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An infinite bus in power system is
A small system whose voltage varies with the power exchange between the synchronous machine and bus
A large system whose voltage and frequency varies with the power exchange between synchronous machine and bus
A large system whose voltage and frequency remains constant independent of power exchange between synchronous machine and bus
A large system with infinite voltage
A large system whose voltage and frequency remains constant independent of power exchange between synchronous machine and bus
Quick Summary: An infinite bus is a theoretical model of an idealized power system so large that its terminal voltage and frequency remain constant regardless of the amount of real or reactive power injected into or withdrawn from it. It acts as an ideal voltage source with zero internal impedance.
An infinite bus is a theoretical model of an idealized power system so large that its terminal voltage and frequency remain constant regardless of the amount of real or reactive power injected into or withdrawn from it. It acts as an ideal voltage source with zero internal impedance.
Vbus=V∠0° — constant voltage phasor
f=fnominal — constant system frequency
Because the capacity of the infinite bus is effectively infinite, the voltage vector V and frequency f are unaffected by the operational fluctuations of any individual connected synchronous machine. This allows the connected generator to be modeled as an voltage source behind an impedance Zs connected to a fixed bus, simplifying stability analysis.
An infinite bus has zero internal impedance (Thevenin equivalent impedance = 0).
It maintains a constant voltage magnitude and frequency despite changes in load or generation.
It is a useful reference point for analyzing the power angle stability of synchronous generators.
The power flow equation simplifies to P=XsEVsin(δ) when connected to an infinite bus.
Simplifies power system stability studies significantly.
Provides a stable reference for synchronization of new generators.
Purely a mathematical idealization; physical systems always have some impedance and voltage droop.
Does not account for real-world transmission line losses or local disturbances.
Synchronous machine stability analysis.
Load flow studies and grid integration modeling.
Option A describes a weak grid or local bus, not an infinite bus.
Option B describes a realistic power grid, but not the idealized infinite bus concept.
In practice, a very large utility grid is approximated as an infinite bus for transient stability simulations.
C is correct — An infinite bus is defined by its ability to maintain constant voltage and frequency irrespective of power exchanges.
Remember that the infinite bus acts as a 'slack bus' in power flow studies, where the voltage magnitude and angle are fixed, and the slack bus provides the balancing power.