Copyright © 2011. The Texas A&M University System. 1 Distribution Fault Anticipation (DFA) Technology John S. Bowers, PECarl L. Benner, PE Vice President

Copyright © 2011. The Texas A&M University System. 1

Distribution Fault Anticipation(DFA) Technology

John S. Bowers, PE Carl L. Benner, PEVice President of Operations Senior Research EngineerPickwick Electric Cooperative Dept. of Electrical and Computer EngineeringPO Box 49, 530 Mulberry Street 3128 TAMU, Texas A&M UniversitySelmer, TN 38375 College Station, TX 77843-3128731-646-3766 [email protected] [email protected]

DFA Technology Success Stories are available at:https://epridfa.tamu.edu/DFAReports/DFASuccess.aspx

Second Annual Smart Grid Research Consortium Conference:“Evaluating the Business Case for Smart Grid”

sponsored by Smart Grid ConsortiumOrlando, Florida, October 21, 2011


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.


Utility Partners

Hardware Demonstration SitesArizona Public ServiceBC HydroBryan Texas UtilitiesCenterPoint EnergyConEdisonCPS EnergyExelonKeySpan EnergyMidAmerican EnergyNortheast UtilitiesOmaha Public Power DistrictOncor Electric DeliverySouthern Company/Alabama PowerTVA/Pickwick Electric Cooperative

Other Previous/Current PartnersAmerican Electric PowerBaltimore Gas & Electric (Constellation)Central Hudson Gas & ElectricFirstEnergyPublic Service Electric & Gas


Conceptual Application of IntelligentAlgorithms to Electrical Waveforms

Intelligent Algorithms (Analytics)

Reliability

Condition-BasedMaintenance

Asset Management

ImprovedSafety

Outage Management

Forensics

Improved Power Quality

O&M Cost Reduction

Fault Anticipation Diagnosis of ProtectionProblems

Substation waveforms “know” about feeder activity. They can provide system awareness, if we measure them with sufficient fidelity and know how to interpret them.


Documented Failures•Voltage regulator failure•LTC controller maloperation•Repetitive overcurrent faults•Lightning arrester failures•Switch and clamp failures•Cable failures

– Main substation cable– URD primary cables– URD secondary cables– Overhead secondary cables

•Tree/vegetation contacts– Contacts with primary– Contacts with secondary

services

•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– Blown fuses– Switch restrike– Switch sticking– Switch burn-ups– Switch bounce– Pack failureCertain types of failures occur frequently and are well understood. Other types of

failures occur infrequently and only one or a few incidents have been documented. Ongoing field experience enables continuous improvement and next-generation DFA algorithms to diagnose those types of failures better.


We All Need More Data – Not!


On-LineSignal Processing

and PatternRecognitionAlgorithms

Performed byDFA device in

substation

Line recloser*tripped 8% ofphase-A load twice,but reclosed and didnot cause outage

Failed 1200 kVARline capacitor*(phase B inoperable)

Failing hot-lineclamp on phase B*

Inputs: Substation CT and PT Waveforms

*DFA system reports hydraulic reclosers, switched line capacitors, line apparatus failures, etc, based on substation waveforms, without requiring communications to those devices.

DFA ReportsDFA Algorithms


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.)


Waveforms are available for viewing and further analysis, if desired.

DFA Web-Based Reporting Format


UTILITY EXPERIENCE WITH DFAUtility Perspective


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


MYSTERIOUS SERVICE PROBLEM REQUIRES FOUR TRUCK ROLLS

Example


ExampleMysterious 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?


• For three weeks, the DFA system had been reporting a failing clamp on this phase of this circuit.…

• … but the dispatcher and crewwere unaware of the DFA report.

• This was a missed opportunity.Moving forward, providinginformation to right people canprovide awareness and ...

– Reduce complaints and truck rolls.– Reduce unnecessary equipment changeouts.

ExampleMysterious Service Problem


INCIPIENT FAILURES AND AVOIDABLE OUTAGES

Example


• 6/03/06 First fault; no outage• 6/10/06 Second fault; no outage• 6/17/06 Third fault; no outage• 6/24/06 Fourth fault; no outage• 6/28/066/28/06 Similar but unrelated Similar but unrelated

faultfault• 7/04/06 Fifth fault; no outage• 7/24/06 Sixth fault; outage

– 35 minutes, 903 customers– 31,605 CMI

6/03/06

6/10/06

7/24/06

ExampleAvoidable Outage – Without 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

ExampleAvoided Outage – With DFA


Step 1: Learn of recurrent fault from DFA DFA reported identical faults, 18 days apartStep 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 reclosersMomentary Load Interruption– DFA: Estimated 19-21% load interruption– Model: 23% of load is beyond RReclosing Interval– DFA: Reported 2-second open interval– Model: Reclosers at R have 2-second openConclusion: Failure is downstream of recloser R (26% of total feeder length).

Sub

R

Feeder NS 344(139 circuit miles)

Detailed ExampleAvoided Outage – With DFA


• 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).

REnlarged View of LineDownstream of R DBX

Sub

NS 344(139 circuit miles)

R

X


Sub

NS 344(139 circuit miles)

R

Enlarged View of Oval

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.


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.


FAULTY CAPACITOR CONTROLLER RESULTS IN EQUIPMENT DAMAGE AND DEGRADED POWER QUALITY

Example


ExampleCapacitor 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

Capacitor switching

events for one feeder

for one day!


ExampleCapacitor 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.


Feeder Lockouts Resulting from Protection Miscoordination(or Maybe Not!)

Example


ExampleImproper 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.)


ExampleImproper Breaker Lockouts


ExampleImproper 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.


Another Conductor-Slap Example9/

12/2

009

9/21

/200

9

Months0 0.3 5 19

2/11

/201

0

4/4/

2011

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

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.


INTERMITTENT FAILURE OF BREAKER TO RECLOSE RESULTS IN MULTIPLE SUSTAINED OUTAGES

Example


ExampleFeeder 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.


Examples:Other Anomalies

• Case 1: Line burned down past line recloser and auto-sectionalizer. 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.


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.


Benefit Estimates (Partial List)


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.


Contact Information

John S. Bowers, PE Carl L. Benner, PEVice President of Operations Senior Research EngineerPickwick Electric Cooperative Dept. of Electrical and Computer EngineeringPO Box 49, 530 Mulberry Street 3128 TAMU, Texas A&M UniversitySelmer, TN 38375 College Station, TX 77843-3128731-646-3766 [email protected] [email protected]

DFA Technology Success Stories are available at:https://epridfa.tamu.edu/DFAReports/DFASuccess.aspx

Documents

Copyright © 2011. The Texas A&M University System. 1 Distribution Fault Anticipation (DFA) Technology John S. Bowers, PECarl L. Benner, PE Vice President