jicable11, 19 - 23 june 2011 - versailles - france modern methods of installation and diagnostic...

Jicable’11, 19 - 23 June 2011 - Versailles - France

MODERN METHODS OF INSTALLATION AND DIAGNOSTIC TESTING

OF DISTRIBUTION POWER CABLES

Edward GULSKI, onsite.hv.solutions, Switzerland Frank DE VRIES, Alliander, The Netherlands

Piotr CICHECKI,, onsite.hv.solutions Benelux, The Netherlands Johan J. SMIT, TU Delft, The Netherlands


CONTENT

• Introduction• Testing with DAC (OWTS)• Standards and knowledge rules for after installation tests• Standards and knowledge rules for diagnostic tests• Practical example• Conclusions• Future steps


INTRODUCTION

• Biggest DSO in the Netherlands• Over 35000km MV cable circuits• MV levels: 6, 10, 20 and 50kV• 15 years experience in PD

measurements on MV cables• 3 teams specialists• Over the last 10 years more than

3500 cables have been diagnosed with DAC


TEST PRINCIPLE OF DAC (OWTS)

L C cable

wifi

Computer

U & PD

Solid state switch

HV

Sou

rce


PD MEASUREMENT WITH DAC (OWTS)

Testvoltage

PD activity


IMPORTANT PARAMETERS• PD inception voltage (PDiV)• PD extinction voltage (PDeV)• PD level @ Uo• PD level vs Testvoltage• Phase resolve pattern• PD location


STANDARDS FOR AFTER INSTALLATION TESTSON NEW CABLES

• Based on NEN3620

– Voltage Withstand Test cablesheath

• 5kVDC-5 min

– Voltage Withstand Test main insulation

• 3xUo, 0,1Hz-15min or• 50 cycles 3xUo DAC

– PD measurements• 0,25-0,5-0,75.....2xUo

• Voltage withstand tests– Simple rule accepted / rejected– Destructive method– Not monitored

• PD measurements– Monitored test method– Gives information about abnormalities– Interpretation of results is complex

Alliander:All new cablecircuits are tested according NEN3620 also PD measurement are performed on new cable circuits that include joints


PDiV < 1,7xUo

Rejected Accepted

PDiV > 1,7xUo

Decision process for PD testing with DACAfter laying testing of new Cable circuits: XLPE insulation


PDiV < 1,2xUo

Rejected Accepted

1,2xUo < PDiV < 1,7xUo PDiV > 1,7xUo

PD intensity> 3 per cycle ?

no

yes

Decision process for PD testing with DACAfter laying testing of new Cable circuits: Cable joints

PD magnitude> 100pC ?

no

yesno

Repetition of test possible?

yes

Test repetition


COMPANY STANDARDS FOR DIAGNOSTIC TESTSON AGED CABLES

• For XLPE cable circuits– Voltage Withstand Test on

cable sheath • 5kVDC-5 min

– PD measurements • up to 2xUo*

• For PILC circuits– PD measurements

• up to 2xUo*

– TanD measurements • up to 2xUo*

– Voltage withstand test• with DC 2xUo√2* 5

minutes, • VLF 2xUo* 5 minutes or• DAC 2xUo* 50 cycles

* Or lower testvoltage in case of safety aspects

Alliander:Only suspicious cablecircuits are diagnosed.

* Or lower testvoltage in case of safety aspects


DEVELOPMENT OF KNOWLEDGE RULES FOR DIAGNOSTIC TESTS

Knowledge rules

-Statistics-Component investigations

-Determination-Statistic boundaries

-Physics of PD processes -Component properties (design and materials)-Operation parameters

-Escalation (destructive tests)-Fundamental tests-Behaviour of different PD types

Predict

Theoreticalinformation

Test

Laboratory tests

Evidence

Failure information

Detect

Measurementdata


PRACTICAL EXAMPLE PD activity in a joint

Cable circuit in Alkmaar area: - 10kV PILC 3x95Cu and 3x150AL- 4 joints (different types of oil joints)

Interruption caused by external damage.After repairing the failure the cable sometimes broke down at 1,5Uo during the DC voltage test. Localisation of breakdown was difficult.

We applied PD measurement on the cable to detect the problem.

Joint 1: 260m

Joint 2: 310m

Joint 3: 650m

Joint 4: 700m

1100m


PRACTICAL EXAMPLE Advise and taken action

Failure information

Measurementdata

Based on experiences joint 2 was replaced.However joint 1 had much higher max PD magnitude than joint 2 !!!

After replacing joint 2 no problems occurred in the circuit.

Joint 1 type A: 24000pC

Joint 2 type B: 6000pC


CONCLUSIONS

• Combining PD measurements with withstand tests give much more information about the quality of the components

• After installation testing and diagnoses of new and old MV cable circuits by means of DAC gives reliable results

• Knowledge rules are developed for the determination of the condition of new and old cables and accessories


FURTHER STEPS

• Pilot project in 2011: implementation of DAC diagnoses on old 50kV XLPE cable circuits– 25 measurements– Development of knowledge rules– Condition evaluation and proposal for the future

• Consider to implement DAC technology for after installation test procedure on 50kV cable circuits


THANK YOU FOR YOUR ATTENTION

For more information:

[email protected]

jicable11, 19 - 23 june 2011 - versailles - france modern methods of installation and diagnostic...

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