Stochastic evaluation of turbine-generator shaft torsional torques

This paper presents a probabilistic approach to the evaluation of the maximum torsional torques induced in turbine-generator shafts during high-speed reclosing of system faults. In this context, investigations have been conducted on a large turbine-generator model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. The results of these investigations are presented in the form of discrete probability distributions of the maximum torsional torques induced in the turbine-generator shaft sections     

Effect of adaptive single-pole reclosing on the stochastic behaviorof turbine-generator shaft torsional torques

This paper presents a Monte Carlo based approach to evaluate of the maximum torsional torques induced in turbine-generator shafts during high-speed reclosing of system faults. Two reclosing schemes were considered, namely simultaneous and adaptive reclosing. In the case of a single line-to-ground fault, single-pole reclosing is considered in clearing such a fault. In this context, investigations have been conducted on a large turbine-generator model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. The effect of employing adaptive single-pole reclosing on the expected maximum torsional torques as well as their variances have also been investigated. A risk index which reflects the likelihood that the torque induced in a turbine-generator shaft exceeds its design value is also presented     

Probabilistic technique for sizing FACTS devices for steady-state voltage profile enhancement

A novel and simple stochastic-based approach to determine the optimal sizing of multiple flexible AC transmission systems (FACTS) devices in a power system for steady-state voltage profile enhancement is presented. In this context, investigations have been conducted on a published test system taking into consideration the uncertainty of the system load and generator scheduling. Two FACTS schemes are considered, namely a thyristor controlled series capacitor (TCSC) and two static synchronous compensators (STATCOMs) and a unified power flow controller (UPFC) and a STATCOM. The TCSC and UPFC are employed in the system to adjust the natural power sharing of two different parallel transmission lines and therefore enable the maximum transmission capacity to be utilised. Risk indices to estimate the likelihood that the voltage magnitude at a certain bus falls below a desired value is also presented.     

Stochastic evaluation of voltage sags in series capacitor compensated radial distribution systems

Voltage sags, also known as dips, are important to industrial reliability. This paper presents a Monte Carlo-based approach to evaluate the maximum voltage sag magnitudes in series capacitor compensated radial distribution systems. In this context, investigations have been conducted on a sample distribution system model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. The power system blockset of MATLAB is used in the simulation studies.     

Stochastic evaluation of transient recovery voltages across circuitbreakers of series capacitor compensated transmission lines

This paper presents a Monte Carlo based approach to evaluate the maximum transient recovery voltages induced across circuit breaker poles during clearing a fault on a series capacitor compensated transmission line. In this context, investigations have been conducted on a sample power system model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. A risk index that reflects the likelihood that the transient recovery voltage induced across circuit breaker poles exceeds its design value is also presented     

Unit commitment health analysis for interconnected systems

The concepts previously published for unit commitment and operating reserve assessment in an isolated power system using a system well-being framework are extended in this paper to evaluate unit commitment and spinning reserve requirements in interconnected power systems. The problem of interconnected power systems unit commitment is decomposed into two subproblems. Unit scheduling is first performed in each isolated power system in accordance with the specified operating criterion. This is then followed by interconnected power system evaluation. The analysis is further extended to determine the operating state probabilities for the overall interconnected power system. The paper illustrates how power system well-being is improved by interconnection with other power systems. The concepts contained in the paper are illustrated by application to two radially interconnected IEEE-RTS     

Diagnosing the health of engineering systems

System reliability evaluation can be performed using the two broad categories of deterministic and probabilistic techniques. The basic weakness associated with deterministic methods is that they do not specifically take into account the likelihood of component failures in the evaluation. There is, however, considerable reluctance to using probabilistic techniques in many engineering areas owing to the difficulty in interpreting the resulting numerical indices. An approach is presented in this paper to alleviate this difficulty by combining deterministic considerations with probabilistic indices to monitor the system well-being in the form of system health and margin states in addition to a conventional risk index. The concept of system well-being is illustrated using relatively simple network configurations. The proposed technique is also applied to a power system network to determine the degree of well-being of the various load points and the overall system. © 1997 John Wiley & Sons, Ltd.     

Effect of adaptive short time compensation on the stochasticbehavior of turbine-generator shaft torsional torques

This paper presents a Monte Carlo based approach to evaluate the maximum torsional torques induced in turbine-generator shafts during high-speed reclosing following system faults. In this context, investigations have been conducted on a large turbine-generator model taking into consideration the uncertainty of several factors associated with the practical operation of a power system. In the case of unsymmetrical faults, two switching schemes were considered in clearing and reclosing such faults, namely conventional (triple pole for line-to-line and double line-to-ground faults and single-pole for single line-to-ground faults) and selective-pole switching. In the latter case, the transmission system is balanced during the period between fault clearing and line reclosing using compensating capacitors. Moreover, an adaptive reclosing technique is used for reclosing the tripped phases. The effect of employing the adaptive short-time compensation and reclosing technique on the expected maximum torsional torques as well as their variances has been investigated. A risk index which reflects the likelihood that the torque induced in a turbine-generator shaft exceeds its design value is also presented