BEST PRACTICES FOR OFFLINE DIAGNOSIS OF MV CABLES 6.4 H Putter.pdf · Source: IEEE 400.2 (2013) –...
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1 BEST PRACTICES FOR OFFLINE DIAGNOSIS OF MV CABLES HEIN PUTTER Productmanager cable testing and -diagnosis Megger Site Germany 13 th Insucon conference – 16 -18 th Mai 2017, Birmingham, UK
Transcript of BEST PRACTICES FOR OFFLINE DIAGNOSIS OF MV CABLES 6.4 H Putter.pdf · Source: IEEE 400.2 (2013) –...
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BEST PRACTICES FOR OFFLINE DIAGNOSIS OF MV CABLES
HEIN PUTTERProductmanager cable testing and -diagnosis
Megger Site Germany
13th Insucon conference – 16 -18th Mai 2017, Birmingham, UK
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Agenda■ Introduction■ Case Study: Acceptance/ commissioning testing■ Case Study: Condition Monitoring■ Summary & Conclusions
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Introduction Offline cable diagnostics on MV cables are nowadays widely accepted
and in some countries already standardized (for commissioning)
This, as it is known that a pure withstand test will not identify all workmanship issues
In addition, offline cable diagnostics are also very useful for condition assessment of service aged MV cables
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Introduction Offline cable diagnostics we need to divide into:
• PD diagnostics • Dielectric diagnostics
Dielectric diagnostics are mainly performed on service aged cables only, most familiar method is a dielectric loss measurement (tanDelta)
Offline PD diagnostics can be performed with a number of excitations voltages each having their own benefits
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Introductioncontinuous AC
sinusoidal
0.1 Hz
Damped AC Cosine rectangular
50 Hz
20 - 300 Hz
20 - 500 Hz 0.1 Hz 20 - 300 Hz
Ground wave
Transition
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Agenda■ Introduction■ Case Study: Acceptance/ commissioning testing■ Case Study: Condition Monitoring■ Summary & Conclusions
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Case Study: Acceptance testing
Commissioning test on a newly installed XLPE cable
Operation voltage: 12/20 kV Cable length: 2308 m Cable type: XLPE, 3x1x240 mm2
Joints: 7 Year of installation: 2016 Withstand test: passed (3Uo, 60 minutes)
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Case Study: Acceptance testing TanDelta Measurement
Source: IEEE 400.2 (2013) – Table G.1
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Case Study: Acceptance testingPD Mapping @ Uo PD Mapping @ 2Uo
DAC Excitation Voltage
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Case Study: Acceptance testingPD Mapping @ Uo PD Mapping @ 2Uo
Sinus Excitation Voltage (measurement from far end)
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Case Study: Acceptance testingSummary: Withstand test at 3Uo for 60 minutes did not identify weak spot.
tanDelta measurement showed „further study advised“, althoughcable is new typical behaviour for new co-polymer cables/ resistive field stress control heat shrink joints
tanDelta measurement did not identify local problem in phase L3
Both excitation voltages (VLF sinus 0.1 Hz and DAC) showedcomparable results (PDIV, PD intensity and PD level)
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Agenda■ Introduction■ Case Study: Acceptance/ commissioning testing■ Case Study: Condition Monitoring■ Summary & Conclusions
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Case Study: Condition MonitoringCondition monitoring on a service aged mixed cable
Operation voltage: 12/20 kV Cable length: 653 m Cable type : Mixed cable (XLPE, paper insulated) Joints: 7 Year of installation: 1973
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Case Study: Condition Monitoring TanDelta Measurement
tanDelta results Local problem in L3
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Case Study: Condition Monitoring Fault located in L3 positioned at 470m, not caused by
external damage, pure internal fault.
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Case Study: Condition MonitoringPD Mapping @ Uo PD Mapping @ UoVLF Sinus 0.1Hz VLF CR 0.1Hz (210Hz)
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Case Study: Condition MonitoringPD Mapping @ 2Uo PD Mapping @ 2UoVLF Sinus 0.1Hz VLF CR 0.1Hz (210Hz)
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Case Study: Condition MonitoringSummary: tanDelta measurement helped to identify local problem
PD diagnosis with VLF Sinus 0.1Hz did not identify the fault position, VLF CR did
At operating voltage cable, apart from failure position, PD free
At elevated voltages several PD defects in accessories localised
Trending measurement recommended after 3 years
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Agenda■ Introduction■ Case Study: Acceptance/ commissioning testing■ Case Study: Condition Monitoring■ Summary & Conclusions
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Summary & ConclusionsCommissioning testing: Withstand testing only is not sufficient as a commissioning test
tanDelta diagnosis on a new cable can be misleading (co-polymer/ local problem)
PD diagnostics are strongly recommended
Excitation voltage should be comparable to operatingfrequency
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Summary & ConclusionsCondition monitoring: For condition monitoring in addition a tanDelta diagnosis is
recommended
A tanDelta diagnosis can also identify local problems
Excitation voltage should be comparable to operatingfrequency, differences between Sinus 0.1Hz and DAC or VLF CR have been observed.
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Questions ?
