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The force which are most likely to occur in underground cables are
Breakdown of cable insulation
Short circuit faults
Open circuit faults
All of above
All of above
Underground cables are complex multi-layered structures consisting of conductors, insulation, metallic sheaths, and protective bedding/armor. Failures occur due to thermal, electrical, and mechanical stresses that compromise the integrity of these layers, leading to operational faults.
Underground cables are complex multi-layered structures consisting of conductors, insulation, metallic sheaths, and protective bedding/armor. Failures occur due to thermal, electrical, and mechanical stresses that compromise the integrity of these layers, leading to operational faults.
RinsтАЛ=2╧АL╧БтАЛln(dDтАЛ) тАФ Insulation resistance formula showing dependence on material properties and dimensions
C=ln(D/d)2╧А╧╡0тАЛ╧╡rтАЛтАЛ тАФ Capacitance per unit length governing dielectric stress
The primary causes of failure include insulation degradation due to thermal cycling (aging), moisture ingress through sheath damage, mechanical stress from soil movement or improper installation, and electrical stress from overvoltages. These result in dielectric breakdown (insulation failure), low-impedance paths between conductors or ground (short circuits), or complete severing of the conductor (open circuit).
Underground cables are more expensive to repair compared to overhead lines because the fault location is buried.
Thermal stress accelerates insulation aging according to the Arrhenius equation.
The metallic sheath is crucial for moisture protection and controlling electric stress.
Common techniques for fault localization include Murray Loop test, Varley Loop test, and Pulse Echo (TDR) testing.
Immune to lightning and wind damage
Enhanced safety in densely populated areas
Minimal maintenance compared to overhead lines
High initial cost
Difficult and slow fault detection/location
Susceptible to thermal insulation degradation over time
Power transmission in urban/congested areas
Submarine cable power distribution
Internal building wiring and industrial plant electrification
Insulation breakdown often results from 'treeing'тАФa degradation process where partial discharges slowly erode the insulation material.
Short circuits are typically caused by mechanical damage from digging (excavation) or insulation failure under surge conditions.
Open circuit faults are rarer and usually occur due to excessive mechanical strain on the conductor during installation or soil shifting.
D is correct тАФ Underground cable systems are subject to various electrical and physical failure modes including insulation degradation, short circuits, and open circuits.
Always remember that while underground cables have high reliability, they are prone to hidden damage; therefore, 'all of the above' is the standard answer for common failure types in such systems.