Turbine-generator Shaft Torsional Torques Research Articles

Development of a Reclosing Scheme for Reduction of Turbine Generator Shaft Torsional Torques: A Decision Method to Achieve Optimal Reactor Capacity

It is well known that line switching operations like reclosing are able to cause transient power oscillations which can stress or damage turbine generators. This paper presents a reclosing scheme to reduce the shaft torsional torques of turbine generators by inserting an additional reactor. A novel method to determine optimal reactor capacity to minimize the torsional torque generated in a turbine generator is also proposed. In this paper, the turbine generator shaft is represented by a multi- mass model to measure torsional torques generated in the shaft between the turbine and the generator. Transmission systems based on actual data from Korea are modeled to verify the proposed scheme using ElectroMagnetic Transient Program (EMTP) software. The simulation results clearly show the effectiveness of the proposed scheme and torsional torque can be minimized by applying the proposed scheme.

Stochastic evaluation of turbine-generator shaft torsional torques in a HVAC/DC power system

This paper presents a Monte Carlo based approach to evaluate the maximum torsional torques induced in turbine-generator shafts during faults on a HVAC/DC power system. In this context, investigations have been conducted on a large turbine-generator model taking into consideration the uncertainty of various factors associated with the practical operation of a power system. The results of these investigations are presented in the form of probability distributions of the maximum torsional torques induced in the turbine-generator shaft sections. A risk index that reflects the likelihood that the torque induced in a turbine-generator shaft exceeds its design value is also presented. Moreover, the paper presents a method for calculating the expected life expenditure ratio and the expected lifetime of turbine-generator shafts.

Impact of six phase transmission line faults on turbine-generator shaft torsional torques

This paper explores the impact of six-phase transmission line faults and their subsequent fault clearing and reclosing on the torsional torques induced in turbine-generator shafts. In this context, investigations have been conducted on a large turbine-generator unit connected to a sample power system. The paper presents also a comparison between the torsional stresses induced in the turbine-generator shafts during these events with their corresponding disturbances of a three-phase transmission system. The results of these investigations are presented in the form of typical time responses as well as parametric studies. The EMTP is used for the simulation studies. The studies conclude that six-phase transmission line faults generally induce torsional torques in the turbine-generator shaft whose magnitudes are relatively higher than those induced due to transmission line faults in a three-phase system. This conclusion is true for both sustained faults and faults followed by clearing and high-speed reclosing operations.

A New Single-Pole Switching Scheme for Improving Power System Stability

This paper presents a new single-pole switching scheme for improving power system stability and reducing turbine-generator shaft torsional torques. The fundamental concept of the proposed technique is to interrupt single line-to-ground faults on double-circuit transmission lines using single-pole switching. The transmission system is then balanced using a Thyristor Controlled Series Capacitor (TCSC) in the interrupted phase. Adaptive reclosing is then applied to reclose the tripped phase and the compensating capacitor is switched off. The validity and effectiveness of the proposed technique are demonstrated through time-domain simulation studies on a test system using the Electromagnetic Transient and Direct Current Program (EMTDC) program.

An adaptive short-time compensation scheme for improving power system stability and reducing turbine-generator shaft torsional torques

This paper presents an adaptive short-time compensation and reclosing technique for improving power system stability and reducing turbine-generator shaft torsional torques. The fundamental concept of the proposed technique is to interrupt unsymmetrical faults on "double-circuit" transmission lines using selective-pole switching. The transmission system is then balanced by switching on compensating capacitors in the interrupted phases. Adaptive reclosing is then applied to reclose the tripped phases and the compensating capacitors are switched off. The validity and effectiveness of the proposed technique are demonstrated through time-domain simulation studies on a test system using the EMTDC program.

Effect of adaptive short time compensation on the stochastic behavior 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.

A Monte Carlo simulation approach to the evaluation of maximum turbine-generator shaft torsional torques during faulty synchronization

In this paper a Monte Carlo based approach to the evaluation of the maximum electromagnetic and torsional torques induced in turbine-generator shafts during faulty synchronization is presented. 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 a more precise synchronization device on the expected maximum turbine-generator torques as well as the probability density function of such torques have also been investigated. The results of these investigations are presented in the form of probability distributions of the maximum torsional torques induced in the turbine-generator shaft sections.

Effect of adaptive single-pole reclosing on the stochastic behavior of 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.

Effect of HVDC converter station faults on turbine-generator shaft torsional torques

This paper explores the impact of HVDC converter station faults on the torsional torques induced in turbine-generator shafts. In this context, investigations have been conducted on a large turbine-generator unit connected to an HVDC system. Faults considered are firethrough, misfire and a short-circuit across a nonconducting valve. The effect of the fault incidence time on the maximum turbine-generator torsional torques is also investigated. The results of these investigations are presented in the form of typical time responses as well as parametric studies.

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.

Stochastic evaluation of turbine-generator shaft torsional torques during faulty synchronisation

A probabilistic approach to the evaluation of the maximum torsional torques induced in turbine-generator shafts during faulty synchronisation is presented. This approach is based on utilisation of the conditional probability theorem to assess these torques. 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 reclosing on turbine-generator shaft torsional torques

This paper presents the adaptive reclosing technique as a new concept to reduce the high torsional torques to which turbine-generator shafts might be subjected during high-speed reclosing of multi-phase power system faults. In this context, investigations have been conducted on a large turbine-generator model for various multi-phase faults. In this paper, the principle of such an adaptive reclosing technique is explained and its effectiveness is demonstrated in the case of three-phase faults. The paper presents also the idea of applying the principle of adaptive reclosing to single-pole reclosing.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of sequential reclosure of multi-phase system faults on turbine-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 controlling the sequential interruption of a system fault on 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.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Effect of field discharge resistors on turbine-generator shaft torsional 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. >