Field Applications and experiences on UHF PD diagnostic technology for 765 kV GIS

IERE GM 2008(November 17~20, 2008 - Brazil)

Kijun Park and Kisun HanPower System Laboratories

Korea Electric Power Research Institute - KEPCO65 Munji-ro, Yuseong-gu, Daejeon, 305-380, Rep. of KOREA

Tel: +82-42-865-5864E-mail: killer@kepri.re.kr

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Contents

1. Technical Background- Introduction- UHF PD detection technology- Sensors, optimal placement- Diagnostics system

2. Applications and Experiences- Example of field experiences- Summary

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UHF PD diagnosis for GIS:

Technical Background

Why PD detection is important in GIS?

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Loss of Insulation

PARTIAL DISCHARGE

Aging BreakdownBreakdown

Conduction loss

Particles

Melt, ArcHeat

Decrease in Insulation

Decrease gas densityGas leak

Switching SurgeLightning Surge

The Gas-insulated switchgears

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Compact in sizeCompact in sizeHigher capacityHigher capacityMaintenance Free design Maintenance Free design Hard to know Internal Hard to know Internal

defectsdefectsFaults affect wider areaFaults affect wider areaLoss of huge $$$Loss of huge $$$

Need a Need a Diagnosis ToolDiagnosis Tool

UHF PD detection technology

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0 25 50 75 100

-60

-30

0

30

60

PD

Sig

nals

(mV

)

Time (ns)-2 -1 0 1 2 3 4

0

40

80

120

160

Dis

char

ge C

urre

nt (m

A)

Time (ns)

PD source- Protrusion (Corona)- Free particle- Floating electrode- Void, insulation defect

PD source- Protrusion (Corona)- Free particle- Floating electrode- Void, insulation defect

EM wave propagation- Attenuation- Reflection- Mode- Noise, interference

EM wave propagation- Attenuation- Reflection- Mode- Noise, interference

Various analysis- PRPD/PRPS- Trend- Noise rejection- Pattern analysis

Various analysis- PRPD/PRPS- Trend- Noise rejection- Pattern analysis

Various PD measurement methods for GIS

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UHF PD diagnostic systems for 765 kV substations

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On-line PD diagnostic system

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Sensors

Network

Data Acq.Hardware

AnalysisSoftware

Various UHF PD sensors (154~765 kV GIS)

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Internal type

External type

UHF PD sensor specification

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**For comparison and test procedure typical output of sensor is specified for discharge of 5 pC at 1 m.

UHF PD propagation loss in GIS

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Typical propagation loss: 765 kV GIS, 500-1500 MHzTypical propagation loss: 765 kV GIS, 500-1500 MHz

Sensor A Sensor CSensor B

Network Ana lyzer

Pb Pc

Attenuation(A dB)= 10Log (kP

b c

b

,10 /kP )

= 10Log (P /P )c

b c10

kPb kPc

M

kPb

Optimal placement of PD sensor

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765 kV GIS

External noise shielding

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Ni type shielding tapesNi type shielding tapesNi type shielding tapes

Au-type shielding tapesAuAu--type shielding tapestype shielding tapes Shielding bandsShielding bandsShielding bands

Data acquisition units

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Connection to the sensors Signal processing (amplification, filtering,

etc.)Digital conversion of signalNetwork connection to the host computer

Connection to the sensors Connection to the sensors Signal processing (amplification, filtering, Signal processing (amplification, filtering,

etc.)etc.)Digital conversion of signalDigital conversion of signalNetwork connection to the host computerNetwork connection to the host computer

Monitoring system specification

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UHF PD diagnostics at KEPCO

• Use of on-line monitoring systems for GIS– First introduced in 1998– Expanded from 2004~

• All 765 kV Substations, Major 345 kV substations• Switchyard of major power plants

– Use of external- or internal-type sensors – Optimal positioning of sensors, specifications– Internal-type UHF PD sensors for all new GIS installation

• Use of portable PD monitoring devices– Retrofit of internal sensors for all 154 kV GIS– Internal-type UHF PD sensors for new GIS installation– Scheduled inspection using portable type PD diagnostic

devices– UHF PD test at commissioning for all newly installed GIS

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Field applications and experiences

Floating electrode: loose bolt

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Floating electrode: loose bolt (cont)

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Free particle in CB

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Floating electrode in CB

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Floating electrode in CB (cont)

PRPD: Floating electrodePRPD: Floating electrodePRPD: Floating electrode

Clean-up &Exchange parts

CleanClean--up &up &Exchange partsExchange parts

PD signal disappearedPD PD signal disappearedsignal disappeared

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Free particle in DS compartment

Arrival time differenceArrival time differenceArrival time difference

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Free particle in DS compartment (cont)

0 1 2 3 4 5 6 7 8

125

250

375

500

625

750

875

1000

400 sec.12,062 times PDs

PD A

mpl

itude

(m

V)

PD Pulse Intervel (Cycle)

0.5000

1.500

2.500

3.500

PRPDPRPDPRPD Vn : (tn – tn-1): NVVnn : (: (ttnn –– ttnn--11): N): N25

Commissioning test: AC voltage (362 kV GIS)

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Sensors

10 5 1 (min)

Voltage

Summary: GIS PD diagnostics

• Many cases of PD diagnostics and problem isolation• KEPRI conduct many intensive diagnostics• Prevent loss of multi-million $$ • Ensures quality of power delivery

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Floating electrode

42%

Voids29%

Free particle

8%

Noise, etc.21%

0

1

2

3

4

5

2000 2002 2003 2004 2005 2006 2007 2008

Floating electrode Voids Free particle Noise, etc.

SUMMARY

• UHF PD diagnostics for GIS– Well developed technology

– Online systems: GIS in 765 kV, major 345 kV, Power plants

– Portable type inspection: All other GIS

– Use of internal sensors for new installation

– Use of UHF PD monitorign at commissioning tests

– Intensive diagnostics: Locate and verify internal defects

– Various diagnostic cases : Prevent failures, Save time and cost!

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Thank you!