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 sequential reclosure of multi-phase system faults onturbine-generator shaft torsional torques

The authors present a method of reducing the high torsional torques induced in turbine-generator shafts during high-speed reclosure of multiphase system faults. The method is based on the sequential reclosing of the faulted circuit. In this context, investigations have been conducted on two turbine-generator units of different designs for various multiphase system faults. The results of both the three-phase-to-ground and double-line-to-ground faults are reported, and the effectiveness of the method is illustrated through parametric studies and simulation results. The effects of the reclosing time and the fault incidence instant on the effectiveness of the method have also been investigated     

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.     

Model-Theoretic Properties of ω-Automatic Structures

We investigate structural properties of ω-automatic presentations of infinite structures in order to sharpen our methods to determine whether a given structure is ω-automatic. We apply these methods to show that several classes of structures such as pairing functions and infinite integral domains do not have an ω-automatic model.     

Effect of field discharge resistors on turbine-generator shafttorsional torques

The possibility of reducing the torsional torques of turbine-generator shafts during disturbances by interrupting the generator excitation and switching in a field discharge resistor during the fault duration is discussed. The results of these investigations show that the use of such field discharge resistors reduces the turbine-generator torsional torques after the fault clearance. These results have been obtained through extensive parametric studies and are supported by simulation results     

Effect of controlling the sequential interruption of a system faulton turbine-generator shaft torsional torques

A new method is presented to reduce the high torsional torques induced in turbine-generator shafts during the clearing of multiphase faults. This method is based on controlling the sequential interruption of such faults. In this context, investigations have been conducted on two turbine-generator units of different designs for both three-phase and double line-to-ground faults. The effectiveness of the proposed method is illustrated through parametric studies and simulation results. The effects of the fault clearing time, the strength of the system to which the unit is connected, and the fault incidence instant on the effectiveness of the method have also been investigated     

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