Condition assessment on MV & HV cables
Condition assessment provides knowledge about the state of the various components in HV grids. This knowledge contributes to the right decisions regarding maintenance and replacement. Condition based-maintenance improves the overall performance at a lower cost
Test av høyspentkabel
lokalisering av isolasjonsfeil i høyspentkabel
Test av høyspentkabel
Cable diagnosis with Damped AC (DAC)
Damped AC is a proven and recognized technology for high voltage diagnostic testing with application of IEEE, IEC, CENELEC and Cigrè.
With a test frequency between 20-500 Hz similar conditions as during normal operation (50Hz) are achieved. This helps to detect weaknesses that are active during normal operation. The diagnosis can be performed on all types of cables from 6.3 to 72,5 kV. With single-sided measurement, a minimum of 10 km of cable tested. For extra-long cables, two-sided measurement can be used.
DAC PD diagnosis:
PD testing is the best way to reveal and locate weaknesses in cable, joints and terminations. PD diagnosis with DAC reveals small weaknesses in cables, joints and terminations that otherwise whould pass an pressure test.
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PD measurements according to; IEC 60270, IEC 60885-3, IEEE 400.3
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PD mapping (Localization < 1 meter)
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PDIV (inception voltage)
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PDEV (extinction voltage)
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PRPD
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PD level (Amplitude/Repetitionrate)
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PD patterns and parameters similarity between the results of DAC tests and continuouspower frequency (50/60 Hz) factory tests
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Reveals typically installation errors in joints and terminations such as;
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Bad XLPE insulation preparation (cuts & dirt)
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Poor removal of the semicon
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Poor heat shrinking technique
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Wrong stress control assembly
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Damped AC methodology is in accordance with relevant international standards and recommendations:
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IEC 60060-3
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IEC 60502
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IEC 60270
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IEC 60885-3
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IEC 60141
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IEEE 400
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IEEE 400.4
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IEEE 400.3
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CIGRÈ Technical Brochure 502
DAC TanDelta diagnosis:
TanDelta diagnosis with DAC reveals aging due to different losses in high voltage cables. DAC TD is particularly useful for detect aging and degradation of insulation in oil/paper cables
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Dipole losses (General aging)
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Interface losses (Interface problems)
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PD losses (Partial discharge)
Partial discharge (PD) is regarded as the best early warning indicator of insulation degredation in MV & HV assets.
The PD survey reveals and locates faults without service interruption. This is a complex PD survey which captures the PD pattern with it`s waveform and the frequency spectrum of every PD pulse that the fault generates. This provides the complete information regarding the activity so that appropriate measures can be taken
The survey is suitable for any electrical equipment from 3kV to 600kV. The meausurments will also pick up PD signals from faluts at a distance. This means that we can detect faults in cable/joints far from the measurement point. How far depends on the attenuation and propagation in the cable.
Source: IEEE 493-1997 (GOLD BOOK)
A PD survey will:
• Reveal insulation weaknesses in MV & HV systems
• Increase reliability in MV & HV assets
• Increase asset longevity
• Increase safety
• Reduce Risk
• Reduce maintenance costs moving from preventive to condition based-maintenance
Kontroll av kabelanlegg. Test av høyspentkabel
Kontroll av høyspentanlegg uten driftsstans
ONLINE PD
Kontroll av kabelanlegg. Test av høyspentkabel
Online PD Survey
The TanDelta measurement (dissipation factor) is a non-destructive and integral procedure that serves to evaluate the condition of an entire cable route. With the dielectric dissipation factor tan δ, the relation of effective power to reactive power of the cable is measured.
Benefits of VLF TD Diagnostic Testing
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TanDelta at 0,1 Hz is the best way to expose water-treeingin XLPE insulation
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VLF Tandelta (TD) uncovers the general aging of the insulation and creates a fingerprint of the insulation system
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Test voltage at or below operating voltage U0 of the cable ensures a non-destructive condition assessment on aged cable and still gives good information about the condition of the cable
Vanntrevekst i høyspentkabel
Høyspent testing med fingeravtrykk for senere kontroll av kabel
TanDelta måling høyspentkabel
Vanntrevekst i høyspentkabel
VLF tan δ Diagnosis
Source: IEEE 400.2-2013
Source: IEEE 400.2-2013
Høyspent kabeldiagnose avslører kabelfeil før havari
Kabeldiagnose
Avdekker og lokaliserer dårlige høyspentskjøter
Høyspent kabeldiagnose avslører kabelfeil før havari
VLF PD Diagnosis
Hipot PD testing may reveal and locate weaknesses in cable, joints and terminations. With a high voltage source the cable is exposed to an overvoltage up to 1,7*operating voltage. At the same time any PD activity will be measured. PD at operation voltage is critical and should be adressed immediately. If the PD only is triggerd by an overvoltage it still is critical but not that urgent.
This will reveal:
▪ Localisation of the PD fault within few meters
▪ The types of fault with PRPD
▪ PD level
▪ PD inception voltage / extinction voltage
▪ PD in cable termination, joints and cables
PD activity can be caused by:
Poor workmanship, manufacturing defects, transport damage and excavation damage can generate insulation weaknesses which in turn cause partial discharges under electrical stress. This will over time cause a breakdown!
Kontroll av høyspentkabel
Kabeldiagnose
Isolasjonstest høyspentkabel
Kontroll av høyspentkabel
VLF Withstand test
The purpose of a withstand test is to verify the integrity of the cable under test. If the test cable has a defect severe enough at the withstand test voltage, an electrical tree will initiate and grow in the insulation. Inception of an electrical tree growth are functions of several factors including test voltage, source frequency and amplitude, and the geometry of the defect.
Maintenance test according to;IEEE 400.2-2013
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Good insulation will be unaffected
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Reveals; Production deviations, poor workmanship and aging.
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Uses sinusoidal, 0.1Hz waveform
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30 min test time
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Up to 30 km cable can be tested
Insulation testing of AC Electric Machinery with High voltage at Very Low Frequency IEEE Std 433-2009
LIRA is sensitive to small changes of wire electric parameters, mainly the insulation permittivity, that are a significant condition indicator of the cable state (thermal and radiation aging, humidity, insulation defects, mechanical damage).
LIRA can detect:
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All types of changes affecting the insulation capacitance
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Dimensional changes as cable joints or splices between different cable types, areas influenced by extensive heating, radiation, water intrusion, corrosion, bends, scratches, mechanical impacts, fatigue, etc.
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Global or local insulation material degradation (XLPE, PILC and others).
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All types of changes affecting the insulation capacitance
LIRA might detect:
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Damages in outer sheath only if water/
humidity or other factors directly or indirectly
affects the capacitance of the insulation/screen
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High resistance failure depending on extent ofchange and size
Avdekker feilstedet i høyspentkabel
Test av høyspentkabel
Avdekker feilstedet i høyspentkabel
LIne Resonance Analysis
Kappetest
Kappetest
Cable sheath resistance
Healthy sheath insulation is very important for the safe operation of power cables. If the sheath is damaged the cable's life will be obviously shortened.
Neka has the equipment and expertise to perform mantle test on long cables, both as commissoing on new installations and condition assesment on old cables.