
Zone 1 Zone 2Zone 3Zone 4
LEGEND
PMU
VOLTAGE REG
VOLTAGE REG
Synchrophasors show detailed circuit behavior Capacitive voltage sensor discoveries
11 kV
6.8 kV
2.8 kV/s
–1.7 kV/s
0
577 V/s
– 400 V/s
0
Pha
seA
Vol
t age
dVA
/ dt
dV0/
dt
Load Side
Source SideNominal
6.9 kV
Time
Time
Time
dVA /dt > 1000 V/s
dV0 /dt > 400 V/s
Zone 1 dV/dt Operation
• Field Event – 28th Feb 2016• FC detected by dV/dt between CB and R1
Zone 1 Current Spikes
• Current spikes observed at CB and VR1, but not at VR2
• Indicates temporary fault between VR1 and VR2
RTDS Simulation
CIRCUITBREAKER
RECLOSERRECLOSER
LINE MONITOR
TRAYER SWITCH
PV
VzVyVyVz
Vv
N.O.
SUBSTATION
Zone 1 Zone 2Zone 3Zone 4
LEGEND
PMU
VOLTAGE REG
VOLTAGE REG
Simulated Disturbance in RTDS - Phase C- SLG Fault (High Resistance)- 0.01 seconds duration- Speculated High Impedance Fault
• Threshold based on RTDS testing results• dI0/dt spikes at CB PMU used to block falling
conductor detection algorithms• Temporary faults can be blocked using this
supervision
dI0/dt Supervision
Lab Simulation – Before dI0/dt
• Zone-1 mis-operation confirmed in lab
• dI0/dt block not implemented
• Mis-operation similar to field event
Lab Simulation – After dI0/dt
• Zone-1 mis-operation simulated in lab
• dI0/dt blocks Falling Conductor scheme
• System abnormal alarm condition
System Protection is a Balancing Act
• SPEED• SENSITIVITY
• SELECTIVITY• SECURITY
FAST TO MINIMIZE DAMAGE
RELAY SEES FAULT
DO NOT TRIP FALSELY
REMOVE FAULTED ELEMENT ONLY
• SIMPLICITY SIMPLE CONTROL SCHEMES
FCP Compliments Existing Layers of Protection• FCP – Falling Conductor Protection detects break in conductor Fastest – trips before the fault Coordination – FCP should be first
• Overcurrent – Time and Instantaneous Simple implementation
• SGF – Sensitive Ground Fault detects high-impedance ground fault Slow – 3.5 to 5.5 seconds Could Trip on Load
• Advanced SGF - More sensitive than SGF using adaptive set point, spike counting, and/or harmonics Slower – > 5 seconds Coordination between devices is unlikely
• Does not detect wire down without break• Needs fast Ethernet path to circuit PMUs• Uses voltage from each protected circuit path end – a
journey of years for coverage • Learning features of new technology
FCP Limitations
Ease of Application
• Key requirement achieved – no circuit-dependent application settings
• FCP logic only needs topology of circuit and PMU IEDs
To Control Centervia WAN
P P
P
P
P
P
P
P
N.O.
P
P
P
Line Monitor
VR4
R1
P
VR1VR2
PV11 MW
PV21 MW
S
DVC
Feeder Relay
69 kV/12 kV
R3
VR6
VR3
R5 VR5
R4
C3
C2
C1
P
Substation
PDC and Controller Switchyard
Fiber
• Advanced SCADA has 60 use cases including FCP• FCP isolates broken conductors in 0.2 – 0.5 s (half the
distance to the ground) preventing the fault• FCP is dependable in lab test including high PV penetration• FCP mitigates HILP events – fire and hazard reduction • Confidence built from secure and reliable field performance• Compliments existing protection• Scalable design needs only circuit layout information
Summary
• FCP of first equipped circuit commissioned on 11/18/2016• Additional circuits equipped and commissioned in 2017• Pursuing ongoing work to reduce fire risk and enhance
public safety• Installing new IEDs with PMU capable devices with
moderate additional cost• SDG&E will be well positioned for future PV penetration
Next Steps
Questions?