Faults

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 the resistances, determine the fault current.

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.

The sequence components of the line A current are as follows: \(I_{a0} = 14.13\angle 17.34^\circ\) A, \(I_{a1} = 708.26\angle -31^\circ\) A and \(I_{a2} = 2.98\angle 10.06^\circ\) A. Find the line current \(I_b\) in amperes.

In a short circuit analysis, the positive, negative, and zero sequence impedances are 0.20 pu, 0.20 pu, and 0.25 pu, respectively, using a base MVA of 50. Estimate the fault current on the faulted lines if a line to line fault at the 138 kV level occurs.

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

In a 13.8 kV, 10 MVA base three phase system, a phase to phase fault occurs. If the Thevenin’s equivalent impedance of the system is 2.63%, what is the magnitude of the fault current?

The three unbalanced currents are \(I_a = 10\ \text{cis}\ (-30^\circ)\), \(I_b = 0\) and \(I_c = 10\ \text{cis}\ 150^\circ\). Find the phase C positive sequence current.

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

In which type of faults given below all the 3 components \(I_{a0}\) , \(I_{a1}\) and \(I_{a2}\) are equal?

A synchronous generator having a subtransient reactance of 0.15 pu and operating at 5 percent above its rated voltage supplies a synchronous motor having a 0.2 pu subtransient reactance. The motor is connected to the generator by a transmission line and a transformer of total reactance 0.305 pu. A sudden three-phase short circuit occurs at the generator terminals. Determine the per unit subtransient fault current.

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

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

Fault level means

A 150-MVA, 13.8-KV, Y-connected, 3ɸ, 60-HZ alternator is operating at rated voltage and at no-load when a three-phase faults occurs at its terminals. If the substransient reactance of the alternator is j0.2 pu, calculate the current the instant fault occurs.

The per unit value of a 2-ohm resistor at 100 MVA base and 10 KV base voltage is

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 calculations is 20 kV, 100 MVA. Find X” on the new base.

The line currents in amperes in phases a, b and c respectively are 500 + j150,100 – j600, and -300 + j600. Determine the zero sequence component of phase a current

There is no zero sequence component of the fault current for

At a certain point of the system network the positive, negative and zero sequence impedances are 0.25 pu, 0.25 pu, 0.3 pu, respectively. The base MVA is 100. The level at that point is 34.5 KV. Determine the zero sequence current for a one line to ground fault.

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