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 […]
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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
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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
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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
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Types of Unsymmetrical faults in Power System: There are two types of unsymmetrical faults in power system namely, 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
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Construction of Sequence Network in Power System: Before sections the Sequence Network of various Power System elements synchronous machines, transformers and lines have been given. Using these, the Construction of Sequence Network in Power System can be explained. To start with, the positive Sequence Network in Power System is constructed by examination of the one-line
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Sequence Impedance and Networks of Transformers: It is well known that almost all present day installations have three-phase transformers since they entail lower initial cost, have smaller space requirements and higher efficiency. The positive sequence series impedance of a transformer equals its leakage impedance. Since a transformer is a static device, the leakage impedance does
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Zero Sequence Impedance of Transmission Line: Zero Sequence Impedance of Transmission Line – A fully transposed three-phase line is completely symmetrical and therefore the per phase impedance offered by it is independent of the phase sequence of a balanced set of currents. In other words, the Sequence Impedance of Transmission Line offered by it to
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Sequence Impedances and Networks of Synchronous Machine: Sequence Impedances and Networks of Synchronous Machine – Figure 10.11 depicts an unloaded synchronous machine (generator or motor) grounded through a reactor (impedance Zn). Ea, Eb and Ec are the induced emfs of the three phases. When a fault (not shown in the figure) takes place at machine terminals,
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Sequence Impedances of Transmission Lines: Sequence Impedances of Transmission Lines – Figure 10.9 shows the circuit of a fully transposed line carrying unbalanced currents. The return path for In is sufficiently away for the mutual effect to be ignored. Let Xs = self reactance of each line Xm = mutual reactance of any line pair
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