ŠTUMBERGER, G.
U-5-ENERGY MANAGEMENT PLANNING IN CASE OF ELECTRIC ENERGY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 000
PINTARIČ, M., ROŠER, M., ŠTUMBERGER, G.
Optimization of Distribution Network Operation Based on Reconnection, Clossed-Loop Operation and Reactive Power Generation – A Case Study
KOMUNALNA ENERGETIKA / POWER ENGINERING, 221
The paper deals with problems of increasing the load in the distribution network that already operates near the limit load. Optimization procedure with reconnections, operation in loop and reactive power generation is being used to determinate maximal acceptable load. All analyses are made with program for load flow calculations. This paper shows results of the load flow calculations on the existing distribution network. Maximal power of two industrial consumers, which want to increase their power, was calculated based on the maximal load of the network without considering distribution generation. Operation of network in loop is also analyzed at normal network load and at maximal load. Solution to problem of too high voltage in the network, because of big distribution generation, is presented.
SKORNŠEK, M., ŠTUMBERGER, G.
Algoritem for Predicting Solar Power Plant Output Power with an Artificial Neural Network
KOMUNALNA ENERGETIKA / POWER ENGINERING, 229
This work deals with the comparison of operating propertis of photovoltaic power plants. All derogations in the operation of photovoltaic power plant can be monitored with additional measurements of solar irradiation and temperature of photovoltaic cells. Based on data acquired during six months operation of discussed photovoltaic power plant an Artificial Neural Network (ANN) has been built in order to predict output power of the power plant. The ANN complements the already existing monitoring system. When the difference between the ANN predicted and measured output power of the photovoltaic power plant is too high, a detail check of the power plant components is required.
ŠTUMBERGER, G.
KOMUNALNA ENERGETIKA / POWER ENGINERING, 5
SUKIČ, P., RODIČ, M., ŠTUMBERGER, G.
ADAPTING CAR CHARGING STATION TO PV PLANT OUTPUT POWER
KOMUNALNA ENERGETIKA / POWER ENGINERING, 31
The increasing number of PV systems increases also their influence on the electricity network in which they are connected. The PV systems operation has often a negative impact on the network voltage profile. Fluctuation of clouds causes a step decrease of a solar irradiation and subsequently leads to drastically changes in PV system’s output power in a very short period of time. In areas with a high concentration of PV systems it is to expect the drop of network voltage or even frequency. Problems related to step changes in output power of PV systems are usually solved by using energy storage devices, which are capable to compensate the output power changes.
Simultaneously with PV systems charging stations for electrical vehicle appeared in electricity networks. The most powerful chargers achieve a power up to 120 kW per installed unit and represent a heavy load in comparison to other loads connected to the network in vicinity. In case of a step reduction in PV system’s output power it is possible to lower the charging of electrical vehicles during the transient behaviour in order reduce the overall impact on the electricity network.
The paper presents simulation of the PV system disturbance compensation with the temporary decrease in charging power of vehicle connected to the charging station. The results presented show that the proposed compensation can improve voltage profile in the electricity network.
SREĆKOVIĆ, N., TRBUŠIČ, M., BELIČ, E., ŠTUMBERGER, G.
PROVIDING THE PROPER VOLTAGE PROFILES WITHIN THE MEDIUM VOLTAGE DISTRIBUTION NETWORK WITH PV SYSTEMS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 32
Proliferation of the distributed electric power generation (DG) units requires the evaluation of different effects that DG units may have on the electricity network operation. Photovoltaic (PV) systems that are properly placed and sized, as well as equipped with the suitable control systems, may have positive impact on the voltage profiles and the reduction of losses of electric energy within the network. This paper discusses the possibility of providing the proper voltage profiles within the medium voltage distribution network, using the optimal reactive power generation and/or optimal reduction of active power generation from PV systems. Time – discrete calculation of the network operating conditions throughout the year were performed on two existing medium voltage distribution networks. Optimal values of reactive power generation and the reduction of active power generation were determined using the differential evolution in time points, where voltage rise, higher than the allowed, occurred. The results obtained suggest that reactive power generation from the existing PV systems should be used in voltage control, followed by the reduction of active power generation when necessary.
BELIČ, E., VOH, J., SUKIČ, P., ŠTUMBERGER, G.
IMPACT OF PHOTOVOLTAIC SYSTEMS’ REACTIVE POWER GENERATION ON ACTIVE POWER GENERATION AND TRANSMISSION LOSSES IN
THE LOW VOLTAGE DISTRIBUTION NETWORK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 33
This paper evaluates the impact of photovoltaic systems’ reactive power generation on active power generation and transmission losses in the low voltage distribution network. The introduced experimental system consists of two major parts. The photovoltaic system represents the first part, in which every photovoltaic module is connected to the low voltage network by the individual microinverter. Two way communication is established to each microinverter by the communication gateway. The second part consists of a control system with data acquisition system. The flexible experimental system offers a possibility to add and establish different network connections of the single-phase or three-phase smart grids. Within the scope of this work, additional cable was installed to establish one phase low voltage network with the photovoltaic system on one side and network on the other. The results of the analysis and measurements performed for operation of experimental low voltage network show that the reactive power generation in photovoltaic systems increases the amount of active power that can be generated in photovoltaic systems without to violate voltage profile. However, with both of these actions transmission losses in the low voltage network increase.
ŠTUMBERGER, G.
»CO-OPERATION OF SCIENTIFIC-RESEARCH SPHERE, ECONOMY AND LOCAL COMMUNITY IN FIELD OF POWER ENGINEERING«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 2
BELE, A., DEŽELAK, K., ŠTUMBERGER, G.
MODELLING OF DOUBLE-CIRCUIT OVERHEAD LINE WITH TWO CONDUCTOR BUNDLE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 13
Proposed paper deals with the development of the double-circuit overhead power line model with the two-conductor bundle – with so called "advanced model". The results obtained by proposed model are compared with the results given in the study titled "Mutual influences within the several circuits of overhead line" and results obtained by so-called "equivalent model". The equations for capacitance, inductance and resistance calculations are presented, as well. Finally, the advanced model was used for calculations of induced voltages in the case of overhead power line Beričevo–Krško.
DEŽELAK, K., JAKL, F., MARUŠA, R., PIHLER, J., ŠTUMBERGER, G.
IMPACT OF NON-ELASTIC EXTENSION OF CONDUCTORS ON THE OVERHEAD POWER LINE CONDUCTOR SAGS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 14
Proposed paper deals with the problems regarding a non-elastic elongation of overhead conductors known as creep phenomena on account of mechanical yielding of material. Impact of non-elastic elongations of conductors is directly connected with the conductor sags and with smaller clearances between conductors and ground. Some results related to the researches in permanent elongations of conductors of the ACSR 490/65 type are presented, where compesation methods are applied as well.
SUKIČ, P., ŠTUMBERGER, G.
ELECTRICAL ENERGY STORAGE AND CURRENT SITUATION OF ELECTRICAL ENERGY STORAGE IN GERMANY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 23
New era of investment in renewables began in the last year. Due to technical needs for energy storage and network regulation, as well as government grants, Germany began developing energy storage systems for personal use and commercial purposes. Current battery storage systems based on lithium cells have efficiency of ~ 86%, with price per unit of installed power capacity ~1 €/W/Wh, and dropping. Year 2016 is expected to be a landmark year for electrical energy storage systems, as it is assumed that prices of electricity from solar power and energy storage system (with grant included) will reach the price of electricity from the electric grid. This paper presents current technical and economic state of energy storage systems for various needs.
SUKIČ, P., ŠTUMBERGER, G.
GENERATION OF REACTIVE POWER WITH SOLAR POWER PLANTS AND EXAMPLES OF IMPROPER OPERATION OF SOLAR POWER
KOMUNALNA ENERGETIKA / POWER ENGINERING, 30
The article discusses the generation of reactive power with solar power plants. Discussed is the impact of reactive power generation on the efficiency of solar inverter. Throughout the year solar power plants operate with maximum power only in short time intervals. Therefore it is possible to generate large amounts of reactive power with solar power inverters, if needed. Due to improper operation of solar power plants, anomalies in the distribution network occur. This paper presents some of these anomalies.
SREĆKOVIĆ, N., ŠTUMBERGER, G.
INFLUENCE OF ADDITIONAL PHOTOVOLTAIC UNITS ON ENERGY SAVINGS IN THE PART OF THE MIDDLE-VOLTAGE NETWORK IN MARIBOR
KOMUNALNA ENERGETIKA / POWER ENGINERING, 31
With higher penetration of distributed generation units in the distribution network, it has become important to evaluate their influence on network operating conditions. The paper analyzes the influence of active and reactive power generation of additional photovoltaic (PV) units in the part of the middle-voltage network in Maribor. Based on assessment of buildings’ roof PV potential, the most suitable roofs for PV system installation and their influence on yearly energy savings have been determined. The results show the energy savings achieved, due to the power loss reduction, obtained by the additional PV unit installation. Furthermore, energy savings achieved through proper reactive power generation are evaluated as well.
BELIČ, E., DEŽAN, K., LUKAČ, N., ŠTUMBERGER, G.
EVALUATION OF ENERGY SAVINGS ACHIEVED WITH OPTIMUM PHOTOVOLTAIC SYSTEMS REACTIVE POWER GENERATION IN LOW VOLTAGE DISTRIBUTION NETWORK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 32
This paper deals with the evaluation of energy savings that can be achieved in low voltage distribution network by photovoltaic systems (PVS) reactive power generation according to the network needs. Whole analysis is done on the model of real low voltage distribution network, where two 50 kWp PVS are installed. For evaluation of energy savings, time frame of one year is considered. Active powers of PVS are determined on the basis of average measured solar irradiance in half hour intervals and loads active powers on the basis of load profile. Since installed photovoltaic systems are relatively large, the analysis is also performed for smaller PVS with rated power of 5 kWp. The presented results shows, that energy savings can be achieved with existing PVS when they generate optimal reactive power. However, savings can be even improved if instead of big, smaller PVS are installed at sites where consumption is present.
ŠTUMBERGER, G.
SMART GRIDS AND SMART BUILDINGS CONNECTION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 4
SREĆKOVIĆ, N., BELIČ, E., ŠTUMBERGER, G.
COMPARISON OF METHODS FOR LOAD FLOW CALCULATION IN LOW VOLTAGE DISTRIBUTION NETWORK WITH CONNECTED DISPERSED PRODUCTION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 8
Load flow analysis represents one of the core methods used in modern distribution system operation. Therefore, it is necessary to provide efficient, numerically robust load flow algorithms with fast convergence and minimum usage of memory, suitable for variety of operating scenarios. The paper presents, compares and evaluates two efficient methods for load flow calculation in distribution network – backward/forward sweep method and direct method. The procedure of modeling the distribution network elements – line sections, loads, distributed generation units, as well as the implementation of algorithms, has been presented. The analysis has been performed on low voltage distribution network system.
BELIČ, E., DEŽELAK, K., ŠTUMBERGER, G.
A LINE VOLTAGE DEPENDENCY ANALYSIS ON ACTIVE AND REACTIVE POWER FLOW AT DIFFERENTC LOW VOLTAGE LINES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 9
The paper provided presents a line voltage dependency analysis on active and reactive power flow. The line voltage dependency is studied based on analytical expression. For the analysis it is assumed that one end of the line is connected to infinite bus, while at the other end voltage is observed in dependency of active and reactive power flow. The analysis covers three different low voltage cables with two different lengths. The results shows that in low voltage network voltage significantly depends on active power flow, while reactive power flow dependency is minimal. Voltage dependency increases, when low voltage lines are extended.
SUKIČ, P., DREVENŠEK, D., BELIČ, E., ŠTUMBERGER, G.
EFFICIENCY OF INVERTERS IN SOLAR POWER PLANTS WITH REACTIVE POWER GENERATION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 14
The paper discusses possibilities for reactive power generation using inverters for solar power plants. Measurements performed on an inverter for solar systems were performed for different values of generated active and reactive power in order to determine the efficiency characteristic. The obtained characteristic is approximated with a surface. It is applied to evaluate increase of inverter losses due to reactive power generation as well as to evaluate the potential of inverters in solar power plants for reactive power generation.
ROŠER, M., ŠKOF, R., ŠTUMBERGER, G.
EARTH FAULT IN MEDIUM VOLTAGE DISTRIBUTION NETWORKS WITH RESONANT NEUTRAL EARTHING
KOMUNALNA ENERGETIKA / POWER ENGINERING, 19
Reliability of electricity supply is directly related to the supply interruptions, mostly caused by earth faults that appear in medium voltage distribution networks. One of very effective measures, that can substantially reduce the supply interruptions due to the earth fault in medium voltage distribution networks, is resonant neutral earthing. It compensates capacitive currents and reduces the current flowing through the fault which establishes better conditions for arc self-extinguishing at the earth fault location. The paper deals with conditions at the location where vegetation touches the conductor and establishes an earth fault. The results of field-testing performed in substation Krško, where earth faults were established under controlled conditions, using specially for this purpose build mechanical device, are presented and discussed.
DEŽELAK, K., KOTNIK, S., DEŽAN, K., BELIČ, E., IVANECKÝ, J., ŠTUMBERGER, G.
ACCEPTANCE INDICATORS OF A MICRO HYDRO POWER PLANT INVESTMENT FOR A MICRO HYDRO POWER PLANT "KOTNIK"
KOMUNALNA ENERGETIKA / POWER ENGINERING, 5
This paper deals with the impact of the energy cost, produced by a micro hydro power plant, on the acceptance indicators of a micro hydro power plant investment. The aforementioned acceptance indicators are the net present value and the internal rate of return. All calculations are performed for a micro hydro power plant "Kotnik" with power of 10 kW, where technical and essentially financial parts are observed.
SEME, S., DEŽAN, K., ŠTUMBERGER, G.
ECONOMIC PARAMETERS OF PHOTOVOLTAIC SYSTEMS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 6
This work deals with economic parameters of photovoltaic systems. Economic parameters are important for the calculation of the investment in the photovoltaic systems. The parameters for the calculation of the technical and financial evaluations of the investment are presented. The technical calculation is affected by parameters, such as, manner, position, size of the system, the materials of the modules, inverters and electric energy produced by the photovoltaic system. For evaluating the investment technical and financial calculations are important. It is necessary to assess the initial investment costs, annual maintenance and operational costs, and also the redemption price of electric energy. The evaluation of investment costs and consequently income from electric energy sales are required for understanding the basics of the economics of photovoltaic systems.
DEŽELAK, K., JAKL, F., BELIČ, E., ŠTUMBERGER, G.
EMISSIONS OF ELECTRIC AND MAGNETIC FIELDS CAUSED BY 400 KV OVERHEAD POWER LINES TYPE DONAVA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 8
In proposed paper the emissions of electric and magnetic fields caused by 400 kV overhead power lines type Donava are dealt. Firstly, the classical Donava type overhead power line is dealt, while different varity of conductor bundle are considered. Secondly, the Austrian type of overhead line is considered, firstly without and after with additional 110 kV system on the same tower.
BELIČ, E., SUKIČ, P., DEŽELAK, K., ŠTUMBERGER, G.
DYNAMICAL MODEL OF DISTRIBUTION NETWORK WITH DISTRIBUTED GENERATION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 18
In this paper a dynamical model of distribution network with distributed generation is presented. Model of distribution network was developed using software package Matlab/Simulink with its blockset SymPowerSystems. Elements of utility network like supply network, power lines, load, and distribution transformer were modeled with elements which are already included in this blockset, but the distributed generator model was developed based on the current injection to the grid, considering references of active and reactive power. The aim of network modeling was to analyze the voltage profiles and transmission loses before and after connection of the distributed generation to the grid. Presented are the results of performed analysis.
IVANECKÝ, J., DEŽELAK, K., ŠTUMBERGER, G.
CONCEPT OF VIRTUAL POWER PLANT PARTICIPATION IN THE SLOVAKIAN ELECTRICITY MARKET
KOMUNALNA ENERGETIKA / POWER ENGINERING, 21
The proposed paper deals with a Virtual Power Plant (VPP) concept in the Slovakian electricity environment. The first part of paper explains the concept of VPP and also the reasons why is worth dealing with this concept. The second part of the paper briefly describes the market environment in the Slovakian power system, as well as methodology within individual constraints related to the operation of individual sources are considered.
ROPOŠA, S., ŠTUMBERGER, G.
»SMARTGRIDS IMPLEMENTATION IN THE CASE OF ELEKTRO MARIBOR«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 5
Limited sources of fossil fuels and emissions of greenhouse gases related with the combustion of these fuels force use to increase the use of renewable energy sources. Unfortunately, the renewable energy sources are often distributed in the space and are not always available. Technical solutions for utilization of renewable energy sources are relatively expensive while the cost of energy, produced in this way, are too high to be economically bearable without national support schemes.
In spite of aforementioned drawbacks, European Union and Slovenia have made political decisions to support energy production from renewable energy sources. The electrical power generation based on renewable energy sources in Slovenia is focused on utilization of sun energy, water energy and biomass. A substantial increase in the number of installed electric power generation units, based on renewable energy sources, has been reported the last years. The share of photovoltaic power plants is dominant. It must be pointed out that the power system, as well as the transmission and distribution networks, were designed and build considering the energy flow from the power plants towards consumers. However, the increasing share of distributed electrical power generation units, connected to the electricity network, can change the direction and increase the dynamics of changes in the power flow. Such operation could cause problems in the electricity networks not designed for that kind of operation. The solution called SmartGrids should help to solve problems, related with the increased share of distributed power generation connected to the electricity networks.
SEME, S., ŠTUMBERGER, G.
EFFICIENCY OF SILICON SOLAR MODULES AT DIFFERENT CLIMATIC CONDITIONS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 7
This paper deals with the impact of different climatic conditions on the efficiency of silicon solar modules. The mono-crystalline, the poly-crystalline and the amorphous silicon solar modules are compared. According to the measurements of IU characteristic of the solar module and solar radiation, the efficiency of individual silicon solar modules has been determined. It is shown that the efficiency as a function of different climatic conditions for a silicon solar modules varies considerably. Slowly increasing efficiency characteristic as a function of intensity of solar radiation is shown in amorphous silicon solar modules, while the poly-crystalline and mono-crystalline silicon solar modules, this characteristic is flat.
DEŽELAK, K., DEŽAN, K., DEŽELAK, D., BELIČ, E., ŠTUMBERGER, G.
INTERNAL RATE OF RETURN FOR A SOLAR POWER PLANT IN CASE OF MOVABLE PHOTOVOLTAIC MODULS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 8
In proposed paper the internal rate of return for a solar power plant investment is mainly dealt. The main parts of the solar power plant are represented by the photovoltaic moduls, which could be static or movable. In case of movable photovoltaic moduls, where moduls are following to the movement of the sun, the amount of the produced energy could be even up to 30 % higher than in case of static photovoltaic moduls. On the other hand an investment in movable solar plant leads to the higher initial costs of the whole investment.
DEŽELAK, K., PIHLER, J., FLUHER, B., ŠTUMBERGER, G.
COMPARISON OF SMALL HYDRO POWER PLANTS: HYDRO MATRIX TURBINE VS. MOVING HYDRO POWER PLANT
KOMUNALNA ENERGETIKA / POWER ENGINERING, 11
In proposed paper the comparison of two possible solutions for small hydro power plant construction is dealt. In that way the technical, as well as financial parts are observed. The first proposed solution is hydro power plant with the hydro matrix turbine, whilst the second solution is construction of so called moving hydro power plant. The choice of such solutions depends on particular water flow.
ČERNELIČ, J., ŠTUMBERGER, G.
LABORATORY PROTOTYPE OF A STATIC VAR COMPENSATOR
KOMUNALNA ENERGETIKA / POWER ENGINERING, 13
This paper presents a design of a laboratory prototype of a static var compensator. Compensator is made of a DC-link, two-stage three-phase inverter and passive LCL filter. For control, Voltage oriented control with PI regulators is used, along with space vector pulse-width modulation. Results of the experiment have shown appropriate design and good responses in transient conditions.
LUKAČ, N., ŽLAUS, D., SEME, S., ŽALIK, B., ŠTUMBERGER, G.
METHOD FOR ESTIMATING ROOFS SOLAR POTENTIAL CALCULATED ON LIDAR DATA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 23
Buildings' roofs are becoming increasingly important for photovoltaic systems installation. They can increase efficiency of electrical usage and decrease the amount of greenhouse emissions. However, not all roofs are suitable for photovoltaic systems installation. This work proposes a method for estimating roofs’ solar potential. The solar potential is calculated on LiDAR data using measurements of direct and diffuse solar irradiance from pyranometer at a given location. Multiresolutional shadowing is proposed for achieving higher accuracy in the solar potential calculation.
CERKOVNIK, U., ŠTUMBERGER, G.
ENERGY SELF-SUFFICIENT STREET LIGHTS (ESUS)
KOMUNALNA ENERGETIKA / POWER ENGINERING, 25
Within diploma work "The impact of street lights on energy transmission losses and possibility for realization of energy self-sufficient street lighting" were constructed two examples of energy self-sufficient street lights (ESUS). The lamp is not connected to the electricity grid and for its normal operation use energy from the wind and sun. At the top of the street pole is mounted vertical axis wind generator, which begins to operate at very low wind speeds (2-3 m/s). On the circumference of the pole is installed thin film solar panel that generate solar energy throughout the day. Possibility of installed passive infrared motion sensors and GSM monitoring and management system results as reducing electricity consumption of street lamp up to 80 percent.
PLANTIĆ, Ž., ŠTUMBERGER, G.
ENERGY SAVING HIGH EFFICIENT FANS AND BLOWERS DRIVEN BY PERMANENT MAGNET SYNCHRONOUS MACHINE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 5
This paper deals with the energy saving high efficient fans and blowers driven by permanent magnet synchronous machine (PMSM). In order to improve the efficiency of fans and blower, the losses due to the non-optimal operation should be minimized. A proper control of the PMSM can help to reach this goal. The fans an blower often operate under operating conditions where operation without position sensor is desired. In such cases the rotor position required in the PMSM control can be determined using appropriate models and measured currents and voltages, which leads to the sensorless control realizations. Successful implementation of the sensorless control requires a very good knowledge of PMSM parameters. Some of the methods appropriate for their determination are discussed in this paper.
DEŽELAK, K., OGOREVC, K., ŠTUMBERGER, G.
COMPARISON OF HYDROELECTRIC POWER PLANTS BOŠTANJ AND BLANCA
KOMUNALNA ENERGETIKA / POWER ENGINERING, 9
This paper presents a comparison between two hydroelectric power plants (HEPP), HEPP Boštanj and HEPP Blanca. This comparison consists of two parts. The first part is based on the comparison of their dam structures with the mechanical and electric equipment installed, while the second part contains an economic analysis performed with the RETScreen software. The results of proposed analysis show the financial pointers of both hydroelectric plants.
DEŽELAK, K., DEŽELAK, D., ŠTUMBERGER, G., JAKL, F.
CALCULATION OF THE TEMPERATURE OF THE OVERHEAD POWER LINE CONDUCTOR
KOMUNALNA ENERGETIKA / POWER ENGINERING, 16
Temperature of the overhead power line conductor during operation represents one of the basic limit parameter for overhead power line operating. The allowed conductor heating must be under the limit values, because of high impact to the mechanical parameters of the conductors and conductor sagging. In the paper, all of the results are obtained with the CIGRE method, while obtained results are shown in program package Matlab.
SEME, S., ŠTUMBERGER, G., VORŠIČ, J., TOMAŽIČ, A.
MEASUREMENT OF THE U-I CHARACTERISTICS OF PHOTOVOLTAIC MODULES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 11
This paper deals with measurement of the U-I characteristics of photovoltaic modules. Measurements of the U-I characteristics of photovoltaic modules are defined in standards developed by the Technical Committee IEC TC 82. Unfortunately, we do not have equipment required to perform measurements of U-I characteristics of photovoltaic modules in accordance with the standard. Therefore, a comparative analysis of U-I characteristics measured on different modules under the same technical and weather conditions is performed. The results are given for the photovoltaic modules made of monocrystalline silicon, polycrystalline silicon and amorphous silicon.
DEŽELAK, K., KADIŠ, J., ŠTUMBERGER, G.
CALCULATION OF AUDIBLE NOISE EMISSIONS CAUSED BY HIGH VOLTAGE OVERHEAD POWER LINES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 16
The paper deals with the calculation of audible noise emissions caused by high voltage overhead power lines due to corona. The first part describes the theoretical basis of corona occurrence and its consequences. Furthermore, the paper presents frequently used methods for the calculation of audible noise emissions caused by high voltage overhead power lines. Electric field strength values around conductor are essential for audible noise emissions and the occurrence of corona, therefore, the comparison of three methods for the calculation of electric field was performed. All of the methods were used for calculating the audible noise emissions caused by various overhead power lines.