Faults

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

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 \(I_a\).

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 10 kVA, 110 V, 3-phase, 4-wire, 60 Hz alternator generates 70 volts per phase when excited to give rated voltage at full load. The armature synchronous impedance per phase is 0.2 ohm. What is the current in each phase if the generator terminals are short-circuited?

emergency 3-phase generator, 3-wire GM generator is rated 350 kVA, 460 volts, 60 Hz, with a reactance of 8%. Solve for the symmetrical 3-phase short circuit.

In an electric system the available short circuit MVA is 600 MVA. What is the Thevenin’s equivalent reactance at 34.5 kV?

A balanced delta connected load draws 100 A line current from a balanced 3 phase supply. Determine the zero sequence components of the currents.

A 150 MVA, 13.8 kV, Y-connected, \(3\Phi\), 60 Hz alternator is operating at rated voltage and at no load when a three phase fault occurs at its terminals. If the subtransient reactance of the alternator is j0.2 pu, calculate the current at the instant the fault occurs.

In an electric system the available short-circuit MVA is 600 MVA. What is the Thevenin’s equivalent reactance at 34.5 kV?

A generator rated 600 kVA, 2,400 V, 60 Hz, 3-phase, 6-poles and wye-connected has 10% synchronous reactance. If a three-phase fault occurs at its terminals, what will be the short-circuit current?

When a line to ground faults occurs, the current in a faulted phase is 100 A. What is the zero sequence current in this case?

The positive, negative and zero sequence reactances of a 20-MVA, 13.2 kV synchronous generator are 0.3 pu, 0.2 pu and 0.1 pu, respectively. The generator is solidly grounded and is not loaded. A line to ground fault occurs on phase a. Neglecting all resistances, determine \(I_{a1}\).

A generator rated 600 KVA, 2,400 v, 60 HZ , 3-phase, 6-poles and wye- connected has 10% synchronous reactance. If a three-phase fault occurs, what will be the short circuit current?

The per unit impedance of a circuit element is 0.30. If the base KV and base MVA are halved, then the new value of the per unit impedance of the circuit element will be,

The reactance of a generator designated “X” is given as 0.25 per unit based on the generator’s nameplate rating of 18 kV, 500 MVA. The base for calculation is 20 kV, 100 MVA. Find “X” on the new base.

What is the equivalent of \(a^2 + a + j\), where \(a = 1\angle 120^\circ\)?

When a line to ground fault occurs, the current in a faulted phase is 100A. The zero sequence current in the case will be

For a single line to ground fault the zero sequence current is given by j3.0pu. The current carried by the neutral during the fault is