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Which is an external cause of voltage surge
Lightning
Switching surge
Arcing ground
Resonance
Lightning
Voltage surges are transient overvoltages that occur on power systems, categorized as either internal or external based on their origin. Lightning is an external cause because it involves atmospheric electrical discharges that inject large currents into the power line, causing massive potential rises independent of the system's own operational state.
Voltage surges are transient overvoltages that occur on power systems, categorized as either internal or external based on their origin. Lightning is an external cause because it involves atmospheric electrical discharges that inject large currents into the power line, causing massive potential rises independent of the system's own operational state.
VsurgeтАЛ=IstrikeтАЛ├ЧZsurgeтАЛ тАФ The voltage developed by an incoming lightning surge
ZsurgeтАЛ=CLтАЛтАЛ тАФ Surge impedance of a transmission line
Lightning strikes (either direct or indirect) inject massive amounts of charge into the overhead lines. This results in a traveling wave of high voltage, defined by V=I├ЧZsтАЛ, where I is the surge current and ZsтАЛ is the surge impedance of the line. The potential exceeds the insulation strength of the equipment, necessitating surge arresters for protection.
External surges are caused by atmospheric phenomena like lightning or electrostatic induction.
Internal surges are caused by system operations like switching or faults.
Lightning causes surges by direct contact or induction due to electromagnetic fields from a nearby strike.
Surge arresters (like ZnO arresters) are used to divert these surge currents to the ground.
Lightning rods and overhead shield wires provide high protection against direct strikes.
Surge arresters clamp the voltage at a safe level for equipment.
Extreme high frequency and steep wavefronts can damage transformer inter-turn insulation.
High energy dissipation requirements for arresters during severe storms.
Insulation coordination in high-voltage substations.
Protection of power transformers and circuit breakers.
Switching surges (Option B) are internal surges caused by the rapid change of energy stored in magnetic and electric fields during circuit breaking.
Arcing ground (Option C) is an internal cause related to transient oscillation in systems with insulated or resonant grounded neutrals.
Resonance (Option D) is an internal phenomenon where inductive and capacitive reactances cancel, causing high-voltage magnification.
A is correct тАФ Lightning is an external cause of voltage surge because it originates from atmospheric discharges outside the electrical power system.
Always remember: Anything caused by weather/atmospheric conditions is 'External', while anything caused by the system's own operation/faults is 'Internal'.