The paper considers the justification for the application of light-emitting diode (LED) technology to urban lighting. The results suggest that LEDs are convenient for architectural lighting and deserve to be considered for use in ambient lighting. The recently developed Commission Internationale de l'Eclairage (CIE) mesopic system enabled the inclusion of mesopic effects into a comprehensive technoeconomic analysis, which dealt with efficiency, maintenance and financial aspects of the use of LEDs in street and roadway lighting. It is concluded that the average energy savings when using LED instead of high-pressure sodium (HPS) luminaires amount to 19-26% for single-sided, staggered and opposite layouts, although they are frequently negligible if mesopic effects are not included. The total costs of the LED lighting solutions, even including mesopic effects, are 1.36 to 6.44 times higher than those of the comparable HPS lighting solutions. Therefore, LEDs are questionable for street and roadway lighting.

This paper presents experimentally obtained luminous flux to input power characteristics of high-pressure sodium and LED luminaires used in road lighting, confirming that when applying dimming scenarios more percentage energy savings can be achieved by an LED than by a corresponding high-pressure sodium lighting installation. However, both workshop and field experiments showed that the tested LED drivers (of either standard or improved dimming characteristics) have the disadvantage of poor power factors (down to 0.67) at low light levels achieved by dimming. In addition, an increased presence of current harmonics and high values of the current total harmonic distortion were noticed at low light levels, representing another serious disadvantage of LED technology regarding power quality. The relevant electrical characteristics of commonly used LED drivers were analysed in detail and the reasons for the poor power quality when dimming LED luminaires were recognised. A new generation of LED drivers with a considerably narrower range of input (AC) voltage will allow acceptable power factors and limited emissions of current harmonics to be achieved in practically all lighting regimes.

The paper presents a comprehensive analysis dealing with the behaviour and economics of electronic compact uorescent lamps. The economic analysis, based on the results of the test concerning the lifetime and the lamp lumen maintenance factor of electronic compact uorescent lamps, and conducted using the costdiscount method, showed an obvious advantage for lamps of this type compared with incandescent ones. The strategic importance of the mass use of electronic compact uorescent 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. List of symbolsCFL compact uorescent lamp GLS general lighting service LLMF lamp lumen maintenance factor lm x LLMF lowest maintained luminous ux of the lamp (lm) T y lamp operation per year (h) T compact uorescent lamp life (years) C IL total cost of operation of an incandescent lamp ($) C CFL total cost of operation of a compact uorescent lamp ($) R retail cost of a lamp ($) i discount rate (%)

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 remarkable conclusions concerning the problem of harmonics are drawn.

Numerous measurements have shown that the standard R classes do not represent adequately many road surfaces used nowadays. Therefore, the construction of portable reflectometers intended for on-site measurements of road surface reflection properties has been given particular attention during the last decade. This paper presents a new procedure for the improvement of the accuracy of such a portable reflectometer. Optimally extrapolating the values of the 20 luminance coefficients (q), each measured by the portable reflectometer for a set of angles of observation (α = 5°–80°), the 20 q-values referring to α = 1° are calculated. This enables their comparison with the corresponding q elements from each of the 447 reduced q-tables derived from the available r-table database, obtained by using a precise laboratory reflectometer on a wide variety of road samples. Selecting the closest reduced q-table, the corresponding r-table and the actual average luminance coefficient can be determined. In order to validate the proposed procedure, which can also be applied to other similar portable reflectometers, measurements of the luminance and overall and longitudinal luminance uniformities were carried out on eleven road-lighting installations. They showed that the results obtained by this procedure deviate only slightly from those obtained using r-tables determined by the laboratory reflectometer.