Measuring Electric Parameters in Street Lighting Networks

PETER JANIGA, DIONÝZ GAŠPAROVSKÝ, FRANTIŠEK JANÍČEK, ANTON BELÁŇ, ŽANETA ELESCHOVÁ, DOMINIK VIGLAŠ

Department of Electrical Power Engineering Slovak University of Technology in Bratislava

Ilkovičova 3, 812 19 Bratislava SLOVAKIA

peter.janiga@stuba.sk, http://www.fei.stuba.sk Abstract: - Public lighting networks represent important electric consumption. These networks can be found in all cities in Slovakia and other countries. Operation Costs associated with the operation significantly influence the budgets of municipalities. Incorrect or suboptimal design increases the cost of public lighting operation. For this reason is the effort to assess public lighting network not only in terms of lighting but also in terms of energy. The aim of this paper is to show the results of measurements in public lighting networks of current status in terms of electrical characteristics. Based on the measurements is possible to create an image of the actual power proportions in public lighting networks and also about the problems that arise after incorrect design. The optimal solution to the energy aspects of public lighting networks requires an assessment of a several technical and electrical inputs. Key-Words: - public lighting networks, energetic aspects, power measuring, smart metering

1 Introduction Public lighting networks are major purchaser of electricity and this is significant factor of spending. Factories and scientist are constantly looking for ways to reduce costs. Recently investigated method is the use of renewable energy to supply public lighting networks. These sources provide us theoretically infinite amount of energy. In some cases, etc. solar energy or wind energy no need fuel, which further eliminates costs. Financial calculation showed that the use of these resources is not so convenient for the public lighting network. As a secondary effect was found method for solar panels and wind power can provide power supply for public lighting in off grid operation. The creation of the described solutions requires a comlex analysis of the electrical parameters of the networks of public lighting. It is consequence of mutual interference. On the one hand, power systems affect lights functionality and other lights affect network functionality. Incorrect network design can cause many problems, etc. a control units malfunctions, incorrect measurement, influence to luminous flux, lamp life reducing and others. Network Design in off grid operation can cause other specific problems. For example, power supply for discharge lamps. If such lamps supplied by inverters, they can produce problems related to deformed voltage. Off grid inverters typically

generate voltage, which contains fundamental harmonic and higher harmonics. This distorted voltage causes a more distorted current flow and strain of network elements such as capacitors or inductors.

Fig.1 Small wind power plant (300 Wp), photovoltaic panel (130 Wp) and LED luminarie 31 W [1]

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2 Measurement of electrical

parameters in networks of public

lighting Lamp is a major appliance in public lighting networks. If we are investigating the exact consumption in the network then, we can not only calculate the final consumption of installed power by multiplying the time of operation. For better understanding the particularity of public lighting networks were measured electrical parameters in switchboards and endpoints of line.

Fig. 2 Analyzer connected to switchboard Analyzed were networks in Slovak Republic. Analyzed networks have various Year of construction; some were also reconstructed or newly built. A totally was analyzed 130 public lighting networks. Tab. 1 The analyzed public lighting networks

Municipality Michalovce

Dunajská

Streda

Number of measured switchboards 82 43

Line Cable,

overhead lines Cable,

overhead lines In terms of distribution network impact to the public lighting network measurements were made at the time of the minimum and maximum load distribution networks. Consumption affects the size of the surrounding customers and distorted supply voltage.

3 Measured data The aim of the measurements was to determine the consumption of public lighting networks and analyze the effects to power consumption. From the measurements is possible to identify specifics of public lighting networks in terms of electrical parameters. Measured were voltages and currents values. Stored were effective values and transients. Values were analyzed at start, during, and after stabilization. Values were measured in the switchboard and in selected line endpoints. From waveforms can be determined voltage and current harmonic analysis at start and after stabilization.

Fig. 3 Examples of measured data: Voltage, current, active power, reactive power in Dunajska Streda, switchboard 40, branch 1

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4 Specifics of public lighting networks

in determining the energy

consumption In the public lighting networks is a major appliance lamp. Exact determination of network power consumption in time is nearly impossible. This is due to many influences and variable network characteristics. Lamps and network analysis identified the following impacts on immediate consumption: - Voltage drop, - The impact of electrical equipment of

switchboard, line, connectors, fuse and luminaries, - Power variability of lamp during stabilisation, - Passive consumption of the network, - Control, measurement and communication

equipment consumption, - Effect of harmonic voltages and currents -

distortion power, - Installed regulators, - Variable operating time during the year, - Reactive power, - Load assymetry, - Connected other devices (kiosk lighting, building

illumination, etc.) Voltage drop The wires design in public lighting networks requires check current capacity and voltage drops too. Especially if is use the lighting regulator. This could be the case reduced voltage by regulator and great voltage drops at the end of the line. Great voltage drops cause problem with stabile discharge in lamp. This problem occurs mainly when the lamps with magnetic ballasts. Electronic ballasts can solve problem with voltage drop. From measurements realized in Matúškovo can see that at the end of the line was voltage out off the boundaries of EN 50 160. Although at the beginning of the branch almost nominal voltage. This situation occurred when at the beginning of the line were almost nominal voltage. This network was just before reconstruction and almost half of the lights are broken. Some lamp were connected to another phase but it is expected that already during the construction of the network with a 250 W mercury lamps were low voltage in lighting network and lamps were switched more often due to unstable discharge. This could cause the state where the two phases are broken.

Fig. 4 Voltage at the beginning of line (green) and at the end of line (red). Measuring in Matuskovo Power variability of lamp during stabilisation Lamps used in street lighting used discharge lamps. For these sources are characterized progressive fixer parameters. Stabilize the discharge and the electrical parameters are no longer than 15 minutes.

Fig. 5 Variable current during stabilisation of lamp in public lighting network (inductive ballasts – upper, electronic ballasts – bottom) Control, measurement and communication

equipment consumption

The calculations consider only resistance lines. Reactance is ignored because it is several times smaller. By measuring in real networks with nine lamps confirmed little impact on the course of the

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current reactance. The following figure shows the harmonic content does not change with distance, but only due to distorted voltages, slight differences due to age lamps (lifetime lamps are changing the electrical parameters) and small variations of electrical parts (the same lighting parameters are slightly different). Passive consumption of the network

Consumption in network consists of the consumption of lamp and consumption of other equipment. Usually these elements are placed in the switchboard. Passive consumption and the consumption of auxiliary equipment can be divided into two groups: - Consumption depends on the installed power consumption, - Consumption is independent of the installed power consumption. Passive consumption in public lighting networks is caused by loss of breakers, power control circuit (timer or sensor light intensity). This group includes the consumption of the controller. Effect of harmonic voltages and currents -

distortion power Currently dominate in the public lighting networks lamps with inductive ballast. These lamps have a nonlinear VA characteristic and non-harmonic currents cause flows. Size current distortion increases with the size of voltage distortion. Undistorted power supply voltage does not occur.

Fig. 6 Sample of the current flowing in public lighting network

Fig. 7 Vector diagram of power Distorted currents cause issue distortion power which is necessary to take into account when calculating the power consumption.

[ ]VADQPS 222++=

(8)

Finally distorted currents cause increased losses, voltage distortion and greater stress of network elements. Deformed currents flows are eliminated in lamps with electronic ballasts. Harmonic generation in the LED lamps is depending on the power supply. If the power supply to the LED does not harmonics filter then generate this lamp strong distorted currents. Installed regulators

Fig. 8 Voltage and current regulation In order to reduce the consumption of network regulates power lights. Technically regulation is designed individually in lamps or in the central switchboard. Deeper analysis showed that the

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change in voltage is changing power factor and harmonic content of current. These changes are caused by changing discharge and capacitor in lamp. In the case of voltage regulation on lamps with electronic ballasts, is to some extent this regulation is ineffective. Some newer regulators do not change only the amplitude but also the supply voltage waveform. In such cases, it is strongly influenced by the current flowing deformation in lamps. Load assymetry

From several measurements carried out in the elderly and reconstructed networks indicated that the load unbalance is a common phenomenon. In terms of power quality is not a danger. Does not even increased operating costs, because depending on the distribution network is small unbalance charging customers. Load asymmetry in new networks is caused by the irresponsible connecting lights to different phases. Except the problem with uneven lighting pronounced in case of failure of one phase may be a problem with overloading phase, because the design is considered with uniform distribution. Very significantly, this problem is seen from measurements in Galante, where all the lights are connected to one phase even if the divorce was made the new three-phase cable. If the new networks connecting the unevenness caused by irresponsible lighting are very large, it may lead to switch off fusing the line.

4 Conclusion In determining consumption in public lighting networks, it is important to first determine whether the assessed immediate consumption or annual. Solving immediate consumption is easier to take into account, however, setting the operating time. When comparing the calculated values with the measured then differences may exist due to other influences such as: - connecting other devices (phone box lighting, buildings ilumination, fountains power source) - connecting a special occasional light (Christmas decoration, lighting used during holiday) Because the measurements obtained during the large amount of data, the results are still analyzed readings. For solving power balance network of public lighting with LED lighting are not some of the problems. Also in these luminaires can be clearly defined behavior when a certain voltage. In this case, you can build a network model and make a calculation taking into account the most impact.

Acknowledgement This paper was supported by the Slovak Research and Development Agency under the contract No. APVV-0280-10 Integrated Analysis of the Solar Power Plants.

This paper was supported by the agency VEGA MŠVVaŠ SR under Grant No. 1/1100/12.

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