Subject: Power system analysis Electrical engineering

Preferrably handwritten solution please.

For a three phase $60$Hz electric power system shown below, supplying two loads controlled by two switchgears. Choose $13800$ V and

$50$ MVA as the base voltage and base MVA respectively at transformer $2.$

Determine the following:

a$.$ the per unit equivalent circuit including the state of the switchgears. Please include drawing of the per unit equivalent circuit.

b$.$ with SW$1$ is closed, and SW$2$ is closed, determine the real power, reactive and apparent power by the system.

c$.$ with SW$1$ is closed, and SW$2$ is open, find the overall system efficiency.

Given:

G$1$ Ratings:

Vac$=480$cis$90$

Negative sequence

$10$ MVA

R$=1\%$

X$=4\%$

T$1$ ratings:

$10$MVA

$480$V $/13800$V

R$=1\%$

X$=4\%$

Z line: $1\mathrm{.}5+$ j$10$ ohms

T$2$ Ratings:

$50$ MVA

$13800$ V $/480$ V

$\%$Z$=8\mathrm{.}944$

X$/$R$=0\mathrm{.}5$

Z$1$ ratings:

$500$cis$36\mathrm{.}87$ ohms

Z$2$ ratings:

C$=0\mathrm{.}003184$F