Frangiskos V. Topalis

Efficiency of energy saving lamps and harmonic distortion in distribution systems

The aim of this paper is the investigation of the electric and photometric characteristics of energy efficient lamps. These lamps consume less active power and produce higher luminous power as compared with the traditional incandescent ones. However, a lot of those lamps operate at relatively low power factor, demanding additional reactive power factor from the utility power system. On the other hand those lamps introduce significant harmonic distortion to the distribution system. In this paper, measurements of the above characteristics on many types of energy saving lamps are presented. >

Influence of large-scale installation of energy saving lamps on the line Voltage distortion of a weak network supplied by photovoltaic station

The aim of this research is to calculate and analyze the harmonic distortion extent caused in weak low-voltage networks due to a possible large-scale installation of the widely spread compact fluorescent lamps (CFLs). The research uses data from laboratory measurements of the produced harmonic currents by CFLs, as well as field measurements of the harmonic content and other characteristic measurements of the electric network of a small Greek island, which is supplied by an autonomous photovoltaic (PV) station. The PV station is also a harmonic generator by itself. This fact combined with other highly nonlinear loads-such as CFLs-causes serious problems at the network power quality as undesirable harmonic components are induced. The whole network is simulated and three scenarios of CFL installation extent are considered, so that the harmonic flow analysis reveals the influence in the power quality. It is examined whether this weak low-voltage electric network is able to keep the total harmonic distortion factor at all nodes under 8%, as more and more CFLs are installed. The conclusions drawn from this analysis are important and must be taken into account in every electric network design.

Probability of backflashover in transmission lines due to lightning strokes using Monte-Carlo simulation

A method, which estimates the lightning performance of high voltage transmission lines based on the Monte-Carlo simulation technique, is described in this paper. The average number of faults which occur in a transmission line, dividing them in single-phase and three-phase faults, as well as the average grounding resistances of the transmission lines are calculated. The method is applied, on several operating Greek transmission lines, showing good correlation between predicted and field observation results. The proposed method can be used as a useful tool in the design of electric power systems, aiding in the right insulation dimensioning of a transmission line.

Arbitrary waveform generator for harmonic distortion tests on compact fluorescent lamps

Abstract This paper presents an experimental method to perform tests on compact fluorescent lamps operated with distorted voltage waveform conditions. The voltages used for the tests are obtained from an arbitrary waveform generator. It consists of a computer, a multifunction card and the software package. The characteristics of the voltage are entered from the computer that loads the required waveform into the card. The output of the card is driven to a voltage amplifier to supply the lamps. Samples of the voltage across the load and of the circulating current are recorded and transferred to the computer for harmonic analysis. The user supervises the tests through several virtual instruments that have been developed especially for this application. The system facilitates the performance evaluation of various appliances for distorted supply voltages. The cost of the system is very low compared with a conventional system consisting of an arbitrary waveform generator, a digital oscilloscope, a spectrum analyzer or/and a computer for harmonic analysis and a true rms multifunction meter. The experimental results show that the distribution of the harmonics of some lamp types does not alter linearly under distorted supply voltages.

Influence of ground and corona currents on dielectric behavior of small air gaps

This paper investigates the influence of grounding on the field distribution and on the dielectric behavior of small rod-plate and rod-rod air gaps. This effect can be attributed to the grounding of one electrode. In the different arrangements with one electrode grounded or with the electrodes symmetrically charged the experimental results of the corona and breakdown are recorded and compared to the simulation results of the field distribution. It is resulted that the grounding influences significantly the electric field distribution, the dc corona and the dc breakdown. The field is less inhomogeneous in grounded rod - plate air gaps and in rod-rod air gaps with symmetrically charged electrodes, and consequently the values of the corona onset and the breakdown voltage are higher. In longer air gaps the corona current influences the field distribution and consequently the dc breakdown. The effect of grounding on the breakdown is weakened when the dc polarity of the voltage is negative, otherwise it is enhanced. In air gaps with lengths > 3 cm (negative dc polarity) or >8 cm (positive dc polarity) it is overlapped by the effect of the corona current. Relations between the field strength, the corona current, the corona onset and the breakdown voltage arise. The principle of action-reaction is valid.

Harmonic distortion in electric power systems introduced by compact fluorescent lamps

The purpose of this paper is the investigation of the harmonic distortion introduced by the compact fluorescent lamps to the distribution systems. The results of some measurements on compact fluorescent lamps (CFL) and on self-ballasted fluorescent lamps (SBL) of various wattages are presented. Some of the most important electrical characteristics (voltage, current and power factor) were measured by a data acquisition system. The harmonic spectrum and the total harmonic distortion (THD) of the lamps were calculated using Fourier analysis of the recorded current waveforms. The measurements were performed with supply voltage other than the nominal one in order to determine the dependence of the THD variation upon the mains supply voltage. From these measurements, conclusions concerning the problem of harmonics are drawn.

Influence of compact fluorescent lamps on the power quality of weak low-voltage networks supplied by autonomous photovoltaic stations

The principal goal of this research is to determine the influence of compact fluorescent lamps (CFLs) harmonics on the voltage distortion of a weak electric network supplied by an autonomous photovoltaic (PV) station. The total harmonic distortion factor at all points of the electric network must be under 5%. The power electronics of a PV station and other highly non-linear loads such as CFLs induce undesirable harmonic components and cause serious problems at the network power quality. For that reason, a specific methodology is developed, which uses data from field measurements of the harmonic content and other characteristic measurements of the PV station supplied electric network of the island of Arki. Then, after simulating the whole network, a harmonic flow analysis takes place showing the extent that CFLs influence the power quality. The conclusions drawn from this analysis are important and must be taken into account in every electric network design.

Cooperative approaches for dymanic wireless charging of Electric Vehicles in a smart city

In this paper, a method of electric vehicles charging with the use of large truck/bus vehicles moving along national highways and provincial roads is proposed and described. The method relies on charging vehicles from trucks while moving either with plug in electric connection or by electromagnetic induction via loosely coupled coils. Open research challenges and several avenues or opportunities for future research on Electric Vehicles Charging are outlined. The proposed method overcomes the disadvantages of the so far known techniques. The advantages of this method compared to the so far proposed methods are a) economical, easy and safe procedure, b) increase of the energy transfer efficiency factor, c) minimization of the delay in vehicle movement during the charging procedure and d) reduction of the environmental contamination with CO2 or electromagnetic radiation.

Energy efficiency of distribution transformers in Europe

Losses in distribution transformers account for almost one third of overall transmission and distribution losses. Previous European Copper Institute studies indicated that improving energy efficiency of existing European stock of transformers by 40% would result in about 22 TWh energy savings equivalent to about 9 million tonne of CO2eq. SEEDT is one of the projects developed under Intelligent Energy - Europe programme which converts EU energy policy for todays energy challenges like energy efficiency. One the main goals is to update and scrutinize knowledge about energy efficiency in distribution transformers in Europe. This paper presents findings of analysis of existing situation.

Advantages and disadvantages of the use of compact fluorescent lamps with electronic control gear

The paper presents a comprehensive analysis dealing with the behaviour and economics of electronic compact fluorescent lamps. The economic analysis, based on the results of the test concerning the lifetime and the lamp lumen maintenance factor of electronic compact fluorescent lamps, and conducted using the cost-discount method, showed an obvious advantage for lamps of this type compared with incandescent ones. The strategic importance of the mass use of electronic compact fluorescent lamps, as well as serious power quality implications it can cause to the network, are explained in detail. Possible solutions of this problem are also presented.