Join 60,000+ competitive exam aspirants
or with email
Your Cart
Subtotal₹0
Total₹0
Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
Join 60,000+ competitive exam aspirants
The source of heat generation in cables is
Copper loss in conductor
Dielectric loss in cable insulation
Losses in metallic sheath and armouring
All of above
All of above
Heat generation in underground cables is a cumulative effect caused by energy dissipation through electrical and dielectric losses. All three processes—resistive heating in the conductor, dielectric hysteresis in the insulation, and eddy currents in the metal sheath—contribute to the total thermal load of the cable system.
Heat generation in underground cables is a cumulative effect caused by energy dissipation through electrical and dielectric losses. All three processes—resistive heating in the conductor, dielectric hysteresis in the insulation, and eddy currents in the metal sheath—contribute to the total thermal load of the cable system.
Pcu=I2Rc — Copper loss in the conductor
Pd=ωCV2tanδ — Dielectric loss in insulation
The total heat generated (Wtotal) is the sum of I2R copper losses in the conductor, dielectric losses (Wd) due to molecular polarization in the insulation material under high voltage, and circulating currents or eddy current losses induced in the metallic sheath and armouring. These losses convert electrical energy into thermal energy, raising the cable temperature until thermal equilibrium with the surrounding soil is reached.
Copper losses are load-dependent (I2R loss).
Dielectric loss is significant in high-voltage cables due to the capacitive nature of insulation.
Metallic sheath losses include eddy current and sheath circulating current losses.
Total heat generated determines the current carrying capacity (ampacity) of the cable.
Comprehensive understanding of thermal rating
Essential for designing underground transmission cooling systems
High heat levels reduce the life expectancy of insulation materials (Arrhenius law)
Increases ohmic resistance, further worsening efficiency
Power system planning
Cable derating calculations
Thermal design of HV underground lines
The dielectric loss depends on the operating voltage and the dissipation factor (tanδ) of the insulation material.
Option A is limited only to conductor heating; Option B focuses only on insulation losses; Option C ignores the primary copper losses.
D is correct — The total heat generated in a cable is the summation of copper losses, dielectric losses, and losses occurring in metallic components like sheaths and armouring.
Always remember that while copper loss is independent of voltage (but dependent on current), dielectric loss is proportional to the square of the voltage (V2), making it critical for EHV/UHV cable design.