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Oil filled cables has the drawback of
No possibility of impregnation after sheathing
Greater cost and complicated installation of cables and maintenance
High thermal resistance
All of above
Greater cost and complicated installation of cables and maintenance
Oil-filled cables are designed to eliminate voids within the insulation using pressurized oil. While this significantly improves dielectric strength and prevents ionization, the requirement for auxiliary equipment like oil reservoirs, pressure gauges, and pumps increases the system cost and makes installation and maintenance substantially more complex compared to solid cables.
Oil-filled cables are designed to eliminate voids within the insulation using pressurized oil. While this significantly improves dielectric strength and prevents ionization, the requirement for auxiliary equipment like oil reservoirs, pressure gauges, and pumps increases the system cost and makes installation and maintenance substantially more complex compared to solid cables.
EmaxтАЛ=rln(R/r)VтАЛ тАФ Maximum electric stress in a cable, which oil-filled systems manage better by removing air voids.
P=dtdVтАЛ тАФ Maintenance pressure requirements for dielectric integrity.
The cable contains channels through which thin insulating oil flows under positive pressure. This pressure ensures that any potential voids or gas bubblesтАФwhich are primary sites for partial discharge and electrical breakdownтАФare filled or compressed. This mechanism allows oil-filled cables to operate at higher electric stress gradients (e.g., up to 230 kV and above) while maintaining long service life.
Used for extra high voltage (EHV) levels, typically 66 kV and above.
Positive pressure prevents air entry and subsequent corona discharge.
Higher complexity due to oil tanks and expansion vessels.
Capable of carrying larger current loads without excessive insulation degradation.
Higher dielectric strength
Self-healing properties regarding small insulation gaps
Suitable for very high voltage applications
High initial and maintenance costs
Risk of oil leakage leading to environmental impact
Requirement for auxiliary pressure maintenance equipment
Submarine power transmission
High-voltage underground urban distribution
Inter-connector links in national grids
Oil-filled cables are generally used when solid-type cables reach their limitation in voltage rating (typically above 33 kV).
Option A is incorrect because oil-filled cables are specifically designed to allow for oil impregnation processes. Option C is incorrect as oil-filled cables generally have better thermal conductivity than solid insulation with gas-filled voids.
B is correct тАФ Oil-filled cables require auxiliary pressure-maintaining equipment which significantly raises the capital cost and complicates site installation and routine maintenance.
Always remember that as cable voltage ratings increase, the necessity for void-free insulation becomes paramount, leading to the transition from solid insulation to pressurized oil or gas-filled systems.