# Unsymmetrical Fault Analysis

## Unsymmetrical Fault Analysis:

Bus Impedance Matrix Method : Bus Impedance Matrix Method for Analysis of Unsymmetrical Shunt Faults: Bus Impedance Matrix Method of fault analysis, given for symmetrical faults  can be easily extended to the case of unsymmetrical faults. Consider for example an LG fault on the rth bus of a n-bus system. The connection of sequence networks to simulate the fault is shown in Fig. 11.25. The positive sequence …

Double Line to Ground Fault (LLG): Figure 11.9 shows a Double Line to Ground Fault at F in a power system. The fault may in general have an impedance Zf as shown. The current and voltage (to ground) conditions at the fault are expressed as The symmetrical components of voltages are given by from which it follows that From Eqs. (11.22a) and (11.22b) From Eqs. (11.19), …

Line to Line Fault (LL): Figure 11.7 shows a Line to Line Fault at F in a power system on phases b and c through a fault impedance Zf. The phases can always be relabelled, such that the fault is on phases b and c. The currents and voltages at the fault can be expressed as The symmetrical components of the fault currents are from …

Open Conductor Faults : An open conductor faults is in series with the line. Line currents and series voltages between broken ends of the conductors are required to be determined. Figure 11.19 shows currents and voltages in an open conductor fault. The ends of the system on the sides of the fault are identified as F, F′, while the conductor ends are identified …

Single Line to Ground Fault : Figure 11.4 shows a Single Line to Ground Fault at F in a power system through a fault impedance Zf. The phases are so labelled that the fault occurs on phase a. At the fault point F, the currents out of the power system and the Single Line to Ground Fault are constrained as follows: The symmetrical components of the …

Symmetrical Component Analysis of Unsymmetrical Faults : Symmetrical Component Analysis of Unsymmetrical Faults – Consider a general power network shown in Fig. 11.1. It is assumed that a shunt type fault occurs at point F in the system, as a result of which currents Ia, Ib, Ic flow out of the system, and Va, Vb, Vc are voltages of lines a, b, …

Unsymmetrical Fault Types : Various Unsymmetrical Fault Types that occur in power systems are: Shunt Type Fault: Single Line to Ground Fault (LG) Line to Line Fault (LL) Double Line to Ground Fault (LLG) Series Type Fault: (i) Open conductor (one or two conductors open) fault. It was stated, that a three-phase (3L) fault being the most severe must be used to calculate the rupturing capacity of circuit breakers, …