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M i d Wi h d P i l Di hMonitored Withstand, Partial Discharge and Tan Delta Tests at Snohomish PUD

Ni l H t 1 J h P k l1 St St ik2Nigel Hampton1, Joshua Perkel1, Steve Stangvik21NEETRAC & 2Snohomish PUD

Spring 2012 ICC Meeting – Subcommittee FSeattle WA

Spring 2012 ICC Meeting Subcommittee F – Field Testing and Diagnostics

Seattle, WAMarch 27, 2012

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Part 1 Spring ICC: Testing &Part 1 Spring ICC: Testing & Asset Prognosis

Part 2 Fall ICC: Health Indices

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Snohomish PUD Cable System• Two areas tested

– Glenwood Mobile Homes (1976 & 1981 vintage)– Evergreen Shopping Center (1986 vintage)– Evergreen Shopping Center (1986 vintage)

• Homogeneous cable system– 15 kV voltage class (operated at 7.2 kV)– XLPE insulation– 1/0 conductor– Unjacketed concentric neutralj– Installed in conduit – no splices– Terminated with elbows

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Testing Sites

Glenwood Mobile Homes

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Evergreen Shopping Center

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Glenwood Mobile Estates

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Not your typical mobile home park

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Testing Approach

TDR

No Action Required

Action Required

Record&

CheckPD Test

Further

Tan δ RampAssessmentRecord

Study

Monitored

Record &

Check

Monitored WithstandPD or TD

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Testing Approach

TDR

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Testing Approach

TDR

Tan δ RampAssessment

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Tan δ - MV Test Protocol

Frequency

Features:• Stability @ 0.1 Hz & U0• Tip Up @ 0.1 Hz & between 1.5 U0 & 0.5 U0• Mean Tan δ @ 0.1 Hz & U0

Frequency[Hz]

0 10

Ramp Withstand

0.05

0.10

0.02

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Voltage[U0]

0.25 0.50 0.75 1.0 1.25 1.50 1.75 2.0 2.25 2.5

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Tan δ Criteria for PE-Based Insulation

ConditionAssessment

VLF-TD Stability(standard deviation)

at U0[10-3]

Differential TDTD 1.5 U0 – TD 0.5 U0

[10-3]

MeanVLF-TD

at U0[10-3][ ] [ ]

No No ActionAction

RequiredRequired(Best 80 %)(Best 80 %)

<0.05 & <5 & <4

0 05 5 4FurtherFurtherStudyStudy

0.05 to

0.5 Or

5 to 80 Or

4 to 50

ActionActionRequiredRequired

(W t 5 %)(W t 5 %)>0.5 >80 >50

(Worst 5 %)(Worst 5 %)

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Tan δ Overall (Tip Up & Stability)

1000.00Evergreen Shopping Center

0.05 0.5Glenwood Mobile Homes0.05 0.5

100.00

5Uo)

[E-

3]

80

10.00

1.00

Up (

1.5U

o -

0.5

5

0.10

0 01

Tip

U

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10.001.000.100.010.01

10.001.000.100.01TD Stability @ Uo [E-3]

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Tan δ Overall (Tip Up & Mean Tan δ)

1000.00Evergreen Shopping Center

4 50Glenwood Mobile Homes

4 50

100.00

5Uo)

[E-

3]

80

10.00

1.00

Up (

1.5U

o -

0.5

5

0.10

0 01

Tip

U

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100.010.01.00.10.01

100.010.01.00.1TD @ Uo [E-3]

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Basic Assessment Summary

Evergreen Glenwood

1986 Vintage12 Ckts

1976 & 1981 Vintage15 Ckts

Action Required13.3%

Further Study26.7%

No Action Required100.0%

No Action Required60.0%

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Testing Approach

TDR

2 Ckts20 Ckts

No Action Required

Action Required

Further

Tan δ RampAssessmentRecord

Record&

CheckPD Test

Study

Monitored

Record &

Check4 Ckts

Monitored WithstandPD or TD

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Example - No Action Required

1000

0 5[Uo]

VoltageTest

Tan δ StabilityTip Up

100

[E-3

]

0.51.01.5

Tip UpMean Tan δ

10

Tan

Del

ta [

1

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302520151050Measurement Sequence [#]

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Testing Approach

TDR

2 Ckts20 Ckts

No Action Required

Action Required

Further

Tan δ RampAssessmentRecord

Record&

CheckPD Test

Study

Monitored

Record &

Check4 Ckts

Record

Further StudyAction Required

PD Test

No Action Required

Failure

Monitored WithstandPD or TD

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Repair

Failure

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Example - Further Study

1000

0 5[Uo]

VoltageTest

Tan δ StabilityTip Up

100

[E-3

]

0.51.01.5

Tip UpMean Tan δ

10

Tan

Del

ta [

1

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Wet Circuits

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Monitored Withstand Criteria (PE)

ConditionAssessment

Change in Tan Delta between 0

d 10 i

VLF-TD Stability (standard

deviation) at M i t

Mean VLF-TD at

MaintenanceAssessment and 10 mins(E-3)

Maintenance Level [10-3]

Maintenance Level [10-3]

Reduce to 15 Mins <0.25 and <0.25 and <5

Extend to 60 Mins >17 or >6 or >45

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Monitored Withstand with Water?

[Uo]Voltage

Test

Stability@Uo = 0

Snopud Segment 6912

10

E-3]

0.51.01.5

[Uo]

Stability@1 5Uo 2 7E 3

TD@Uo=1.3Tip Up on Tip Up= 12.8Tip Up = 13.4Stability@Uo = 0

Tan

Del

ta [ Stability@1.5Uo=2.7E-3

1

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302520151050-5Test Time [min]

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0 to 10 mins

[Uo]Voltage

Test

Snopud Segment 6912

10

E-3]

0.51.01.52.2

[Uo]Difference between 10 & 0 mins= -4.5

Change in Tan Delta

between 0 and 10

mins

VLF-TD Stability

(standard deviation)

at Maintenance

Level

Mean VLF-TD at

Maintenance Level [10-3]

Tan

Del

ta [

E

(E-3) Level[10-3]

Reduce to15 Mins <0.25 <0.25 <5

1

Extend to60 Mins >17 >6 >45

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302520151050-5Test Time [min]

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0 to 30 mins

[U ]Voltage

Test

Snopud 6912

10

E-3]

0.51.01.52.2

[Uo]

Tan

Del

ta [

E

1

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302520151050-5Test Time [min]

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Final Classification - Retest1000

[Uo]_2Voltage

TestTan δ StabilityTip Up

100

[E-3

]

0.51.01.5

Tip UpMean Tan δ

10

Tan

Del

ta

1

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302520151050Measurement Sequence [#]

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Testing Approach

TDR

2 Ckts20 Ckts No PD

No Action Required

Action Required

Further

Tan δ RampAssessmentRecord

Record&

CheckPD Test

PD Detected

No PD

Study

Monitored

Record &

Check

4 Ckts2 Tested

Record

Further StudyAction Required

PD Test

No Action Required

Failure

Monitored WithstandPD or TD

2 Ckts

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Repair

Failure 2 Ckts

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Example – Action Required1000

0.5[Uo]

VoltageTest

Tan δ StabilityTip Up

100

[E-3

]

0.51.01.5

p pMean Tan δ

10

Tan

Del

ta

1

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VLF PDPh R l d PD P tt Ti F MPhase Resolved PD Pattern Time-Frequency Map

PD detected at 1.3 U0Analysis software classified discharge as “Internal”

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Testing Approach

TDR

20 Ckts 2 Ckts No PD1 Ckt

No Action Required

Action Required

Further

Tan δ RampAssessmentRecord

Record&

CheckPD Test

PD Detected

No PD

1 CktStudy

Monitored

Record &

Check

4 Ckts2 Tested

1 Ckt

Record

Further StudyAction Required

PD Test

No Action Required

Failure

Monitored WithstandPD or TD

2 Ckts

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Repair

Failure 2 Ckts

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What does this tell us looking forward• Single cable system design – cable only in conduit• Three vintages tested:

– 1976– 1976– 1981– 1986

• Each vintage has a different distribution of No Action Required, Further Study, and Action Required.

• Can try to predict the service performance and aging of these circuits as well as similar cables installed elsewhere in the system

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Time to Action Required Status

99

90

80

Action RequiredAssessment

99

90

80

Action RequiredAssessment

99

90

80

Action RequiredAssessment

8070605040

30[%]

8070605040

30[%]

8070605040

30[%]

20

10

Segm

ents

20

10

Segm

ents

20

10

Segm

ents

6.2%

17.5%

5

3

2

1

5

3

2

1

5

3

2

1

1.7%

25 30 35

Spring 2012 ICC Meeting Subcommittee F – Field Testing and Diagnostics

55504540353025201

Time in Service [Year]5550454035302520

1

Time in Service [Year]

29

55504540353025201

Time in Service [Year]

2 3 3

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Time to Further Study Status

99

90

80

Action RequiredFurther Study

Assessment99

90

80

Action RequiredFurther Study or Worse

Assessment99

90

80

Action RequiredFurther Study or Worse

Assessment99

90

80

Action RequiredFurther Study or Worse

Assessment99

90

80

93.2%Action RequiredFurther Study or Worse

Assessment

8070605040

30

nt

8070605040

30

nt

8070605040

30

nt

8070605040

30

nt

57.7%

8070605040

30

nt

39.3%

20

10

Perc

en 20

10

Perc

en 20

10

Perc

en

6.2%

20.6%20

10

Perc

en

6.2%

20.6%17.5%

20

10

Perc

en

5

3

2

1

5

3

2

1

5

3

2

1 30

5

3

2

1 25

1.7%

4.8%

30 35

5

3

2

1 40

Spring 2012 ICC Meeting Subcommittee F – Field Testing and Diagnostics

55504540353025201

Time in Service [Year]

30

55504540353025201

Time in Service [Year]5550454035302520

1

Time in Service [Year]

3

55504540353025201

Time in Service [Year]

2 3 3

55504540353025201

Time in Service [Year]

4

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Risk of Service Failures After Test30

20

%) 20

No Action RequiredFurther Study

Action Required

Overall Class

10

Insu

lati

ons

(

13

q

5

3 of

PE B

ased

6

2

1

Failu

res

5 Ye

ars

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100.010.01.00.11

Elasped Time Feb. 2011 (Month)

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Summary• Testing approach uses four diagnostic techniques: TDR,

VLF Tan δ, Monitored Withstand, and Offline PD.

• Targeted sampling of utility system can be used to establish current health of the system. – Need to sample enough circuits– Need a mixture of “good/bad” circuits

• In principle, diagnostic data and service performance d t b bi d t ti t f t f il tdata can be combined to estimate future failure rates.– Able to develop a plan of attack – circuits cannot be

deferred indefinitely.

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Part II – Health Indices

50 Stability 0Tip Up 614Tan Delta 2 3

VLF-TD Stability Differential TD Mean

0.50 1 2

Tan Delta 2.3

What is the classification ?ConditionAssessment

y(standard deviation)

at U0[10-3]

Differential TDTD 1.5 U0 – TD 0.5 U0

[10-3]

VLF-TDat U0[10-3]

No No

What is the classification ?

ActionActionRequiredRequired

<0.05 & <5 & <4

FurtherFurtherStudyStudy

0.05 to 0 5 O

5 to 80 O

4 to 50

Spring 2012 ICC Meeting Subcommittee F – Field Testing and Diagnostics

StudyStudy 0.5 Or 80 Or 50ActionAction

RequiredRequired >0.5 >80 >50

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