Unsymmetrical Fault

Unsymmetrical Fault:

Analysis of Unsymmetrical Faults : In the Analysis of Unsymmetrical Faults, the following assumptions will be made : The generated e.m.f. system is of positive sequence only. No current flows in the network other than due to fault e. load currents are neglected. The impedance of the fault is zero. Phase R shall be taken as the reference phase. In each case of Analysis of Unsymmetrical Faults, e.m.f.s’ per phase are denoted by ER,EY and EB and the terminal p.d. per phase by VR, VY and VB. Single Line to …


Sequence Impedance of Power System : Each element of power system will offer impedance to different phase sequence components of current which may not be the same. For example, the impedance which any piece of equipment offers to positive sequence current will not necessarily be the same as offered to negative sequence current or zero sequence current. Therefore, in unsymmetrical fault calculations, each piece of equipment will have three values of impedance one corresponding to each Sequence Impedance of Power System current …


Sequence Networks Unsymmetrical Faults : The analysis of an unsymmetrical fault by symmetrical components method can be conveniently done by drawing sequence networks. A Sequence Networks Unsymmetrical Faults of a particular sequence current in a given power system is the path for the flow of that sequence current in the system. It is composed of impedances offered to that sequence current in the system. Since there are three sequence currents (viz. positive sequence current, negative sequence current and zero sequence current), there will …


Unbalanced Phase Current : The Unbalanced Phase Current in a 3-phase system can be expressed in terms of symmetrical components as under : Fig. 18.6 shows the vector representation of symmetrical components. It is usually profitable in calculations to express the symmetrical components in terms of Unbalanced Phase Current. Let us express the symmetrical components of R-phase in terms of phase currents IR,IY and IB. For this purpose, express all symmetrical components of Y and B phases in terms of the symmetrical components of …


Unsymmetrical Faults on Three Power System : Those faults on the power system which give rise to unsymmetrical fault currents (i.e. unequal fault currents in the lines with unequal phase displacement) are known as Unsymmetrical Faults on Three Power System. On the occurrence of an Unsymmetrical Faults on Three Power System, the currents in the three lines become unequal and so is the phase displacement among them. It may be noted that the term `unsymmetry’ applies only to the fault itself and the …