Distribution Fault Anticipation
(DFA) Technology
Second Annual Smart Grid Research Consortium Conference:
“Evaluating the Business Case for Smart Grid”
sponsored by Smart Grid Consortium
Orlando, Florida, October 21, 2011
John S. Bowers, PE
Vice President of Operations
Pickwick Electric Cooperative
PO Box 49, 530 Mulberry Street
Selmer, TN 38375
731-646-3766
jbowers@pickwick-electric.com
Carl L. Benner, PE
Senior Research Engineer
Dept. of Electrical and Computer Engineering
3128 TAMU, Texas A&M University
College Station, TX 77843-3128
979-845-6224
carl.benner@tamu.edu
DFA Technology Success Stories are available at:
https://epridfa.tamu.edu/DFAReports/DFASuccess.aspx
Copyright © 2011. The Texas A&M University System.
1
Overview of DFA Technology
• Background: Technology’s foundation lies in EPRI’s DFA
(Distribution Fault Anticipation) project, performed by Texas
A&M, in close cooperation with multiple utilities. DFA label
persists for historical reasons.
• Substation-based DFA devices sense high-fidelity current
and voltage waveforms, using conventional CTs and PTs.
• DFA devices execute on-line algorithms that analyze
waveforms to diagnose failures, maloperations, etc.
• DFA system provides actionable reports about “important”
line activity.
• The result: Awareness of system conditions, including
incipient faults and outages.
Copyright © 2011. The Texas A&M University System.
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Utility Partners
Hardware Demonstration Sites
Arizona Public Service
BC Hydro
Bryan Texas Utilities
CenterPoint Energy
ConEdison
CPS Energy
Exelon
KeySpan Energy
MidAmerican Energy
Northeast Utilities
Omaha Public Power District
Oncor Electric Delivery
Southern Company/Alabama Power
TVA/Pickwick Electric Cooperative
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Other Previous/Current Partners
American Electric Power
Baltimore Gas & Electric (Constellation)
Central Hudson Gas & Electric
FirstEnergy
Public Service Electric & Gas
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Conceptual Application of Intelligent
Algorithms to Electrical Waveforms
Fault Anticipation
Diagnosis of
Protection
Problems
Condition-Based
Maintenance
Forensics
Asset Management
Intelligent Algorithms
(Analytics)
O&M Cost
Reduction
Improved Power Quality
Improved
Safety
Outage Management
Reliability
Substation waveforms “know” about feeder activity. They can
provide system awareness, if we measure them with sufficient
fidelity and know how to interpret them.
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Documented Failures
•Voltage regulator failure
•LTC controller maloperation
•Repetitive overcurrent faults
•Lightning arrester failures
•Switch and clamp failures
•Cable failures
•Pole-top xfmr bushing failure
•Pole-top xfmr winding failure
•URD padmount xfmr failure
•Bus capacitor bushing failure
•Capacitor problems
– Controller maloperation
– Failed capacitor cans
– Main substation cable
– Blown fuses
– URD primary cables
– Switch restrike
– URD secondary cables
– Switch sticking
– Overhead secondary cables
– Switch burn-ups
•Tree/vegetation contacts
– Switch bounce
–
Contacts
with
primary
Certain types of failures occur frequently and
well
understood. Other types of
– are
Pack
failure
– Contacts
with secondary
failures
occur infrequently
and only one or a few incidents have been
servicesOngoing field experience enables continuous improvement and
documented.
next-generation DFA algorithms to diagnose those types of failures better.
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We All Need More Data – Not!
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Inputs: Substation CT and PT Waveforms
DFA Algorithms
On-Line
Signal Processing
and Pattern
Recognition
Algorithms
Performed by
DFA device in
substation
DFA Reports
Line recloser*
tripped 8% of
phase-A load twice,
but reclosed and did
not cause outage
Failed 1200 kVAR
line capacitor*
(phase B inoperable)
Failing hot-line
clamp on phase B*
*DFA system reports hydraulic reclosers, switched
line capacitors, line apparatus failures, etc, based
on substation waveforms, without requiring
communications to those devices.
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DFA Web-Based Reporting Format
Reading Reported Protection Sequence (Hydraulic Line Recloser):
• Single-phase line recloser operated three times and locked out.
• Fault was phase-B and drew 745 amps.
• Sequence was fast-slow-slow (3 cycles, 12 cycles, 10-1/2 cycles).
• Open intervals were 2.1 and 2.4 seconds.
• Each operation temporarily interrupted half of phase-B load.
(Sequence of events below was created by DFA, not by humans.)
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DFA Web-Based Reporting Format
Waveforms are available
for viewing and further
analysis, if desired.
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9
Utility Perspective
UTILITY EXPERIENCE WITH DFA
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Pickwick Electric Cooperative
• Rural electric coop
 Headquartered in Selmer, Tennessee, home of Shiloh
National Military Park, Pickwick Dam, and Pickwick Lake
 Southwest corner of Tennessee, 100 miles east of Memphis
 Customer of Tennessee Valley Authority
 21,000 customers; 2,000 miles of distribution
• TVA’s participant in research behind DFA technology
 EPRI-funded project at Texas A&M
 Five feeders instrumented with DFA
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Example
MYSTERIOUS SERVICE PROBLEM
REQUIRES FOUR TRUCK ROLLS
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Example
Mysterious Service Problem
• T=0 hours: 16 customers with lights out
 Blown tap fuse, but no obvious system failure.
 New fuse holds. Close ticket.
• T=36 hours: Flickering lights in same area
 Crew hears buzzing transformer.
 Replace transformer. No buzzing. Close ticket.
• T=38 hours: Lights flickering again
Now what do I do?
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Example
Mysterious Service Problem
•
For three weeks, the DFA system had been reporting a
failing clamp on this phase of this circuit.…
•
… but the dispatcher and crew
were unaware of the DFA report.
This was a missed opportunity.
Moving forward, providing
information to right people can
provide awareness and ...
•
–
–
Reduce complaints and truck rolls.
Reduce unnecessary equipment changeouts.
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Example
INCIPIENT FAILURES AND AVOIDABLE
OUTAGES
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Example
Avoidable Outage – Without DFA
•
•
•
•
•
•
•
6/03/06
6/10/06
6/17/06
6/24/06
6/28/06
7/04/06
7/24/06
First fault; no outage
Second fault; no outage
Third fault; no outage
Fourth fault; no outage
Similar but unrelated fault
Fifth fault; no outage
Sixth fault; outage
6/03/06
6/10/06
7/24/06
– 35 minutes, 903 customers
– 31,605 CMI
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Example
Avoided Outage – With DFA
•Similar faults two days apart
•Next day
– Alerted by DFA
– Using DFA, found problem in 1 hr
– Avoided consequences
• Additional interruptions
• Extended outage
• Punch-through, moisture ingress
• Lid launch, burning oil, fire hazard
•7th day: Third fault prioritized repair
•No outage, complaints, or further consequences
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Detailed Example
Avoided Outage – With DFA
Feeder NS 344
(139 circuit miles)
R
Sub
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Step 1: Learn of recurrent fault from DFA
 DFA reported identical faults, 18 days apart
Step 2: Compare DFA info to system model at
various reclosers (e.g., recloser R)
 Protection
– DFA:
Reported operation of 1ø recloser
– Model: R is bank of 1ø hydraulic reclosers
 Momentary Load Interruption
– DFA:
Estimated 19-21% load interruption
– Model: 23% of load is beyond R
 Reclosing Interval
– DFA:
Reported 2-second open interval
– Model: Reclosers at R have 2-second open
 Conclusion: Failure is downstream of recloser R
(26% of total feeder length).
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R
Enlarged View of Line
Downstream of R
X
DB
•
Initial patrol downstream of R visually
identified cracked dead-end bells (DB),
but…
– DFA fault-current estimate @ DB: 510A
– Model fault-current estimate @ DB: 1086A
Then, using DFA fault-current estimate of
510A, model targeted area outlined in oval
(~2% of total feeder).
X
•
NS 344
(139 circuit miles)
R
Sub
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Enlarged View of Oval
NS 344
(139 circuit miles)
R
Sub
Manually integrating DFA information with system
model put failure in oval area, encompassing 4 spans
on either side of a tee. Searching that small area found
this failing arrestor. Replacing it avoided further
interruptions and likely outage to 53 customers.
Copyright © 2011. The Texas A&M University System.
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Recurrent Faults – A Recap
• DFA can detect failing apparatus and avoid outages.
– DFA often provides sole notice of problem. Without that, nothing else matters.
– Just counting faults on a feeder is insufficient. It is necessary to know that a
specific fault is recurring.
• Integrating DFA information with system model locates failure.
– For the subject case, this located failure within four spans, on feeder with total of
139 circuit miles.
– Process is straightforward, but manual application is tedious.
• Might it be feasible to automate the process of integrating DFA
information with a system model, to streamline the process of
learning of and locating these pre-failures? It would seem so.
• Important: This process locates failures that have not caused
outages and that often have not generated customer calls,
thereby making it feasible to avoid many outages.
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Example
FAULTY CAPACITOR CONTROLLER
RESULTS IN EQUIPMENT DAMAGE
AND DEGRADED POWER QUALITY
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Example
Capacitor Problem – Without DFA
• 1/2004: 28 cycles per day
• 2/2004: 100 cycles per day
• 2/29/2004-3/3/2004
 Switch contacts arced three days
 Severe voltage transients
 Failures in other cap banks
• Final consequences
 3,000 cycles in two months
 Failed switch
 Four damaged capacitor banks
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Example
Capacitor Problem – With DFA
• 8/9/2004
 Capacitor controller was changed
out during normal maintenance.
 Hours after crew left, controller
began switching bank continuously.
• 8/10/2004
 DFA reported 22 switching events.
 Crew corrected controller settings.
 Continuous switching stopped.
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Example
Feeder Lockouts Resulting from
Protection Miscoordination
(or Maybe Not!)
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Example
Improper Breaker Lockouts
• Remote fault tripped mid-point line recloser, but
breaker tripped, too, locking out feeder.
• Utility performed lengthy investigation.
Result: “Cause Unknown.”
• Two years later, same thing happened again.
• This time, the DFA system helped utility to identify
and locate fault-induced conductor slap (FICS).
• (FICS: Distant fault trips mid-point recloser, but
magnetic forces cause close-in wires to swing
together, creating second fault.)
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Example
Improper Breaker Lockouts
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Example
Improper Breaker Lockouts
• DFA reports conductor-slap and enables location.
• Result: Utility can alter the offending line segment, thereby
preventing future breaker operations and feeder lockouts.
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Another Conductor-Slap Example
0 0.3
5
Facts (this case):
• Four conductor-slap incidents
• Eight unnecessary breaker trips
• Same location on same feeder
• Breaker tripped two times for each event
• Phenomenon was not discovered by
conventional tools available to utilities
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Months
Ramifications (in general):
• Conductor-slap and fault will recur in future.
• Progressive conductor damage, with possibility of
conductor burn-down
• Stress on all current-carrying components
(switches, connectors, …)
• Fire hazard from burning aluminum particles
A significant finding has been that slap does not happen at random locations on feeders.
Locations experiencing slap once, left uncorrected, likely will experience it again and again,
repeatedly creating system stresses and the chance of prolonged outages, fire, etc.
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Example
INTERMITTENT FAILURE OF BREAKER
TO RECLOSE RESULTS IN MULTIPLE
SUSTAINED OUTAGES
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Example
Feeder Breaker Fails to Reclose
•
•
•
•
•
•
•
•
04/08/10: Breaker operates properly.
08/06/10: Breaker operates properly.
10/19/10: Breaker fails to auto-reclose.
12/10*: Standard tests show no problem.
01/08/11: Breaker fails to auto-reclose.
03/06/11: Breaker operates properly.
03/18/11: Breaker fails to auto-reclose.
03/26/11: Breaker operates properly.
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Examples:
Other Anomalies
• Case 1: Line burned down past line recloser and autosectionalizer. DFA helped determine which device failed.
• Case 2: In multiple cases, utility has used DFA to determine
whether questionable reclosers were functioning properly,
without removing them for offline testing.
• Case 3: DFA report is helping ongoing investigation to diagnose
why a self-healing circuit did not respond properly.
• Case 4: DFA helped utility identify that a three-phase recloser had
stopped mid-sequence, failing to reclose or lock out, creating
hazard for a crew that assumes open recloser is locked out.
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Possible Future Algorithms
• Continual process of discovering new signatures and
expanding capabilities is inherent in DFA technology’s
future roadmap.
• Fundamental design of system anticipates and
accommodates future extensions of capabilities.
• For example, Texas A&M currently is evaluating potential
unique characteristics for…
– Lightning-induced faults.
– Arrester-induced faults.
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33
Benefit Estimates (Partial List)
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Conclusions
• DFA technology provides advanced on-line diagnostics,
creating awareness we never had before.
• We are dealing with new types of information, not
previously envisioned. New processes and procedures
may be required.
• Utilities are using DFA to avoid outages and better
diagnose other problems, but need better access to
reports to enable them to take full advantage.
• New EPRI project is addressing issues regarding when
and how to deliver information, for best use and impact.
• Field installations continue to provide data for discovery
of new “fingerprints” and better diagnosis and reporting.
Copyright © 2011. The Texas A&M University System.
35
Contact Information
John S. Bowers, PE
Vice President of Operations
Pickwick Electric Cooperative
PO Box 49, 530 Mulberry Street
Selmer, TN 38375
731-646-3766
jbowers@pickwick-electric.com
Carl L. Benner, PE
Senior Research Engineer
Dept. of Electrical and Computer Engineering
3128 TAMU, Texas A&M University
College Station, TX 77843-3128
979-845-6224
carl.benner@tamu.edu
DFA Technology Success Stories are available at:
https://epridfa.tamu.edu/DFAReports/DFASuccess.aspx
Copyright © 2011. The Texas A&M University System.
36