Condition assessment on Submarine power cable 6,3-72,5 kV
There are thousands of submarine cables around the world and most of them are a important part of the infrastructure. A great deal of these cables is also well above life expectancy. However, the age itself does not mean that the cables are in bad condition.
However, a Hipot insulation test with PD & TD diagnosis will reveal the the actual health condition
Damped AC with PD/TD diagnose ( 20-300 Hz)
The DAC technology makes it possible to test long cables with high capacitance, without a high power requirement. The test frequency depends on the capacitance of the test object and will be between 20 and 300 Hz. With one-sided measurement, a minimum of 10 km of cable can be tested. For extra-long cables, two-sided measurement can be used.
With a low noise level and a test frequency between 20-300 Hz, the test object is exposed to conditions similar to normal operation (50 Hz). This ensures that the results of PD diagnosis and TD diagnosis are credible.
DAC testing is in compliance with the following standards and recommendations:
DAC PD diagnose:
Partial discharges (PD) are the main contributor to the insulation breakdown in cable systems. With DAC PD diagnosis, small weaknesses in cables, joints and terminations, that otherwise would pass a pressure-test, will be revealed.
- PD measurement according to; IEC 60270, IEC 60885-3, IEEE 400.3
- All types of cables from 6.3 to 72.5 kV
- With a one-sided measurement, a minimum of 10 km of cable can be tested. For extra long cables, double-sided measurement can be used
- PD mapping (Localization <1 meter)
- PDIV (Inception voltage)
- PDEV (Extinction voltage)
- PRPD (PD pattern)
- PD level (Amplitude / Repetition Rate)
- PD pattern and results comparable to normal 50 Hz
Reveals typical installation defects in joints and terminations such as:
Poorly prepared pex surface (knife cuts and impurities)
Poor semiconductor removal
Poor shrinkage
Misalignment of the stress control
DAC TD diagnosis:
DAC Tandelta detects dielectric losses that occur in insulation weaknesses. DAC TD is especially useful for detecting aging and degrading the insulation in paper cables.
- Dipole losses (General aging)
- Interface losses
- PD discharges (Partial discharges
LIRA (Line Resonance Analysis)
An LIRA test detects all types of changes that affect cable capacitance. LIRA is perfect for detecting dimensional changes such as joints or areas affected by extensive heating, water ingress, corrosion, bending, scratching, mechanical damage, fatigue and global or local degradation of the insulation material.
LIRA can also be used to locate the fault location once the accident has occurred.
Benefits of LIRA test:
- Non-destructive test
- Can be used on cables up to 300 km
- Reveals all changes affecting cable capacitance
- Follow developments over time
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