Faults

In symmetrical components, what is the vector sum of \(1 + a + a^2\)?

If the load of a wye-connected transformer are:
\(I_a = 10\text{ cis }(-30^\circ)\)
\(I_b = 12\text{ cis }215^\circ\)
\(I_c = 15\text{ cis }82^\circ\)
What is the phase b positive sequence component?

Given three unbalanced three-phase voltages:
\(V_a = 150 + j0\text{ V}\)
\(V_b = -90 - j120\text{ V}\)
\(V_c = -120 + j90\text{ V}\)
Determine \(V_{a1}\).

The three-phase unbalanced currents are:
\(I_a = 10\text{ cis }(-30^\circ)\)
\(I_b = 0\)
\(I_c = 10\text{ cis }150^\circ\)
Find the negative sequence current of phase a.

Given the following currents:
\(I_a = 60 + j0\text{ A}\)
\(I_b = -36 - j48\text{ A}\)
\(I_c = -48 + j36\text{ A}\)
Solve for the negative sequence component of \(I_a\).

The three-phase unbalance currents are:
\(I_a = 10\text{ cis }(-30^\circ)\)
\(I_b = 0\)
\(I_c = 10\text{ cis }150^\circ\)
Find the zero sequence current.

Given the following currents:
\(I_a = 60 + j0\text{ A}\)
\(I_b = -36 - j48\text{ A}\)
\(I_c = -48 + j36\text{ A}\)
Solve for zero sequence component of \(I_a\).

The sequence currents of phase a current are as follows:
Zero sequence current = \(14.13 \angle 17.34^\circ\)
Positive sequence current = \(2.98 \angle 10.06^\circ\)
Negative sequence current = \(708.26 \angle -31^\circ\)
Determine phase a current.

The sequence components of phase a current are:
Zero sequence component = \(0.47 + j1.49\)
Positive sequence component = \(18.4\text{ cis }(-31.6^\circ)\)
Negative sequence component = \(3.23\text{ cis }168.2^\circ\)
Determine the phase b current.

The sequence components of phase a current are:
Zero sequence = \(0.47 + j1.49\)
Positive sequence = \(18.4\text{ cis }(-31.6^\circ)\)
Negative sequence = \(3.23\text{ cis }168.2^\circ\)
Determine the phase c current.

Determine the symmetrical components of the line current in line 'a' if one of the in phase impedance of its delta-connected load connected across lines 'ca' is removed. The delta load with impedance of \(10 \angle 0^\circ\) ohms per phase is supplied from a 220 volts, 60 cycle, 3-phase. Assume a phase sequence of a-b-c.

A star-connected balanced load takes 75 A from a balanced 3-phase, 4-wire supply. If the two supply lines of the fuses are removed determine the symmetrical components of the line currents after the fuses are removed.

A 50 MVA, 33 kV/11 kV, three-phase, wye-delta connected transformer has a 3% impedance. What is the percent impedance at 100 MVA base and 34.5 kV base?

At a certain location of an electrical system, the available short circuit MVA is 10 at 110 kV while its Thevenin's equivalent reactance is 0.05 pu. Determine the per unit reactance of this point using a base 20 MVA and 115 kV?

A 13.8 kV/440 V, 50 kVA single-phase transformer has a leakage reactance of 300 ohms referred to the 13.8 kV side. Determine the per unit value of the leakage reactance for the voltage base.

A 5 kVA, 2400-120/240 volt distribution transformer when given a short circuit test had 94.2 volts applied with rated current flowing in the short-circuited wiring. What is the per unit impedance of the transformer?

A 3-phase, 375 kVA, 480 V, 50 Hz, wye connected alternator has an equal positive and negative sequence reactance of 10%. Find the symmetrical fault current, if a 3-phase fault occurs at the alternator terminals.

A generator rated 600 kVA, 2400 V, 60 cycles, 3-phase, 6-poles and wye-connected has 10% synchronous reactance. If a three-phase fault occurs, what will be the short circuit current?

A 20 MVA, 13.8 kV, 60 Hz, three-phase synchronous turbo alternator has a positive, negative and zero sequence reactances of 0.25, 0.35 and 0.15 respectively. If lines b and c are short-circuited, determine the subtransient fault current in line b. Assume the alternator is operating at no load and at rated voltage with the neutral of the alternator solidly grounded.

At a certain location in an electric system, the available fault MVA is 400 MVA. A 15 MVA, 34.5 kV/6.24 kV, 2.5% impedance, wye-wye grounded transformer is installed at that location. Determine the short circuit MVA at the secondary side of the transformer.