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EPQU Magazine - Vol 2 Issue 2

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The Importance of Power Quality on Appliance Safety

Submitted by Isabelle Heriakian on Sat, 2006-12-09 01:00.

Philip F. Keebler, Kermit O. Phipps, Bill Howe

This papers in on the union between appliance controls and safety-related systems.


What is reliability?

Submitted by Isabelle Heriakian on Fri, 2006-12-08 01:00.

Reliability and Reliability Indices in the Viewpoint of the Network Operator and in the Viewpoint of the Customer        

Math H.J. Bollen, Mats Häger

STRI AB in Ludvika, Sweden           

Summary: This paper explains the different definitions of the term „interruption” as used by the network operator and individual customers, especially industrial customers. The different viewpoints are strongly related to the different demands placed on these two stakeholders. Reliability indices are presented as a way to enable communication. A compatibility gap is identified due to the different demands on network operator and customer. Appropriate responsibility sharing is needed to remove this gap.   

Low Voltage, but High Tension

Submitted by Isabelle Heriakian on Thu, 2006-12-07 01:00.

Femmy M. COMBRINK, Peter T.M. VAESSEN

KEMA, The Netherlands   

Summary: A shift is taking place within low voltage (LV) networks. Electricity demand is growing, the amount of distributed generation is increasing, and more and more distributed generation (DG) techniques are being developed to fulfil the needs of end users. These developments are having a large impact on low voltage networks. The function of these networks changes and the installation of large scale DG present the operators of low voltage networks with additional challenges, mainly technical, but also concerning the control of the network. This paper describes the impact of installing large scale DG on low voltage grid operators.

Some Idea on Energy Comsumption of Non-Linear Consumers

Submitted by Isabelle Heriakian on Wed, 2006-12-06 01:00.

Miklós Horváth, József Borka

Hungarian Academy Sciences, Hungary        

Summary: The determination of energy consumption required by non-linear consumer results in numerous dilemmas. According to some conceptions the energy consumed by non-linear consumers ought to be calculated or measured by taking the favoured harmonic components only into considerations instead of the all harmonic content of voltage and current supplying the non-linear consumer. The paper shows how to change the value of energy calculated by the full harmonic content of the measured voltage and current, respectively, e.g. by the fundamental harmonic of voltage in the case of the most typical consumer, the two-wave connection rectifier with buffer condenser as non-linear load. It is especially interesting for practical arrangements where non-linear consumers resulting in similar network pollution and rectifier loads are connected parallel to the same line.

Risk Evaluation of Results when Utilizing Software Simulations to Identify a Harmonic Offender in a Power System

Submitted by Isabelle Heriakian on Tue, 2006-12-05 01:00.

Willem Stemmet, Gary Atkinson-Hope

Cape Peninsula University of Technology, South Africa

Summary: When evaluating harmonic software packages, some of the default element models (e.g., six-pulse drive) and analysis methodologies used are different and cause risk to results. Another problem is when multiple drives are present, the injections from drives add vectorialy at the PCC. Thus, a further risk to results arises as the vector addition is highly dependant on the methodology (e.g., referencing of drives) used to obtain the actual value for the phase angles for the injections. Also drives are often harmonic offenders, causing transgression of IEEE 519 limits. The focus of this paper is to develop a method to identify a harmonic offender and do risk evaluation of results. Indices are developed for identifying a harmonic offender (HOFFENDER) and to determine errors to results DHOFFENDER,  respectively. Risk flowcharts are also developed as a tool to assist and simplify the comparison of default element models and methodologies used by the three packages evaluated in this paper. The indices and flowcharts comprise a new method to determine if a drive is a harmonic offender or not and to do risk to results evaluation. Three case studies within two scenarios are conducted to demonstrate the effectiveness of this method.

Mutual Interaction between a Harmonic Load and the Feeding Transformer

Submitted by Isabelle Heriakian on Mon, 2006-12-04 01:00.

Stefan Fassbinder

Deutsches Kupferinstitut, Germany

Summary : Transformers in public electricity grids do more than just provide galvanic isolation and alter the ratio of voltage by current for a given amplitude of apparent power. They also introduce a substantial portion of inductive reactance into the system, which is important for both the feeding grid’s and the fed mains’ behaviour in cases of short circuits and earth faults. They are also capable of creating a system with a star point out of a system – of the same or a different voltage level – which does not provide a star point connection.     

Now the influences of all of these properties upon the system can today be calculated reasonably well by means of adequate programmes, but the calculations always relate to the rated mains frequency of 50 Hz or 60 Hz. If the transformer is feeding substantial shares of non-linear loads, then the total load current includes quite a number of frequencies rather than just one, and each of these is influenced by the transformer in a different manner. Vice versa, load currents of different frequencies take different effects upon a transformer. How can these influences be quantified, and how do they have to be taken into account when designing an electricity supply system today? This paper wants to offer a practical approach for those cases where theory gets stuck.

Although the mutual effects are basically quite evident, they are a bit difficult to understand and to explain consecutively, because they occur simultaneously and are interdependent. It shall be tried below to explain separately what actually happens jointly.

Interharmonics Generated by Induction Machines

Submitted by Isabelle Heriakian on Sun, 2006-12-03 01:00.

Jan Rusek

AGH University of Science and Technology, Poland  

Summary: The paper presents results of calculations of interharmonics generated by a squirrel cage induction machine, in both the healthy and faulty operating conditions. Two case studies refer to broken bars and clutch wobbling. The analyses were accomplished by a dedicated digital system for offline diagnosis of induction machines.

Spectral Analysis of Signals of Commutator DC Motor

Submitted by Isabelle Heriakian on Sat, 2006-12-02 01:00.

Zygfryd Głowacz, Antoni Zdrojewski             

Summary: Measurement investigations have been carried out for commutator dc motor with internal asymmetries. Construction of considered motor enables to realize the breaking of one rotor coil and shorting of two groups of rotor coils. Each group contains three rotor coils. The basis of study were transients: current and voltage of field winding, current and voltage of armature winding and velocity of the rotor.  In paper are presented selected measurement results and corresponding results of spectral analysis.   


Modern 3D Modelling, Visualization and Animation at Power Electrical Engineering Study Programme

Submitted by Isabelle Heriakian on Fri, 2006-12-01 01:00.

Hana KUCHYŇKOVÁ, Vítězslav HÁJEK

Brno University of Technology, Czech Republic          

Summary: There is a tendency to enable a higher education for much more students in comparison with recent times. This, of course, concerns also technical universities. This aim calls for principally new modern methods of education, including creativity, invention and demonstration methods. One of the possibilities is to provide lectures with presentation of up to date computer aided design methods and their use in 3D technical documents preparation. The main goal for implementation of both new CAD packages and contemporary forms of technical documentation is to contribute to an independent creative ability of bachelor students.  This paper has been presented at the conference SME 2006, Cracow, Poland.