The figure shown represents a/an:

The figure shown represents a positive sequence.

Definition: A positive sequence is a balanced three-phase system in which the three-phase voltages or currents are equal in magnitude, displaced by 120° electrically, and follow the natural order of phase sequence (i.e., A → B → C). In a positive sequence, the phase relationship among the three components ensures that the system operates smoothly and efficiently under ideal balanced conditions.

Working Principle:

In electrical power systems, the three-phase components of voltage or current can be decomposed into three symmetrical components:

• Positive Sequence: The three components are equal in magnitude and displaced by 120° in the natural order (A → B → C).
• Negative Sequence: The three components are equal in magnitude and displaced by 120° but in the reverse order (A → C → B).
• Zero Sequence: All three components have the same magnitude and are in phase with one another.

A positive sequence represents the normal operating condition of a balanced three-phase system, where the system is free from any imbalance or distortion. This sequence is responsible for delivering power effectively to loads in a balanced and stable manner.

Advantages:

• Ensures efficient power transfer to balanced loads.
• Minimizes losses and disturbances in the system.
• Maintains the stability and reliability of the power system.

Applications:

• Used in balanced three-phase power systems for the generation, transmission, and distribution of electrical energy.
• Critical for the operation of three-phase motors and generators, which rely on a balanced supply for smooth and efficient operation.

Correct Option Analysis:

The correct option is:

Option 1: Positive sequence.

This option correctly identifies the characteristics of the figure shown. A positive sequence ensures that the three-phase system is balanced, with voltages or currents equal in magnitude and displaced by 120° in their natural order (A → B → C).

Additional Information

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

Option 2: Negative sequence.

This option is incorrect because a negative sequence refers to a situation where the three-phase voltages or currents are equal in magnitude but displaced by 120° in the reverse order (A → C → B). Negative sequence components are typically caused by unbalanced loads or faults in the system and result in undesirable effects such as heating in rotating machines.

Option 3: Zero sequence.

Zero sequence components occur when the three-phase voltages or currents are equal in magnitude and in phase with one another. This situation is common during ground faults or unbalanced conditions involving a neutral conductor. However, it does not represent the balanced operation of a three-phase system, as shown in the figure for positive sequence.

Option 4: Unbalanced network.

While an unbalanced network refers to a system where the three-phase voltages or currents are not equal in magnitude or are not displaced by 120°, it is not the correct representation of the figure shown. The figure represents a balanced positive sequence, not an unbalanced network.

Conclusion:

Understanding the symmetrical components of three-phase systems is essential for analyzing and diagnosing power system conditions. A positive sequence, as explained, represents a balanced system where voltages or currents are equal in magnitude and displaced by 120° in their natural order. This condition is vital for the efficient and reliable operation of three-phase power systems and equipment.