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Examoogle • User • info@examoogle.com • EE-2024-8821
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Pressure cables are generally not used beyond
11 kV
33 kV
66 kV
132 kV
66 kV
Quick Summary: Pressure cables are specialized cables that use oil or gas under high pressure to prevent ionization in the dielectric insulation. These cables are designed for Extra High Voltage (EHV) applications, typically starting from 66 kV and extending up to 275 kV or higher, to mitigate the risk of voids causing dielectric breakdown.
Pressure cables are specialized cables that use oil or gas under high pressure to prevent ionization in the dielectric insulation. These cables are designed for Extra High Voltage (EHV) applications, typically starting from 66 kV and extending up to 275 kV or higher, to mitigate the risk of voids causing dielectric breakdown.
Ed=rln(R/r)V — Electric stress calculation in a cable where R is sheath radius and r is conductor radius.
The principle relies on maintaining the dielectric material under high pressure. Voids or air bubbles, which are areas of low electrical strength prone to ionization, are collapsed or filled by the pressurized medium (oil or nitrogen gas). This significantly increases the dielectric strength and prevents the formation of corona discharges within the cable insulation.
Pressure cables utilize oil-filled or gas-filled mechanisms to suppress ionization.
Ionization in insulation is a primary cause of insulation failure in high-voltage cables.
Used extensively in underground transmission lines where overhead lines are impractical.
They are economically viable only for high-voltage levels (typically >66 kV).
Higher current carrying capacity compared to solid cables.
Excellent dielectric strength due to suppression of voids.
Suitable for very high voltage transmission.
Complex maintenance and installation requirements.
High initial capital cost.
Potential for oil leakage in oil-filled types.
Submarine power cables.
High-voltage underground transmission systems in metropolitan areas.
Below 66 kV, solid cables or belted cables are typically preferred due to their cost-effectiveness and simpler construction.
Option D (132 kV) is a standard operating voltage for pressure cables, confirming it is well within their functional range.
C is correct — Pressure cables are generally used for high voltage applications above 66 kV; they are not typically used at or below 66 kV due to the cost and complexity involved.
Always remember that cable selection is a trade-off between insulation cost, thermal limit, and operating voltage; pressure cables are the premium choice for EHV requirements.