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Option A: The negative and zero sequence voltages are maximum at the fault point and decrease towards the neutral

Explanation & Concepts:
In an unsymmetrical fault condition, the negative and zero sequence voltages are maximum at the point of the fault because the network impedances for these sequences are lowest at that location. As we move away from the fault point towards the generator neutral, the sequence impedances increase, causing the sequence voltages to decrease.

Working Principle: During an unsymmetrical fault, the fault location acts as a source of negative and zero sequence currents. According to Thevenin's theorem for sequence networks, the sequence voltage at any point is $V_x = I_{sequence} 	imes Z_{x(to\ neutral)}$, where $Z_{x(to\ neutral)}$ is the impedance from the fault to the neutral. Since the impedance is zero at the neutral point and maximum at the fault point (effectively the full sequence impedance of the network), the sequence voltage follows a gradient peaking at the fault.

Key Formulas: $V_{2} = I_{2} Z_{2}$ — Negative sequence voltage drop; $V_{0} = I_{0} Z_{0}$ — Zero sequence voltage drop

Key Points: Negative and zero sequence networks are passive networks relative to the fault point.; The neutral point is the reference (zero potential) for sequence voltages.; Fault impedance governs the distribution of sequence currents and voltages.; Sequence voltages are essential for calculating unbalanced fault currents.

Advantages: Enables systematic analysis of unsymmetrical faults using sequence components.; Simplifies complex 3-phase circuits into independent single-phase networks.

Disadvantages: Requires complex impedance calculation for different sequence networks (Z1, Z2, Z0).; Requires knowledge of mutual coupling, especially for zero-sequence networks.

Applications: Relay coordination and settings calculation.; Determination of fault currents in power system planning.

Additional Info: The zero-sequence network is highly dependent on the grounding configuration of the system transformers.. Option B is incorrect because it describes the inverse relationship; voltages increase with distance from the neutral, not towards it.

Answer: A is correct — The negative and zero sequence voltages are maximum at the fault point and decrease towards the neutral due to the sequence impedance distribution.

Exam Tip: Always remember that sequence impedances are measured from the neutral to the point of fault; thus, zero impedance at the neutral implies zero voltage contribution from that terminal.

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Option B: The negative and zero sequence voltages are Minimum at the fault point and increase towards the neutral

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Option C: The negative sequence is maximum and zero sequence minimum at the fault point and decrease and increase respectively towards the neutral

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Option D: None of the above

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