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Lightning arrester connected between the line and earth in a power system
Protects the terminal equipment against traveling surges
Protects the terminal equipment against direct lightning stroke
Suppresses high-frequency oscillations in the line
Reflects back the traveling waves approaching it
Protects the terminal equipment against traveling surges
A lightning arrester (surge diverter) is a protective device connected in parallel with terminal equipment. It acts as a low-impedance path to the ground during high-voltage transients, diverting surge currents safely while maintaining normal operating voltage.
A lightning arrester (surge diverter) is a protective device connected in parallel with terminal equipment. It acts as a low-impedance path to the ground during high-voltage transients, diverting surge currents safely while maintaining normal operating voltage.
VresidualтАЛ<VBILтАЛ тАФ The residual voltage across the arrester must remain lower than the Basic Insulation Level of the protected equipment.
i(t)=ZsтАЛv(t)тИТVresтАЛтАЛ тАФ Calculation of surge current flow through the arrester during discharge.
When a traveling surge voltage exceeds the breakdown voltage of the arrester, the device triggers into a conducting state. The non-linear resistor (often made of Silicon Carbide or Zinc Oxide) provides a low-impedance path to earth. This limits the residual voltage across the equipment to a value below its Basic Insulation Level (BIL), preventing dielectric breakdown.
Lightning arresters are connected in parallel with the apparatus to be protected.
They operate by discharging the surge energy to the ground.
The device must have a non-linear VтИТI characteristic to revert to an open circuit at power-frequency voltages.
Zinc Oxide (ZnO) arresters are modern types that offer superior discharge capabilities without a series spark gap.
Protects expensive insulation from high-voltage stress.
Self-restoring after surge discharge.
Fast response time to steep-front waves.
Requires maintenance of ground connection integrity.
Potential for failure if the discharge capacity is exceeded by extreme surges.
Power transformers and switchgear.
Transmission line terminals.
Rotating machines and cable entries.
Option B is incorrect because a lightning rod (air terminal) handles direct strokes, whereas an arrester manages traveling surges resulting from strokes or switching.
Option C refers to shunt capacitors or damping circuits, not arresters.
Option D describes an open-circuited line, which causes wave doubling rather than suppression.
A is correct тАФ A lightning arrester acts as a voltage-sensitive switch that diverts dangerous traveling surges to the ground to protect sensitive electrical equipment insulation.
Always remember: lightning arresters are connected in parallel (shunt), while fuses are connected in series.