In a three-phase balanced star-connected load, connected to a three-phase, three-wire balanced supply of 400 V, potential of the neutral point of load is: (with respect to ground)

Explanation:

Three-Phase Balanced Star-Connected Load

Definition: In a three-phase balanced star-connected load, each phase carries the same current, and the phase voltages are equal in magnitude but are phase-shifted by 120 degrees from each other. The star connection means that one end of each of the three loads is connected to a common point called the neutral point.

Working Principle: In a star connection, the line voltage (the voltage between any two lines) is √3 times the phase voltage (the voltage between any line and the neutral point). For a balanced load, the currents in each phase are equal in magnitude and phase angle, and the vector sum of the currents at the neutral point is zero. This means that the neutral point is at the same potential as the ground in a balanced system.

Advantages:

• Provides a stable neutral point.
• Allows for the use of a lower voltage between any phase and neutral, which can be safer for certain applications.
• Facilitates the distribution of both single-phase and three-phase power.

Disadvantages:

• Requires more conductors compared to a delta connection for the same power level.
• In case of an unbalanced load, the neutral point can shift, causing voltage imbalances.

Applications: Three-phase star-connected systems are widely used in power transmission and distribution, as well as in various industrial applications where balanced loads are common, such as in motors and other heavy machinery.

Correct Option Analysis:

The correct option is:

Option 1: 0 V

This option correctly describes the potential of the neutral point of the load with respect to the ground in a balanced three-phase star-connected system. Since the system is balanced, the vector sum of the currents at the neutral point is zero, making the neutral point at the same potential as the ground.

Additional Information

To further understand the analysis, let’s evaluate the other options:

Option 2: 400 V

This option is incorrect because 400 V is the line voltage in the three-phase system, not the potential of the neutral point. The line voltage is the voltage between any two lines, and in a balanced system, the neutral point is at 0 V with respect to the ground.

Option 3: 230 V

This option is incorrect as well. 230 V is approximately the phase voltage of the system (400 V / √3), but it is not the potential of the neutral point. The neutral point in a balanced system remains at 0 V with respect to the ground.

Option 4: 680 V

This option is incorrect because 680 V is not a standard voltage value in a three-phase system and does not relate to the potential of the neutral point. The neutral point potential is 0 V in a balanced star-connected system.

Conclusion:

Understanding the behavior of a three-phase balanced star-connected load is essential for correctly identifying the potential of the neutral point. In such a system, the neutral point is at 0 V with respect to the ground due to the balanced nature of the load, where the vector sum of the currents at the neutral point is zero. This makes the correct option 1, which states that the potential of the neutral point is 0 V.