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SarkariResultOutBMS · 2024

Previous Year Question

In a power flow study of a big power system, the YBUS matrix is
  1. Null matrix
  2. Sparse matrix
  3. Full matrix
  4. Unity matrix

Correct answer: B

Explanation

Each power-system bus is directly connected to only a small fraction of all other buses. Therefore most off-diagonal elements of the bus-admittance matrix are zero, making YBUS a sparse matrix for a large network. Hence option B.

Formula

Yij=0 when buses i and j have no direct branch connection

Step-by-step solution

Sparsity of YBUS explanatory diagram

Correct Answer

B — Sparse matrix

Concept and Reasoning

Each power-system bus is directly connected to only a small fraction of all other buses. Therefore most off-diagonal elements of the bus-admittance matrix are zero, making YBUS a sparse matrix for a large network. Hence option B.

Calculation / Key Relation

Yij=0 when buses i and j have no direct branch connection

Exam Takeaway

Large power-network YBUS is sparse because connectivity is local.

Common Mistake

Do not call YBUS full merely because every bus participates in the system solution.

Common mistake

Do not call YBUS full merely because every bus participates in the system solution.

Exam tip

Large power-network YBUS is sparse because connectivity is local.

Quick method

Large power-network YBUS is sparse because connectivity is local.