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In a power system lightning arresters are used to protect the electrical equipment against
Power frequency of over voltage
Direct stroke of lightning
Over current due to lightening stroke
Over voltage due to indirect lightening stroke
Over voltage due to indirect lightening stroke
Lightning arresters are protective devices connected in shunt to power equipment to limit surge voltages. They primarily shield equipment from over-voltages caused by traveling waves resulting from indirect lightning strokes (induced surges) or switching operations.
Lightning arresters are protective devices connected in shunt to power equipment to limit surge voltages. They primarily shield equipment from over-voltages caused by traveling waves resulting from indirect lightning strokes (induced surges) or switching operations.
VsurgeтАЛ=IтЛЕZsтАЛ тАФ represents the voltage surge magnitude related to surge current and line surge impedance.
R(V)=kтЛЕVтИТ╬▒ тАФ defines the non-linear resistance characteristic of the valve-type arrester.
The arrester acts as a non-linear resistor. Under normal operating conditions, it offers high resistance. When a surge voltage exceeding the breakdown value appears on the line, the arrester provides a low-impedance path to the ground, diverting the surge current and clamping the voltage to a safe level.
Lightning arresters are connected in parallel (shunt) with the equipment.
They must have a lower spark-over voltage than the insulation strength of the protected apparatus.
The surge impedance of the line determines the magnitude of the traveling wave voltage.
Modern arresters use Zinc-Oxide (ZnO) blocks for superior non-linear performance.
Effective limitation of transient over-voltages.
Capable of self-restoration after discharge.
Cannot protect against direct lightning strokes hitting the equipment itself.
Requires proper grounding to be effective.
Power transformers and reactors.
High voltage circuit breakers and switchgear.
Direct lightning strokes are typically handled by shield wires and lightning masts, not the arrester itself.
Option A refers to internal system phenomena like Ferranti effect or sudden load rejection, usually managed by tap changers or shunt reactors.
Indirect lightning strokes induce high electromagnetic fields on lines, causing traveling waves.
D is correct тАФ Lightning arresters are designed to discharge over-voltages resulting from indirect lightning strokes, preventing dielectric breakdown of insulation.
Always remember: Lightning arresters clamp voltage (shunt device), whereas reactors/capacitors manage steady-state power frequency voltage fluctuations.