MGVCL Exam Paper (30-07-2021 Shift 1)
A transformer designed for operation at 60 Hz supply is working at 50 Hz supply system without changing its voltage and current ratings. Compared to the full load efficiency at 60 Hz, the full load transformer efficiency at 50 Hz.

remains unaltered
increases by 30%
increases marginally
decreases marginally

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MGVCL Exam Paper (30-07-2021 Shift 1)
The necessary equation to be solved during the load flow analysis using Fast-Decoupled methid is given below:
where B' and B'' are formed using the imaginary part of the bus admittance matrix Ybus, n is the total number of buses in the system, m is the number of voltage regulated buses. The size of matrix B' is
∆P/|Vi|= -B' ∆δ
∆Q/|Vi| = -B'' ∆|Vi|

(m-1) x (m-1)
(n-m-1) x (n-m-1)
(n-m) x (n-m)
(n-1) x (n-1)

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