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Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
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Oil filled cables has the advantage of
No ionization, oxidation and formation of voids
Possibility of increased temperature range in service
More maximum permissible stresses
All of above
All of above
Oil-filled cables utilize low-viscosity oil under pressure within the cable insulation to prevent the formation of voids and eliminate ionization, which are primary causes of dielectric breakdown. This system maintains cable integrity at higher operating temperatures and electrical stresses compared to standard solid-type insulated cables.
Oil-filled cables utilize low-viscosity oil under pressure within the cable insulation to prevent the formation of voids and eliminate ionization, which are primary causes of dielectric breakdown. This system maintains cable integrity at higher operating temperatures and electrical stresses compared to standard solid-type insulated cables.
EmaxтАЛ=rln(R/r)VтАЛ тАФ Maximum electric stress at the conductor surface
╧Г=AQтАЛ тАФ Relation between stress and charge distribution in the dielectric
In oil-filled cables, a reservoir is connected to the cable to maintain a positive pressure of insulating oil. This pressure ensures that any gas bubbles or voids formed due to thermal expansion or contraction are filled with liquid oil, which has a higher dielectric strength than gaseous pockets. Consequently, it suppresses partial discharges and allows the cable to withstand higher electric field gradients (stresses) safely.
Oil-filled cables are specifically designed for high-voltage applications (typically 66kV and above).
Pressure maintenance avoids the 'ionization of voids' phenomenon which causes treeing and failure.
Higher viscosity stability allows for better heat dissipation compared to solid mass-impregnated insulation.
Elimination of internal voids preventing partial discharge
Higher permissible dielectric stress
Capability to operate at higher thermal loads
Self-healing properties of the liquid dielectric
Complex maintenance due to oil reservoir systems
Higher installation and capital costs
Risk of oil leakage/contamination
Extra high voltage (EHV) underground power transmission
Submarine power cables
Long-distance urban high-voltage distribution
The oil used is typically a highly refined mineral oil with excellent dielectric properties.
Options A, B, and C are all valid technical advantages of oil-filled systems, making 'All of the above' the only complete answer.
D is correct тАФ Oil-filled cables provide superior dielectric stability by eliminating voids, supporting higher stresses, and allowing increased temperature operation.
Always remember that in EHV cables, ionization starts at voids where the local electric stress exceeds the dielectric strength of the gas; oil-filled cables fundamentally prevent this by replacing gas with liquid.