Analyzing L-G, L-L, and L-L-G Faults Using Sequence Networks

This assignment solution details the analysis of unsymmetrical faults in a 100 MVA, 50 Hz star-connected generator supplying a 22 kV feeder line. It focuses on line-to-ground (L-G), line-to-line (L-L), and line-to-line-to-ground (L-L-G) faults. The solution employs the method of sequence components to determine fault currents and phase voltages under various fault conditions. It includes calculations for positive, negative, and zero sequence reactances, pre-fault and post-fault voltage sequence components, and phase voltages. The document provides a step-by-step approach to calculating fault currents and analyzing the impact of each type of fault on the power system. Desklib offers a range of similar solved assignments and past papers to aid students in their studies.

UNSYMMETRICAL FAULTS
3.2
The following, 100 MVA, 50 Hz star connected generator supplies a 22 Kv feeder line, the line
to ground fault is taken in between feeder, therefore we consider positive, negative and zero
sequence components.
Determine the line reactance ohmic value to p.u. values.
The reactance of positive sequence component has shown in figure 1.
Determine the equivalent reactance of a circuit.
Determine the negative sequence line reactance ohmic value to p.u. values.
The reactance of positive sequence component has shown in figure 2.
Determine the negative sequence equivalent reactance of a circuit.
Determine the zero sequence line reactance ohmic value to p.u. values.
The reactance of positive sequence component has shown in figure 3.
Determine the zero sequence equivalent reactance of a circuit.

a)
Determine the phase A short circuited or Line to ground fault by using of sequence circuit
method. The following line to ground (L-G) fault has shown in figure 1-a.
During fault conditions:
Hence, the positive sequence and zero sequence pre fault voltage is zero.
The symetricl componet to get the fault analysis.
(1)
Determine the p.u. sequence componets of ;
(2)
Determine The p.u. voltage sequence component .
The postive sequence pre fault voltage as shown in figure 1-a.
The neagatve sequence prefault voltage as shown in figure 1-a.
The zero sequence prefault voltage as shown in figure 1-a.
3)
Determine the phase voltge .
Determine the value of
Determine the value of

Determine the fault curent
(b)
Determine the phase B and C short circuited or Line to line fault by using of sequence circuit
method. The following line to ground (L-L) fault has shown in figure 2-a.
During fault conditions:
Hence, the positive sequence and zero sequence pre fault voltage is zero.
Determine the p.u. sequence componets of ;
(2)

Determine The p.u. voltage sequence component .
The postive sequence pre fault voltage as shown in figure 2-b.
The neagatve sequence prefault voltage as shown in figure 1-b.
3)
Determine the phase voltge .
Determine the value of
(4)
Determine the fault curent
c)
Determine the phase B and C short circuited or Line to line ground fault by using of sequence
circuit method. The following line to ground (L-L-G) fault has shown in figure 1-C.
During fault conditions:
Hence, the positive sequence and zero sequence pre fault voltage is zero.
Determine the p.u. sequence componets of ;

Detwermine the
2)
Determine The p.u. voltage sequence component .
The postive sequence pre fault voltage as shown in figure 1-c.
The neagatve sequence prefault voltage as shown in figure 1-c.
The zero sequence prefault voltage as shown in figure 1-c.
Determine the phase voltge .
(3)
Determine the value of
Determine the value of
(4)
Determine the fault curent