If the positive, negative and zero sequence reactances of an element of a power system are 0.3, 0.3 and 0.8 re

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If the positive, negative and zero sequence reactances of an element of a power system are 0.3, 0.3 and 0.8 respectively, then the element would be a

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Option D: Transmission line

Explanation & Concepts:
Given: Positive sequence reactance X1 = 0.3 pu, Negative sequence reactance X2 = 0.3 pu, Zero sequence reactance X0 = 0.8 pu.

Formula Used: $$X_1 = X_2 
eq X_0$$

Steps: Analyze Component Reactances: In power systems, static elements like transmission lines and transformers are symmetrical and passive. For these, the positive and negative sequence impedances are equal because the path taken by the currents is the same regardless of the phase sequence.. Evaluate Sequence Characteristics: For a transmission line, the zero-sequence reactance $X_0$ is significantly different (usually higher due to mutual coupling between phases and ground return path) from the positive and negative sequence reactances. Rotating machines (generators/motors) typically have distinct sub-transient and transient reactances, and their sequence reactances are generally not equal.. Conclusion: Given $X_1 = 0.3$, $X_2 = 0.3$, and $X_0 = 0.8$, the condition $X_1 = X_2$ holds true while $X_0$ is distinct, which is the characteristic behavior of a static transmission line.

Answer: D is correct because for static elements like transmission lines, the positive and negative sequence reactances are equal ($X_1 = X_2$), while the zero-sequence reactance differs due to the ground return path.

Exam Tip: Remember that for all static components (lines, transformers), $X_1 = X_2$. For rotating machines, $X_1$ is usually the transient or sub-transient reactance and $X_2

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Option A: Synchronous generator

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Option B: Synchronous motor

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Option C: Static load

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