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Examoogle • User • info@examoogle.com • EE-2024-8821
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If system reactive power is 1 MVAR and short circuit capacity is 81.34 MVA/phase then the ratio of receiving end to sending end voltage is
0.99
0.88
0.89
0.90
0.99
Quick Summary: Given: System reactive power Q = 1 MVAR, Short circuit capacity S_sc = 81.34 MVA/phase.
System reactive power Q = 1 MVAR, Short circuit capacity Ssc = 81.34 MVA/phase.
Q=XVs2−VsVr=XVs(Vs−Vr),Ssc=XVs2⟹VsVr=1−SscQ
Identify Relationship
The change in voltage due to reactive power flow in a system is related to the short circuit capacity (Ssc). The voltage drop can be approximated using the ratio of reactive power to short circuit capacity.
VsVs−Vr≈SscQ
Rearrange for Ratio
We need the ratio of receiving end voltage (Vr) to sending end voltage (Vs). Rearranging the approximation formula gives:
VsVr=1−SscQ
Substitute Values
Substitute Q=1 MVAR and Ssc=81.34 MVA/phase into the equation.
VsVr=1−81.341
Calculate Final Result
Performing the division 1/81.34≈0.0123, then subtracting from 1.
VsVr≈1−0.0123=0.9877≈0.99
A is correct because the ratio of receiving end to sending end voltage, calculated as 1−(Q/Ssc), yields approximately 0.99.
This concept is a cornerstone of Power System Analysis, specifically in understanding grid strength; a higher short circuit capacity implies a 'stiffer' grid with less voltage fluctuation.