General Electric Company, Schenectady, New York. Power system stabilizers have been applied to generator excitation systems to aid damping of power ...
time curve showed marked rise during the first second with a decrease thereafter during the period that arcing and tissue damage occurred. Saline tank studies showed that the resistance of the disk and eliptical electrodes were more nearly proportional to the distance around the periphery of the electrode than the area. Theoretical calculations confirm that a substantially greater amount of current flows at the edge of the electrode than at the center. The formula derived from our group, based on the experimental findings, reduces the equation to the conventional equation for the disk electrode. The electrode studies in the hog showed a rapid increase in current with voltage application followed by a decrease which was attendant with arcing and tissue damage. The amounts of current were proportional to the applied voltage. The time required for the increase in current following voltage application was inversely proportional to the applied voltage and proportional to the electrode size. Current-versus-voltage and current-versus-time plots for eliptical disk and annular electrodes were similar for electrodes with the same distance along the edge. Studies conducted with a thermographie scanning system showed that the temperature in the Saline tank and in the hog was greater in the region of the electrode edge than at the middle. These studies indicate that a non-linear phenomenon is observed below 1,000 volts due to cooking away of the fluids in the tissue and then arcing was attendant with an increased impedance. These results were not observed in studies at voltages of 2,000 volts and above. The higher potentials have substantially more energy capable of penetrating the skin, arcing over into muscle and deep tissue which circumvents the non-linear phenomenon. These studies demon¬ strate that the distance along the electrode edge is more critical to the passage of current than the area. June 1981, p. 2993
Selected Non-IEEE Bibliography on
Grounding
Krishna G. Komaragiri CAE Electronics Limited, Montreal, Canada Dinkar Mukhedkar, Senior Member IEEE Ecole Polytechnique, Montreal, Quebec
This bibliography lists papers on power system grounding from 1961 to 1979. The papers have been classified on a country wide basis. All the papers are written in the language of the respective country. No literature from North America is included. June 1981, p. 3002
A Reversible Smooth Current Source with Momentary Internal Response for Nondissipative Control of Multikilowatt de Machines Francise C. Schwarz, Senior Member IEEE and J. Ben Klaassens State University of Technology, Delft, The Netherlands A de machine drive is in the form of a reversible source of almost current is presented. The internal current source mechanism is suited for the submegawatt range and responds at most within 50 ptsec to externally applied commands. Static characteristics and the dynamic conditions during internal current reversal and the therefrom resulting effects of machine behavior are presented. The advantages of the system are the appreciable speed of response, the therefrom derived improvement of dynamic stability and the low cost of production.
ripple free
62
June 1981, p. 3008
Substation Interlocking and Sequence
Switching Using a Digital Computer A. Traca-de-Almeida, Member, IEEE
Dep. Engenharia Electrotechnica, Universidade de Coimbra, Portugal
Power systems on-line control is being studied and applied for its technical and economical advantages. This paper presents the work carried out with a substation model, interfaced with digital processors for data acquisition and control, to develop and test on-line strategies to control switching operations. A network representation model containing switch data is scanned to forecast the effects of any switch operation providing a comprehensive and flexible interlocking scheme. Extension of the concept to optimal sequence switching is also presented. June 1981, p. 3017
Applying Power System Stabilizers. Part I: General Concepts
E. V. Larsen and D. A. Swann General Electric Company, Schenectady, New York
Power system stabilizers have been applied to generator excitation systems to aid damping of power system electro¬ mechanical oscillations since the mid-1960's. The art and science of applying power system stabilizers has developed considerably over these past 10 to 15 years, and has involved the use of various tuning techniques and input signals as well as learning to deal with practical problems such as noise and interaction with turbine-generator shaft torsional modes of vibration. This three-part paper describes the results of considerable analytical and field test work leading to the state-of-the-art of applying power system stabilizers. Emphasis is placed on the power system performance obtainable with stabilizers utilizing each of the three input signals considered most feasible: shaft speed, ac bus frequency, and a combination of power and speed. Use of any of these input signals has a set of advantages and disadvantages, which are explored in some depth. The paper concludes with a proposed set of guidelines for tuning power system stabilizers. Part I: General Concepts The general concepts associated with applying power system stabilizers utilizing shaft speed, ac bus frequency, and electrical power inputs are developed in this first part of the three-part paper. This lays the foundation for discussing tuning concepts and practical aspects of stabilizer application in Parts II and III. The basic function of a power system stabilizer is to extend stability limits by modulating generator excitation to provide damping to the oscillations of synchronous machine rotors relative to one another. These oscillations of concern typically occur in the frequency range of approximately 0.2 to 2.5 Hz, and insufficient damping of these oscillations may limit the ability to transmit power. To provide damping, the stabilizer must produce a component of electrical torque on the rotor which is in phase with speed variations. The implementation details differ, depending upon the stabilizer input signal employed. However, for any input signal the transfer function of the stabilizer must compensate for the gain and phase characteristics of the excitation system, the generator, and the power system, which collectively determine the transfer function from the stabilizer output to the component of electrical torque which can be modulated via excitation control. This transfer function, denoted GEP(s) in this paper, is strongly influenced by voltage regulator gain, generator power level, and ac system
strength.
The characteristics of the "plant," GEP(s) through which the power system stabilizer must operate are such that the gain in¬ creases with generator loading and ac system strength. Also, the phase lag of the "plant" increases as the ac system becomes
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