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Willem Boone, KEMA Diagnostic Services, Chalfont, PA ICC Fall 2000 Educational Program on PD Cable Diagnostics November PowerPoint Presentation
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Very Low Frequency Partial Discharge Detection; an Experienced Diagnostic tool for Distribution Cables. Willem Boone, KEMA Diagnostic Services, Chalfont, PA ICC Fall 2000 Educational Program on PD Cable Diagnostics November 1st 2000, St. Petersburg, Florida. Purpose of Diagnostic Testing

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slide1

Very Low Frequency PartialDischarge Detection; an Experienced Diagnostic tool for Distribution Cables

Willem Boone, KEMA Diagnostic Services, Chalfont, PA

ICC Fall 2000 Educational Program on PD Cable Diagnostics

November 1st 2000, St. Petersburg, Florida

slide2
Purpose of Diagnostic Testing
  • Principles of VLF testing Method
  • Test Results
  • Limitations and Innovative

Developments

  • Cost/Benefit Evaluations
  • Future Developments
  • Conclusions
maintenance options
MAINTENANCE OPTIONS
  • Reactive maintenance,

“wait-and-see”

  • Active maintenance,

“predictive maintenance”

reactive maintenance
REACTIVE MAINTENANCE
  • To repair or replace if something is broken
  • Short term view

(“no-health insurance”, “no-fire insurance”)

  • Short term benefit
active maintenance
ACTIVE MAINTENANCE
  • To avoid service failures
  • To specify network quality
  • To target replacement money
  • To improve customer satisfaction
  • To avoid customer claims
to transfer maintenance into predictive maintenance in order to reduce costs
TO TRANSFER “MAINTENANCE” INTO “PREDICTIVE MAINTENANCE” IN ORDER TO REDUCE COSTS
how to transfer maintenance into predictive maintenance
HOW TO TRANSFER MAINTENANCEINTO PREDICTIVE MAINTENANCE

Maintenance + diagnostic testing =

predictive maintenance

purpose of diagnostic testing
PURPOSE OF DIAGNOSTIC TESTING
  • To avoid failures in service
  • To reduce costs
  • To target replacement money
slide9
Principles of present

VLF diagnostic testing of cables

measurement setup

CABLE

0.1 Hz

HV- supply

PRINTER

SCOPE

PC

MEASUREMENT SETUP
characteristics vlf pdd
CHARACTERISTICS VLF PDD
  • Sine wave
  • Non-destructive
  • Off-lin
system parameters
SYSTEM PARAMETERS
  • Maximum voltage 41kV, RMS
  • 0,1 Hz, sine wave
  • Discharge-free
  • Maximum cable length to be tested 15,000 ft
  • All type of cable or accessory, however defect should generate P.D.
  • Non destructive test (maximum test voltage 2x phase-neutral voltage)
kema vlf pd testing applications
KEMA VLF PD TESTING APPLICATIONS
  • PILC
  • All kinds of accessories
  • Both point to point and branched cable circuits
  • Very long cable lengths
advantages of 0 1 hz power supply over 60 hz voltage
ADVANTAGES OF 0,1 Hz POWERSUPPLY OVER 60 Hz VOLTAGE
  • Longer lengths of cable to be tested
  • Compact voltage source
test results
TEST RESULTS
  • Test diagrams
  • Detected defects
  • Data base
recommendations
RECOMMENDATIONS
  • Replace/repair asap (<3 month)
  • Inspect asap
  • Retest (<2 year)
  • No action (retest < 5 year)
vlf pd database
VLF PD - DATABASE
  • A database application for storage and consulting measured data of MV-powercables
  • Data are used to diagnose cable system including splices and termination
  • Actual condition of cable and/or accessory can be predicted from the measured data stored
limitations of present vlf cable diagnostic testing
Limitations of present VLF cable diagnostic testing
  • Only straight cable connections
  • Only cable lengths up to 14,000 ft
slide29
Trials in te USA to Test

BCC-Diagnostics

  • September 1998
  • April 1999
slide30
Improvements After First Trial
  • Coupling to the Tested Cable
  • Master/Slave Unit
  • Digital Filter
slide31
Improvements After the

Second Trial

  • Software to Analyze Data
  • Remote Switching of Phases
kema diagnostic services

KEMA - Diagnostic Services

Branched Cable Testing

introduction
Introduction
  • General Test Procedure
  • Example Cable Map
  • Cable Tested Procedure
  • Results
  • Examples Taken From Actual Tests, In The USA, During The Past Year
general test procedure
General Test Procedure
  • Besides the 0.1 Hz voltage source used for the PTP testing, additional equipment is required such as a measuring node at each of the branches to be monitored. A node consist of:
      • GPS (Global Position System) Interface
      • Master-Slave Computer System
      • Communication Interface
  • Figure 1 is a schematic of a three-branched test set-up with one master node (#1) and two slave nodes (#2 and 3).
sample cable map example 1
Sample Cable Map Example #1
  • 5 Ended Distribution Cable
    • 4 Ends Have Cable Access
  • All Underground
  • Required 2 tests
included in test report
Included In Test Report
  • Maps As Shown
  • Text Describing “Zones”
  • Summary Table
sample cable map 2
Sample Cable Map #2
  • Multiple Ended Distribution Cable
    • 4 Ends Have Cable Access
  • All Underground
  • Required 3 Tests
results example 2
Results Example #2
  • The network was virtually divided into three Sections for the reporting purposes.
  • Test results and Mapping diagrams are presented individually for each Section.
included in test report46
Included In Test Report
  • Maps As Shown
  • Text Describing “Zones”
  • Summary Table
sample cable map 3
Sample Cable Map #3
  • Multiple Ended Distribution Cable
    • 2 Ends Had Cable Access
    • All Other Connections Required Utility To Cut Cable
  • All Underground
  • Required 4 Tests
  • Three Recording Nodes Were Used On Some Tests Sessions
results example 3
Results Example #3
  • The network was virtually divided into three Sections for the reporting purposes.
  • Test results and Mapping diagrams are presented individually for each Section.
included in test report58
Included In Test Report
  • Maps As Shown
  • Text Describing “Zones”
  • Summary Table
diagnostic testing
DIAGNOSTIC TESTING

Cost vs Benefit evaluation

factors to be considered

  • Cost of testing
  • Cost of repair of detected problem area(s)
waiting for failure
WAITING FOR FAILURE
  • Cost of failure locating
  • Cost of repair of failure
  • Cost of other damage initiated by failure
  • Cost of loss of revenue
  • Loss of customer satisfaction
diagnostic testing of distribution cable systems
DIAGNOSTIC TESTING OF DISTRIBUTION CABLE SYSTEMS

Utility tie to industrial customer in the Netherlands

Cable circuit 18.000 ft of 10 kV PILC cable installed in 1996

Problem three failures in three months

Proposed solutions

  • Replace 18,000 ft of cable
  • Perform or diagnostic testing
diagnostic testing of distribution cable systems63
DIAGNOSTIC TESTING OF DISTRIBUTION CABLE SYSTEMS

Cost (in NLG)

To replace the cable 1.800.000 NLG

Cost of diagnostic testing 8.000 NLG

Cost of replacing 2,500 ft

of cable 240.000 NLG

Saving by diagnostic testing 1.550.000 NLG

Percent savings: 86%

diagnostic testing of distribution cable systems64
DIAGNOSTIC TESTING OF DISTRIBUTION CABLE SYSTEMS

Industrial customer in the Netherlands

Cable circuit 35.000 ft of 10 kV PILC cable with 28 splices

Problem Six splice failures in three months

Proposed solutions

  • Replace all 28 splices

or

  • Diagnostic testing
diagnostic testing of distribution cable systems65
DIAGNOSTIC TESTING OF DISTRIBUTION CABLE SYSTEMS

Cost (in NLG)

Replace another 22 splices 110.000 NLG

Diagnostic testing 12.000 NLG

Replace 9 splices 45.000 NLG

Total cost of repair 57.000 NLG

Savings: 110.000 - 57.000 = 53.000 NLG

Percent savings: 48%

Added benefit:

Cable and 6 replaced splices tested OK

diagnostic testing of distribution cable systems66
DIAGNOSTIC TESTING OF DISTRIBUTION CABLE SYSTEMS

Preventive/predivtive maintenance diagnostic testing example from the Netherlands

The cable: 10 kV PILC, 105 circuits,

total of 500,000 ft

Cost of testing 420.000 NLG

Repair of 29 problems 145.000 NLG

Total cost of testing and repair 565.000 NLG

diagnostic testing of distribution cable systems67
DIAGNOSTIC TESTING OF DISTRIBUTION CABLE SYSTEMS

Wait for failure

Assume all 29 problem would fail in 1996

Fault locating cost (500 NLG ea.) 14.500 NLG

Repair cost (8.500 NLG ea.) 246.500 NLG

Customer damage cost

(20.000 NLG ea.) 580.000 NLG

Total cost 841.000 NLG

Total savings performing diagnostic testing

841.000 - 565.000= 276.000 NLG

Percent savings: 33%

diagnostic testing of distribution cable systems68
DIAGNOSTIC TESTING OF DISTRIBUTION CABLE SYSTEMS

Preliminary US cost benefit analysis

Based on data compiled by US utility, the cost

benefit ratio ranges from 1.5 to 1.9 based on actual

utility cost data

The assumptions include:

  • The circuits selected for testing have shown poor performance
  • The major discharge sites will fail within three years
  • The minor sites will fail within 20 years
new developments
New Developments
  • Multi terminal testing for long lenghts of cable and for branched circuits
  • Non-PDD testing for watertree aged cables
  • On-line testing using monitoring and expert systems
conclusions
Conclusions
  • VLF PDD is an experienced diagnostic method for distribution cable testing
  • Multi terminal testing is necessary for long lenghts of cable or branched cable circuits
  • Non-PDD field testing method has to be selected for detecting watertree aged cables
  • On-line testing has to be used in combination with monitoring/expert systems