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Examoogle • User • info@examoogle.com • EE-2024-8821
Chapter 1 of 12 • Page 1 of 248🔒 Protected PDF • Watermarked
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A shunt fault is characterized by
Increase in current, frequency and power factor
Increase in current reduction in frequency and power factor
Increase in current and frequency but reduction in power factor
None of the above
Increase in current reduction in frequency and power factor
A shunt fault occurs when a low-impedance path is established between a phase and ground or between two phases, causing a significant increase in fault current. This abrupt surge in load current causes the generator speed (and thus system frequency) to drop and the power factor to decrease due to the inductive nature of the fault current.
A shunt fault occurs when a low-impedance path is established between a phase and ground or between two phases, causing a significant increase in fault current. This abrupt surge in load current causes the generator speed (and thus system frequency) to drop and the power factor to decrease due to the inductive nature of the fault current.
If=Zth+ZfVth — Fault current magnitude calculation
Pacc=Pm−Pe=ωs2Hdt2d2δ — Swing equation representing rotor deceleration during fault
The sudden connection of a low-impedance path (shunt) leads to a dramatic drop in the local voltage magnitude. According to the power swing equation, the increase in electrical load demand (fault power) without a corresponding change in mechanical input power from the prime mover leads to a deceleration of the rotating mass, reducing system frequency. The fault current is largely reactive, pushing the overall system power factor toward a lagging state.
Shunt faults result in high magnitude fault currents, often exceeding rated values by several multiples.
System frequency drop is a result of the electromagnetic braking effect caused by the increased electrical load on the generators.
Low power factor is characteristic of shunt faults because the fault path is predominantly inductive.
Frequency decay rate depends on the inertia constant (H) of the system generators.
High current makes detection via overcurrent relays efficient
Predictable fault behavior aids in protection coordination
Causes severe thermal stress on conductors and equipment
May lead to voltage collapse if not cleared promptly
Setting relay trip thresholds
Power system stability analysis
Shunt faults include Single Line-to-Ground (SLG), Line-to-Line (LL), and Double Line-to-Ground (DLG) faults.
Option A is incorrect because frequency and power factor always decrease under shunt faults, they do not increase.
B is correct — Shunt faults create an abnormal current surge, causing an inductive load increase that decelerates generators and forces power factor to decline.
Always remember that in power systems, an increase in electrical load demand without a simultaneous increase in mechanical input power leads to frequency reduction.