ZBUS Formulation: ZBUS Formulation is given by By Inventing YBUS The sparsity of YBUS may be retained by using an efficient inversion technique [1] and nodal impedance matrix can then be calculated directly from the factorized admittance matrix. This is beyond the scope of this book. Current Injection Technique Equation (9.33) can be written in […]

### SYMMETRICAL FAULT ANALYSIS

## Algorithm for Short Circuit Studies

Algorithm for Short Circuit Studies: Algorithm for Short Circuit Studies – So far we have carried out short circuit calculations for simple systems whose passive networks can be easily reduced. In this section we extend our study to large systems. In order to apply the four steps of short circuit computation developed earlier to large […]

## Selection of Circuit Breakers

Selection of Circuit Breakers: Selection of Circuit Breakers – Two of the circuit breaker ratings which require the computation of SC current are: rated momentary current and rated symmetrical interrupting current. Symmetrical SC current is obtained by using subtransient reactances for synchronous machines. Momentary current (rms) is then calculated by multiplying the symmetrical momentary current […]

## Short Circuit Current Computation through Thevenin Theorem

Short Circuit Current Computation through Thevenin Theorem: Short Circuit Current Computation through Thevenin Theorem – An alternate method of computing short circuit currents is through the application of the Thevenin theorem. This method is faster and easily adopted to systematic computation for large networks. While the method is perfectly general, it is illustrated here through […]

## Short Circuit of a Loaded Synchronous Machine

Short Circuit of a Loaded Synchronous Machine: Short Circuit of a Loaded Synchronous Machine – In the previous article on the short circuit of a synchronous machine, it was assumed that the machine was operating at no load prior to the occurrence of short circuit. The analysis of short circuit on a loaded synchronous machine […]

## Short Circuit of a Synchronous Machine

Short Circuit of a Synchronous Machine(On No Load): Short Circuit of a Synchronous Machine – Under steady state short circuit conditions, the armature reaction of a synchronous generator produces a demagnetizing flux. In terms of a circuit this effect is modelled as a reactance Xa in series with the induced emf. This reactance when combined […]

## Transient on a Transmission Line

Transient on a Transmission Line: Let us consider the short circuit Transient on a Transmission Line. Certain simplifying assumptions are made at this stage. The line is fed from a constant voltage source (the case when the line is fed from a realistic synchronous machine Short circuit takes place when the line is unloaded (the […]

## Introduction to Symmetrical Fault Analysis

Introduction to Symmetrical Fault Analysis: Introduction to Symmetrical Fault Analysis devoted to abnormal system behaviour under conditions of symmetrical short circuit (symmetrical three-phase fault). Such conditions are caused in the system accidentally through insulation failure of equipment or flashover of lines initiated by a lightning stroke or through accidental faulty operation. The system must be […]