Question

Repeat Problem 9.24 for a bolted line-to-line fault.

Short answer

The value of sub transient fault current is$\left[\begin{array}{c}0\\ 2.43\angle 180°\\ 2.43\angle 0°\end{array}\right]perunit$and$\left[\begin{array}{c}0\\ 14.03\angle 180°\\ 14.03\angle 0°\end{array}\right]kA$.

The value of contributions to the fault current from each generator is$\left[\begin{array}{c}j0.0092\\ 1.502\angle -179.8°\\ 1.502\angle -0.2°\end{array}\right]perunit$and $\left[\begin{array}{c}3.463\angle -90°\\ 1.731\angle 89.4\\ 1.731\angle 90.6°\end{array}\right]kA$

The value of contributions to the fault current from each transformer is

The value of contributions to the fault current from each transformer is$\left[\begin{array}{c}-j0.011\\ 0.925\angle 179.66°\\ 0.925\angle 0.34°\end{array}\right]perunit$and$\left[\begin{array}{c}4.932\angle -90°\\ 1.731\angle -90.6°\\ 1.731\angle -89.4°\end{array}\right]kA$

Step-by-step solution

Write the given data from the question.

The circuit zero sequence impedance is$Z_0$.

The positive sequence impedance of the circuit is$Z_1$.

The negative sequence impedance of the circuit is $Z_2$.

$I_0$Is the zero sequence current flowing through zero sequence impedance$Z_0$.

$I_1$Is the positive sequence current flowing through positive impedance $Z_1$.

$I_2$Is the negative sequence current flowing through negative sequence impedance $Z_2$.

$I_{a,}{I}_b$, and $I_c$are phase currents.

$V_F$Is the pre-fault bus voltage in the positive-sequence network.

Determine the formula of per unit reactance of generator, motor and neutral reactor.

Write the formula of sub transient fault current.