**AIM:**

To become familiar with modelling and analysis of power systems under faulted condition and

to compute the fault level, post-fault voltages and currents for different types of faults, both

symmetric and unsymmetric.

**SOFTWARE REQUIRED:**

MATLAB 5.3

**THEORY:**

**PROCEDURE:**

1. Enter the command window of the MATLAB.

2. Create a new M – file by selecting File - New – M – File

3. Type and save the program.

4. Execute the program by either pressing Tools – Run.

View the results.

EXERCISE:

EXERCISE:

The one line diagram of a simple power system is shown in figure. The neutral of each

generator is grounded through a current limiting reactor of 0.25/3 per unit on a 100MVA base.

The system data expressed in per unit on a common 100 MVA base is tabulated below. The

generators are running on no load at their rated voltage and rated frequency with their emfs in

phase.

Determine the fault current for the following faults.

(a) A balanced three phase fault at bus 3 through a fault impedance Zf = j0.1 per unit.

(b) A single line to ground fault at bus3 through a fault impedance Zf = j0.1 per unit.

(c) A line to line fault at bus3 through a fault impedance Zf = j0.1 per unit.

(d) A double line to ground fault at bus3 through a fault impedance Zf = j0.1 per unit.Verify the result using MATLAB program.

**PROGRAM:**

zdata1 = [0 1 0 0.25

0 2 0 0.25

1 2 0 0.125

1 3 0 0.15

2 3 0 0.25];

zdata0 = [0 1 0 0.40

0 2 0 0.10

1 2 0 0.30

1 3 0 0.35

2 3 0 0.7125];

zdata2 = zdata1;

Zbus1 = zbuild(zdata1)

Zbus0 = zbuild(zdata0)

Zbus2 = Zbus1;

symfault(zdata1,Zbus1)

lgfault(zdata0, Zbus0, zdata1, Zbus1, zdata2, Zbus2)

llfault(zdata1, Zbus1, zdata2, Zbus2)

dlgfault(zdata0, Zbus0, zdata1, Zbus1, zdata2, Zbus2)

**RESULT:**

Finally, became familiar with modelling and analysis of power systems under faulted condition and

to compute the fault level, post-fault voltages and currents for different types of faults, both

symmetric and unsymmetric.

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