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Effect on wavefront steepness by surge absorber is
Decrement
Increment
Zero
None of above
Decrement
Quick Summary: A surge absorber is a protective device used in power systems to reduce the steepness of the wavefront of incoming lightning or switching surges. By decreasing the steepness (rate of rise of voltage $dv/dt$), it protects the sensitive insulation of transformer windings from high-voltage stress.
A surge absorber is a protective device used in power systems to reduce the steepness of the wavefront of incoming lightning or switching surges. By decreasing the steepness (rate of rise of voltage dv/dt), it protects the sensitive insulation of transformer windings from high-voltage stress.
S=dtdv — Steepness represents the rate of voltage rise per unit time
i=Cdtdv — Current through the capacitor is proportional to the surge steepness
The surge absorber typically consists of a capacitor and a resistor connected in series between the phase and ground. The capacitor acts as a low impedance path for high-frequency transients, effectively flattening the surge, while the series resistor absorbs the energy of the surge. This mechanism significantly slows down the wavefront rise time, thereby limiting the internal voltage gradients within electrical equipment.
Surge absorbers protect against steep-fronted voltage surges.
They are connected in parallel with the apparatus to be protected (e.g., transformer).
Unlike surge arresters, which primarily limit the peak magnitude, surge absorbers focus on reducing dv/dt.
Commonly used in conjunction with lightning arresters for comprehensive protection.
Reduces the severity of stress on transformer turn-to-turn insulation
Prevents oscillations in the winding
Improves reliability of high-voltage transformers
Adds cost and physical size to the substation installation
Requires periodic maintenance of the capacitor units
Transformer winding protection
High-voltage rotating machine terminal protection
The capacitor-resistor combination is often referred to as an R-C surge absorber.
Option B (Increment) is incorrect because an increase in steepness would increase the dielectric stress, damaging the insulation.
A is correct — A surge absorber reduces the wavefront steepness by increasing the wavefront rise time, thereby minimizing voltage gradients.
In competitive exams, always distinguish between Surge Arresters (limit peak magnitude) and Surge Absorbers (limit the rate of rise or steepness dv/dt).