Join 60,000+ competitive exam aspirants
or with email
Your Cart
SubtotalтВ╣0
TotalтВ╣0
Examoogle тАв User тАв info@examoogle.com тАв EE-2024-8821
Chapter 1 of 12 тАв Page 1 of 248ЁЯФТ Protected PDF тАв Watermarked
Join 60,000+ competitive exam aspirants
A major part of short circuit takes place on exposed overhead lines, due to the insulator failure caused by the surge phenomenon
True
False
Can not say anything
True
Overhead transmission and distribution lines are highly susceptible to lightning strikes and switching surges, which generate high-voltage transients. These transients often exceed the Basic Insulation Level (BIL) of the insulators, leading to flashovers or permanent insulation failure, resulting in a line-to-ground short circuit.
Overhead transmission and distribution lines are highly susceptible to lightning strikes and switching surges, which generate high-voltage transients. These transients often exceed the Basic Insulation Level (BIL) of the insulators, leading to flashovers or permanent insulation failure, resulting in a line-to-ground short circuit.
VsurgeтАЛ>VwithstandтАЛ тАФ Condition for insulation flashover
ZcтАЛ=CLтАЛтАЛ тАФ Surge impedance of the transmission line
When a surge travels along an overhead line, it encounters the insulator strings. If the crest voltage of the surge exceeds the withstand voltage of the insulator string, the air gap ionizes, causing a breakdown. This ionization creates a low-resistance path for the system current to ground, manifesting as a short circuit or ground fault.
Overhead lines are the most vulnerable components in a power system due to their exposure.
Lightning is the most common cause of transient surges leading to insulator failure.
The protection of insulators is typically managed by using surge arresters and ground wires.
Flashovers can be either transient (self-restoring) or permanent (damage to insulator discs).
Understanding this helps in selecting appropriate Insulation Coordination levels.
Allows for the optimized placement of lightning arresters.
High cost of maintaining high-voltage insulation under extreme environmental conditions.
Flashovers lead to frequent transient outages in power systems.
Design of overhead transmission lines.
Insulation coordination studies for HV and EHV substations.
Basic Insulation Level (BIL) is the critical reference point for equipment insulation withstand capacity.
Option B (False) is incorrect because empirical data in power system reliability shows that lightning-induced insulator failures are the leading cause of short circuits in overhead networks.
A is correct тАФ Surge phenomena significantly elevate the voltage across insulator strings beyond their dielectric strength, resulting in flashovers that manifest as short circuits.
Always remember that while switching surges are significant, lightning strikes are the primary cause of insulation failure on lines rated below 400kV.