Recent Trends in Power System Stability: Recent Trends in Power System Stability – Recent trends in design of large alternators tend towards lower short circuit ratio (SCR = 1/Xd), which is achieved by reducing machine air gap with consequent savings in machine mmf, size, weight and cost. Reduction in the size of rotor reduces inertia […]

### POWER SYSTEM STABILITY

## Some factors affecting Transient Stability

Some factors affecting Transient Stability: Some factors affecting Transient Stability – The two-machine system can be equivalently reduced to a single machine connected to infinite bus bar. The qualitative conclusions regarding system stability drawn from a two-machine or an equivalent one-machine infinite bus system can be easily extended to a multimachine system. In the last […]

## Numerical Solution of Swing Equation

Numerical Solution of Swing Equation: Numerical Solution of Swing Equation – In most practical systems, after machine lumping has been done, there are still more than two machines to be considered from the point of view of system stability. Therefore, there is no choice but to solve the swing equation of each machine by a […]

## Equal Area Criterion

Equal Area Criterion: Equal Area Criterion – In a system where one machine is swinging with respect to an infinite bus, it is possible to study transient stability by means of a simple criterion, without resorting to the numerical solution of a swing equation. Consider the swing equation If the system is unstable δ continues […]

## Transient Stability

Transient Stability: Transient Stability – It has been shown in Sec. 12.4 that the dynamics of a single synchronous machine connected to infinite bus bars is governed by the nonlinear differential equation where As said earlier, this equation is known as the swing equation. No closed forrr solution exists for swing equation except for the […]

## Steady State Stability

Steady State Stability: The steady state stability limit of a particular circuit of a power system is defined as the maximum power that can be transmitted to the receiving end without loss of synchronism. Consider the simple system of Fig. 12.14 whose dynamics is described by equations and For determination of steady state stability, the […]

## Simple System

Simple System: Simple System – Machine Connected to Infinite Bus Figure 12.14 is the circuit model of a single machine connected to infinite bus through a line of reactance Xe. In this simple case From Eq. (12.29b) The dynamics of this system are described in Eq. (12.11) as Two Machine System The case of two […]

## Node Elimination Technique

Node Elimination Technique: Node Elimination Technique – In stability studies, it has been indicated that the buses to be considered are those which are excited by the internal machine voltages (transient emf s) and not the load buses which are excited by the terminal voltages of the generators. Therefore, in YBUS formulation for the stability […]

## Power Angle Equation

Power Angle Equation: Power Angle Equation – In solving the swing equation (Eq. (12.10)), certain simplifying assumptions are usually made. These are: Mechanical power input to the machine (Pm) remains constant during the period of electromechanical transient of interest. In other words, it means that the effect of the turbine governing loop is ignored being […]

## Dynamics of a Synchronous Machine

Dynamics of a Synchronous Machine: Dynamics of a Synchronous Machine – kinetic energy of the rotor at synchronous machine is where But where where We shall define the inertia constant H such that where It immediately follows that M is also called the inertia constant. Taking G as base, the inertia constant in pu is […]

## Introduction to Power System Stability

Introduction to Power System Stability: Introduction to Power System Stability – The stability of an interconnected power system is its ability to return to normal or stable operation after having been subjected to some form of disturbance. Conversely, instability means a condition denoting loss of synchronism or falling out of step. Stability considerations have been […]