An infinite bus-bar has

The correct answer is 'option 4'

Concept:

The bus whose voltage and frequency remain constant even after the variation in the load is known as the infinite bus.

The alternators operating in parallel in a power system are the example of the infinite bus. The on and off of any of the alternators will not affect the working of the power system.

• The capacity of a parallel operating system is enormous, their voltage and frequency remain constant even after the disturbance of the load.
• The connection and disconnection of any of the machines will not affect the magnitude and phase of voltage and frequency of an infinite bus.
•  In an infinite bus system, the voltage and frequency always remain constant.
• The synchronous impedance of the bus is low because of the parallel operations of the machine.