Stability Limit Of System Research Articles

An Evaluation of Power-Factor Correction on a System Basis [includes discussion

IN planning future load capabilities for a system having integrated transmission and distribution facilities, it is important that the economic limits be known for supplying the system's reactive loads with shunt capacitors. In the majority of the many cases1,2 dealing with the economics of capacitor application, treatment is made of only the resulting benefits to a particular portion of the system, or to a particular item of system costs, such as the savings in losses. A true evaluation of load power factor correction should, however, include all the simultaneously resulting benefits from the location of the capacitor back to the alternate source of reactive supply. The over-all benefits should be appraised on the basis of: 1. Costs for facilities to generate with synchronous equipment, transmit, and distribute reactive loads. 2. Costs for compensation of voltage regulation caused by the transmission and distribution of reactive loads. 3. Costs for losses. 4. Costs incurred because of changes in system stability limits.

A Simplified Approach to Steady-State Stability Limits [includes discussion

A numerical study has been made which shows the effect of shunt loads on the steady-state stability limit of a power system. In particular, the effect of the load characteristic, i.e. constant impedance, or constant current, or constant power, was considered. In general, the study shows shunt loads to have a stabilizing effect on the system except when the load is heavy, nearly constant power in nature, close to a machine which supplies a minor part of the loads requirement, and poorly connected to the rest of the system. On the basis of this study and a-c network analyzer tests, a simplified method for determining the stability limit is developed and presented herein. Equations for the stability limit are also presented.

Location of Series Capacitors in High-Voltage Transmission Systems [includes discussion

Over-all system economy can be improved by means used specifically to increase the power limits of high-voltage, large-conductored transmission lines.1-24 Important methods for increasing the stability limits of high-voltage transmission systems are: 1. Intermediate switching stations, with and without series capacitor compensation. 2. Intermediate systems. 3. Automatic circuit reclosing. 4. Switched shunt capacitors and reactors. 5. Generator excitation systems. This paper reviews and compares four possible methods of applying series capacitors, together with intermediate switching stations for improving the transient stability limit of high-voltage systems. The function of intermediate switching stations to improve the stability limits of transmission lines is primarily that of removing transmission line faults by disconnecting a smaller line section with a correspondingly smaller shock than if intermediate switching stations were not used. Detailed studies of intermediate switching stations have been previously reported24 which indicate that they can be economical for lines as short as 50 miles. Series capacitors reduce the over-all line reactance, and hence allow a larger stable transfer of power. Series capacitors can also be applied to obtain better load division21,22 on parallel lines having different conductor resistances and/- or different lengths, although series capacitors applied for this purpose show only marginal economic benefits. In general, series capacitors appear to be economical for increasing the stability limit of lines about 200 miles or longer. There has been, however, some divergence of opinion as to the most economical location for the series capacitors in the transmission system.

A computer for use in power-system transient stability studies

The transient stability limits of power systems are determined by assuming conditions to be constant over short intervals of time and using the results obtained at the end of one interval to vary the conditions at the beginning of the next interval. The analysis is tedious and it is easy to make numerical errors. If a large number of machines is involved, it is essential to use an a.c. network analyser for determining the values of power to be used for the different time intervals, but there is no reduction in the computation labour, and in practice the greater part of the time taken for a study is devoted to the latter. To reduce the computation time and the possibility of numerical errors, the ?step? evaluations can be carried out semi-automatically by using the computer described. Furthermore, by reducing the time interval, greater accuracy can be obtained without an increase in overall time as compared with normal procedure.

Static Stability Limits of Ultra High Voltage Transmission Systems

Static Stability Limits of Ultra High Voltage Transmission Systems

A graphical solution of steady state stability

The steady state stability limit of a power system, and adjusted synchronous reactance, are considered in this paper. A graphical solution of the problems of the determination of the steady state power limits is described, based directly upon the use of the general circuit constants of the transmission line.

A Graphical Solution of Steady State Stability

The steady state stability limit of a power system, and adjusted synchronous reactance, are considered in this paper. A graphical solution of the problems of the determination of the steady state power limits is described, based directly upon the use of the general circuit constants of the transmission line.

Experimental Analysis of Stability and Power Limitations

A method of determining the power and voltage stability limit of a transmission system taking into account the characteristics of the synchronous condenser and load in conjunction with the characteristics of the line is described. The power limit of a straight 500-mile transmission line is calculated by this method. The power limit is also calculated for the same line with a synchronous condenser at the mid-point which divides the line into two sections. The addition of the synchronous condenser at the mid-point increased the power limit 42 per cent. Tests were made on a 625 kv-a. transmission system operated at 2300 volts to determine experimentally the power and voltage stability limit of a transmission line with a synchronous condenser at the mid-point. The tests check closely with the calculated values. Tests on hunting caused by prime mover pulsations, line characteristics and voltage regulator adjustment were made. It was found that the damper windings on synchronous condensers do not have much effect in reducing hunting, particularly at resonant points. There was practically no difference between the standard high-resistance windings used for starting purposes and low resistance copper damper windings. On a high-resistance and low-reactance transmission line hunting was found to occur at high condenser field excitations. The addition of reactance stabilized the system. On high-voltage transmission lines the reactance is high as compared to resistance and no difficulty from hunting due to line characteristics is to be expected.