New Methods for Evaluating. Distribution Automation and Control. (DAC) Systems Benefits. Dale W. Ross, James Patton, Arthur I. Cohen, and. Marlyn Carson.
June
1981, p. 2978
New Methods for Evaluating Distribution Automation and Control (DAC) Systems Benefits
Dale W. Ross, James Patton, Arthur I. Cohen, and Marlyn Carson Systems Control, Inc., 1801 Page Mill Road, Palo Alto, California 94304
This paper summarizes research performed over a twenty-month period to develop new approaches to the planning of radial primary distribution systems. In particular, the research has ad¬ dressed two problems areas: . The development of optimization models for arranging or rearranging the radial structure of a system of feeders.for planning the normal operating configuration of the system. . The development of optimization models for reconfiguration (made possible by manual or automatic switching) of a radial system of feeders during either emergencies or planned outages. A model (DISOPT) was developed to accomplish a variety of distribution planning functions, including: . To transfer electric load from one feeder to another or otherwise redistribute load as it changes in magnitude and geographic distribution over a multi-year planning horizon. . To lower losses in radial distribution circuits through better feeder configuration. . To redesign the arrangement of radial feeder systems in conjunction with the upgrading of the distribution systems.as when converting to higher primary voltages. Similarly, a model (SWITCH) was developed to optimize the reconfiguration of radial feeder systems during emergency or planned outages. The SWITCH model can be used by electric utilities for a variety of planning and operating problems including : . Performing cost/benefit studies of proposed schemes for sectionalizing and reconfiguration of radial distribution systems. . Developing operating plans for the use of switches to re¬ configure feeders during planned outages (such as for maintenance or construction). . Performing comparative evaluations of the reliability of service provided in different portions of a utility's service area, to different classes of customers. . Planning remote control systems and other future distribution automation functions. The capabilities of the DISOPT and SWITCH models that have been developed were demonstrated in a variety of case studies. Some of the case study results points very positively to the usefulness of the DISOPT and SWITCH models: . One DISOPT case study based on an actual distribution system indicated it was possible to reduce distribution losses by 20% through rearrangement of the normal configuration of the radial .
system.
Several SWITCH
case
studies indicated that automatic
switching has the potential to reduce customer-hours of in¬ terruption by 20% to 90%, depending on the nature of the initiating fault. . The computational efficiency of the models is quite good. A description of evaluation needs for DAC application is presented in the paper along with general descriptions of the computer models. The results of the case studies are also presented. June 1981, p. 2987
Effects of Contacts in High
Voltage Injuries
A. Sanees, Jr., Senior Member, IEEE Medical College of Wis. & Wood VAC, 8700 West Wisconsin Avenue, Milwaukee, Wisconsin 53226
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J. B. Myklebust, Member, IEEE Neuroscience Research Laboratory, Veterans Admin. Medical Center, Wood, Wisconsin 53193 J. F. Szablya, Fellow, IEEE Washington State University, Pullman, Washington 99164 T. J. Swiontek Neuroscience Research Laboratory, Veterans Admin. Medical Center, Wood, Wisconsin 53193 S. J. Larson Medical College of Wis. & Wood VAC, 8700 West Wisconsin Avenue, Milwaukee, Wisconsin, 53226 M. Chilbert Biomédical Engineering, Marquette University, Milwaukee, Wisconsin 53233 T. Prieto Biomédical Engineering, Marquette University, Milwaukee, Wisconsin 53233 J. F. Cusick Medical College of Wis. & Wood VAC, 8700 West Wisconsin Avenue, Milwaukee, Wisconsin 53226 A previous study conducted in the hog demonstrated that currents from 4 to 70 amperes RMS and impedances from 130 to 477 ohms were measured with application of potentials from 2,100 to 14,400 volts. This study was conducted to extend the previous results and to investigate the results of electrode dimensions upon the amount of current flowing in the living subject. Twenty sedated hogs were used for this study. Two sets of experiments were conducted using single-phase 60 Hz potentials derived from a transformer variable from 10 to 1,000 volts. In the first set of studies the potentials were applied between a 40 x 60 cm steel plate placed on the hindlimb as one electrode. Contact on the opposite hindlimb of the hog and on the forelimb of the hog was made with a #2 ACSR wire. Wire-to-wire studies were done with a #4 copper wire wrapped around one hindlimb and contact made with a #2 ACSR wire on either the opposite hindlimb or the forelimb of the animal. In all cases the wire was brought into contact with the animal after the voltage was established. In the second set of studies, a 40 x 60 cm plate was placed on the hindquarter of the hog and disk electrodes with circumferences similar to the disk electrodes and annulus electrodes which had an outer diameter of 5 cm and inner diameter from 2 to 4 cm were used. These electrodes were brought into contact with the skin after the voltage was turned on. The pressure between the skin surface and the electrode was maintained constant. In another set of experiments, the saline tank was used to compare the electrode interface characteristics and to verify theoretical calculations. For all studies a one ohm resistor in series with the ground lead was used for current measurement. Current and voltage waveforms were measured with the Honeywell visicorder, Model 1858. All voltages and currents are RMS values. Results For the 10 to 1,000 volt studies, approximately six seconds was required to reach the maximum value of one milliamp with ten volts applied. Similar findings were observed up to 80 volts. Blisters occurred between 50 and 80 volts within 20 to 30 seconds. Second degree burns occurred at approximately 200 volts. The current began to decrease in each instance between 100 and 200 volts and increased linearly at potentials above this value. At voltages above 200 and below 100 volts, the currents were proportional to the voltages applied. The wire-to-wire contact studies demonstrated a 50 to 100% greater impedance than those obtained when the large plate was used on the hindlimb. Nonlinearities were observed in the current-versus-time and current-versus-voltage. Current-versus-
61
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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