What is the magnitude of initial symmetrical rms current in the breakers when a three-phase short circuit fault occurs?
The magnitude of initial symmetrical rms current in the breakers during a three-phase short circuit fault can be calculated using the sub-transient reactance, transient reactance, and synchronous reactance of the generator.
Calculation of Initial Symmetrical RMS Current
The magnitude of initial symmetrical rms current in the breakers during a three-phase short circuit fault can be determined using the reactance values provided for the generator. The sub-transient reactance (X"), transient reactance (X'), and synchronous reactance are crucial parameters in calculating the current.
Impedance Calculation:
To determine the total impedance (Z) during the fault, we can use the formula:
Z = X" + X'
Substitute Given Values:
Substituting the given values:
X" = 0.19
X' = 0.26
Calculate Total Impedance:
Z = 0.19 + 0.26
Z = 0.45
Current Calculation:
Using the formula I = V / Z, where:
I = current
V = rated voltage of the generator (11 kV)
Substitute Values and Solve:
I = 11,000 / 0.45
I = 24,444 A
Therefore, the magnitude of the initial symmetrical rms current in the breakers during a three-phase short circuit fault is 24,444 amperes.