Trends in Voltage Stability: Trends in Voltage Stability – The present day transmission networks are getting more and more stressed due to economic and environmental constraints. The trend is to operate the existing networks optimally close to their loadability limit. This consequently means that the system operation is also near voltage stability limit (nose point) […]

### MODERN POWER SYSTEM

## Prevention of Voltage Collapse

Prevention of Voltage Collapse: Prevention of Voltage Collapse is given by Application of reactive power-compensating devices. Adequate stability margins should be ensured by proper selection of compensation schemes in terms of their size, ratings and locations. Control of network voltage and generator reactive output Several utilities in the world such as EDF (France), ENEL (Italy) […]

## Voltage Stability Analysis

Voltage Stability Analysis: The voltage stability analysis for a given system state involves examining following two aspects. Proximity to voltage instability: Distance to instability may be measured in terms of physical quantities, such as load level, real power flow through a critical interface, and reactive power reserve. Possible contingencies, such as a line outage, loss […]

## Mathematical Formulation of Voltage Stability

Mathematical Formulation of Voltage Stability: Mathematical Formulation of Voltage Stability – The slower forms of voltage instability are normally analysed as steady state problems using power flow simulation as the primary study method. “SnapÂshots” in time following an outage or during load build up are simulated. Besides these post-disturbance power flows, two other power flow […]

## Voltage Stability

Voltage Stability: Voltage Stability – Voltage control and stability problems are very much familiar to the electric utility industry but are now receiving special attention by every power system analyst and researcher. With growing size along with economic and environmental pressures, the possible threat of voltage instability is becoming increasingly pronounced in power system networks. […]

## Long Term Load Prediction

Long Term Load Prediction Using Econometric Models: Long Term Load Prediction – If the load forecasts are required for planning purposes, it is necessary to select the lead time to lie in the range of a few months to a few years. In such cases, the load demand should be decomposed in a manner that […]

## Kalman Filtering Approach

Kalman Filtering Approach: Kalman Filtering Approach – The time series approach has been widely employed in dealing with the load forecasting problem in view of the relative simplicity of the model forms. However, this method tends to ignore the statistical information about the load data which may often be available and may lead to improved […]

## Estimation of Time Series Prediction

Estimation of Time Series Prediction: Estimation of Time Series Prediction – If yd(k) is subtracted from the sequence y(k), the result would be a sequence of data for the stochastic part of the load. We have to identify the model for ys (k) and then use it to make the prediction ys(k+j). A convenient method […]

## Estimation Techniques of Periodic Components

Estimation Techniques of Periodic Components: Estimation Techniques of Periodic Components — The deterministic part of the load may contain some periodic components in addition to the average and the polynomial terms. Consider for example the curve shown in Fig. 16.2 which gives the variation of the active power supplied by a power utility over a […]

## Estimation of Average and Trend Terms

Estimation of Average and Trend Terms: Estimation of Average and Trend Terms – The simplest possible form of the deterministic part of y(k) is given by where yd represents the average or the mean value of yd(k), bk represents the `trend’ term that grows linearly with k and e(k) represents the error of modelling the […]

## Forecasting Methodology

Forecasting Methodology: Forecasting Methodology may be divided into three broad classes. Techniques may be based on extrapolation or on correlation or on a combination of both. Techniques may be further classified as either deterministic, probabilistic or stochastic. Extrapolation Extrapolation techniques involve fitting trend curves to basic historical data adjusted to reflect the growth trend itself. […]

## Introduction to Load Forecasting Technique

Introduction to Load Forecasting Technique: Introduction to Load Forecasting Technique – Load forecasting plays an important role in power system planning, operation and control. Forecasting means estimating active load at various load buses ahead of actual load occurrence Planning and operational applications of load forecasting requires a certain ‘lead time’ also called forecasting intervals. Nature […]

## Facts Controllers

Facts Controllers: The development of FACTS controllers has followed two different approaches. The first approach employs reactive impedances or a tap changing transformer with thyristor switches as controlled elements, the second approach employs self-commutated static converters as controlled voltage sources. In general, FACTS controllers can be divided into four categories. (i) series (ii) shunt (iii) […]

## Principle Operation of Converters

Principle Operation of Converters: Principle Operation of Converters – Controllable reactive power can’be generated by dc to ac switching converters which are switched in synchronism with the line voltage with which the reactive power is exchanged. A switching power converter consists of an array of solid-state switches which connect the input terminals to the output […]

## Flexible AC Transmission Systems

Flexible AC Transmission Systems: Flexible AC Transmission Systems – The rapid development of power electronics technology provides exciting opportunities to develop new power system equipment for better utilization of existing systems. Since 1990, a number of control devices under the term FACTS technology have been proposed and implemented. FACTS devices can be effectively used for […]

## Comparison Between Statcom and SVC

Comparison Between Statcom and SVC: Comparison Between Statcom and SVC – It may be noted that in the normal linear operating range of the V-I characteristic and functional compensation capability of the STATCOM and the SVC are similar. However, the basic operating principles of the STATCOM, which, with a converter based var generator, functions as […]

## Shunt Compensations

Shunt Compensations: Shunt Compensations are connected in shunt at various system nodes (major substations) and sometimes at mid-point of lines. These serve the purposes of voltage control and load stabilization. As a result of installation of shunt compensators in the system, the nearby generators operate at near unity pf and voltage emergencies mostly do not […]