Anastasia S. Safigianni

Optimum voltage regulator placement in a radial power distribution network

A computer algorithm for optimal voltage control with voltage regulators, suitable for large radial distribution networks is given in this paper. An objective function concerning the total cost of the voltage regulators (investment and maintenance cost) as well as the cost of losses of the examined networks is developed and constitutes the base of the algorithm. This algorithm makes the initial selection, installation and tap setting of the voltage regulators, which provide a smooth voltage profile along the network, utilizing former algorithms suitably modified and optimized. Then it attempts to minimize the number of the initially selected voltage regulators as much as possible, by moving them in such a way as to control the network voltage at the minimum possible cost (maximization of the objective function). The algorithm is fast, efficient and reliable as its application to practical distribution networks shows.

Measurements of electric and magnetic fields due to the operation of indoor power distribution substations

In this paper, the electric and magnetic fields with a frequency of 50 Hz, caused by the operation of indoor power distribution substations of 20/0.4 kV, are examined. First, the results of previous relevant research studies as well as the reference levels for safe general public and occupational exposure given in the guidelines of the International Commission on Non-Ionizing Radiation Protection are presented. Next, basic data for standardized indoor power distribution substations used in Greece, where the measurements have been carried out as well as a brief description of the field measurement instruments used are given. The results of the electric- and magnetic-field measurements in indoor power distribution substations of all the standardized nominal power ratings in the town of Xanthi, Greece, accompanied by relevant tables and diagrams follow. After the evaluation of these results, according to international guidelines, final conclusions are set out concerning safe public and occupational exposure to the above-mentioned fields.

Electric- and Magnetic-Field Measurements in an Outdoor Electric Power Substation

This paper investigates the electric and magnetic fields values in the area of an outdoor electric power substation 2 times 50 MVA, 150/20 kV, in Xanthi, Greece. Results of previous relevant measurements and calculations, as well as the reference levels in force for safe general public and occupational exposure, are presented first. Basic data for the examined substation along with a brief description of the field measurement instruments used follow. The main results of the field measurements in the area of the aforementioned substation are presented in relevant tables and diagrams. Final conclusions, concerning safe public and occupational exposure to these fields, according to the international guidelines, are set out.

A Communication-Assisted Overcurrent Protection Scheme for Radial Distribution Systems With Distributed Generation

Conventional overcurrent protection schemes for radial distribution systems usually attempt to coordinate a recloser at the beginning of the feeder with the fuses on the laterals. The integration of distributed generation in distribution systems leads to problems related to protection coordination that are difficult to be solved by applying conventional protection techniques. This paper proposes an efficient communication-based protection scheme that implements common directional overcurrent relays instead of reclosers at the line, assisted by intertripping and blocking transfer functions. The proposed protection strategy guarantees selectivity regardless of whether the generating units are connected to the network or not, and can be designed retaining either the fuse-blowing or fuse-saving philosophy. Meaningful conclusions are derived from the application of the scheme on a test distribution system.

A Systems Approach to Corporate Sustainability in Energy Management of Industrial Units

This paper presents a ldquoproof of conceptrdquo system methodology for the energy management of industrial units examining them as socio-technical systems. The cybernetic viable system model (VSM) of Beer is used to consider an industrial unit as a viable organization and through this consideration to diagnose the technical and managerial gaps identifying the Best Interventions Plan according to principles of sustainability. Based on a case study concerning a Fertilizers Production Plant, a framework is developed that could be extensively used for energy management of industrial units. The systems approach of this framework emerges as a unique available tool to implement the principles of sustainability in industrial energy management.

Optimum long-term planning of a radial primary distribution network: Part I: Data description and first proposed network form

With this second part the paper dealing with the optimum long-term planning of a radial primary power distribution network is completed. In this part an algorithm for this planning is developed, taking into account the locations and the time variation of tJke load served by the examined network, technoeconomical constraints and functions given in Part I of this paper and previous papers of the authors. This algorithm finally proposes a network form selecting the proper conductors for the network segments and concrete years with the kinds of specific improvements to which this form must be subject inside the specific plan period in order to satisfy the continuous growing load in the technoeconomically best way.

Economically justified modification of a radial network to an optimal form

Abstract This paper presents a Turbo-Pascal program, which is the implementation of an algorithm for the optimization of an operating radical primary distribution network. Based on an optimum network form the program suggests conductor changes so as the annual profit from losses saving would offset the cost of capital for these changes and also technical constraints would be satisfied. With the use of pointers, tree data structures and recursive procedures, the computation process is dynamic and the problem solution is fast and complete.

Long-term optimization of radial primary distribution networks by conductor replacements

A method dealing with the technoeconomical long-term optimization of currently operating radial primary power distribution networks is developed in this paper. This method, taking into account the realistic locations and growth of the load served by the examined network and specific technoeconomical constraints, results in the proposal of conductor replacements which must be realized in the network segments at specified years of the plan period. This is in order to optimize the network technically as much as possible, defraying the minimum cost.

Economical optimization of a radial power network based on voltage drop criterion

This paper presents a Turbo Pascal program, which optimizes an operating radial primary distribution power network. The program suggests changes of conductor sizes so as to have an acceptable voltage profile across the entire network with the minimum cost. By using pointers and tree data structures the computation procedure is dynamic and the problem solution fast and complete.

Electric and magnetic field measurements in a high voltage center.

This paper investigates the electric and magnetic fields inside a high voltage center in Philippi, Greece, constituted both of 400/150 kV and 150/20 kV substation areas. Results of previous field measurements and calculations in substations are presented first. The basic data distinguishing the examined center from previously examined substations follow. The main results of the field measurements in the areas of the above mentioned center are presented in relevant diagrams. Conclusions arising from the comparison of the measured field values with relevant reference levels in force for safe general public and occupational exposure as well as with the results of previous research are finally given.