KOMUNALNA ENERGETIKA / POWER ENGINERING 2015
KOMUNALNA ENERGETIKA 2015, _.
KOMUNALNA ENERGETIKA / POWER ENGINERING, 00
KOMUNALNA ENERGETIKA 2015, _.
KOMUNALNA ENERGETIKA / POWER ENGINERING, 0
KOMUNALNA ENERGETIKA 2015, _.
KOMUNALNA ENERGETIKA / POWER ENGINERING, 000
PLAVČAK, G.
»ENERGY POLICY– PRIORITY AREAS FOR TRANSITION TO A LOW-CARBON SOCIETY«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 1
ŠTUMBERGER, G.
»CO-OPERATION OF SCIENTIFIC-RESEARCH SPHERE, ECONOMY AND LOCAL COMMUNITY IN FIELD OF POWER ENGINEERING«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 2
PODGORNIK, A.
»INDUSTRY OPPORTUNITIES IN FIELD OF POWER ENGINEERING«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 3
KRMELJ, V.
»TASKS OF ENERGY AGENCIES IN FIELD OF LOCAL COMMUNITIES POWER ENGINEERING«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 4
KOINEGG, J.
»SMARTCITY GRAZ«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 5
POGAČNIK, A.
»EXEMPLARY WORK OF LOCAL COMMUNITIES IN FIELD OD POWER ENGINEERING«
KOMUNALNA ENERGETIKA / POWER ENGINERING, 6
SRPAK, D., ŠUMIGA, I., STIJAČIĆ, S.
SOLAR POWER PLANT „STUDENTSKI RESTORAN VARAŽDIN”
KOMUNALNA ENERGETIKA / POWER ENGINERING, 7
This article describes the main elements of solar power plant built on the roof of the student restaurant in Varaždin, particular the used grid inverters. Moreover, the way of connecting the photovoltaic cells on grid converters and user’s installation is presented. At the end of this paper there is a review of electrical energy production during first five month of operation.
SOMI, L., DEŽELAK, K., PIHLER, J.
ACCUMULATION SMALL HYDRO POWER PLANT ON THE EXISTENT LAKE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 8
An article presents an Accumulation small hydro power plant on existent lake. The project could be built on an already existing infrastructure, consisting of an embankment, a tower and a lake outflow. In the paper the potential of the river Ledava in the western part of Goričko with the placement of the hydro power plant is dealt. The choice of technical equipment, location and the planned operation regime, as well as the construction and investment cost of the project are presented in the work.
TEKAVEC, S., KRMELJ, V.
ENERGY CONTRACTING IN WOODEN BIOMASS ENERGY UTILIZATION
KOMUNALNA ENERGETIKA / POWER ENGINERING, 9
Wooden biomass is becoming more and more important energy source for heating in Slovenia because it is local and cheap source and our country has large area of forest. Usage wooden biomass has positive effects such as CO2 neutral energy source, availability to all Slovenian territory and energy independence. Wood like energy source is very useful and effectible for system of remote heating which is becoming more and more used way of heating because it has low heating costs and it is independent of changing price sources. For energy renovation or building new remote heating has been established new way of funding named energy contracting. The main purpose of this funding is payment will be pay off in the time of contract. Investment, maintenance and management of heating system pay off with fixed part of costs; payment of energy sources is paid by variable part of costs like heat price. Article represents two examples good practice of energy contracting at usage wooden biomass. First good practice is Mojstrana where remote heating was renovated and there is 23,7 % saving at year and second good practice is Ribnica where 20 years old remote heating was restored.
SOVIČ, B.
PROBLEMS OF NOMINAL, INSTALLED AND BILLED POWER FOR HOUSEHOLDS AND CONSUMERS WITHOUT MEASURED POWER
KOMUNALNA ENERGETIKA / POWER ENGINERING, 10
The applicable Act for network charges inaccurately determines the installed power and allows for major discrepancies between installed and billed power.
To remedy the problems and to provide transparency, accuracy and non-discrimination for the network users, we need to accurately determine the installed power and even out the installed and billed power. This is why a unified table for power is suggested.
SOVIČ, B.
RATION OF COLLECTED ENERGY FROM DISTRIBUTION ENERGY SOURCES AND HOUSEHOLD CONSUMPTION IN CONTEXT OF NEARLY ZERO ENERGY BUILDINGS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 11
Comparison between household consumption and collection from production sources for the supply area of the electricity distribution company Elektro Maribor shows that prior to 2010, the consumption share from production sources in households was lower than a tenth per year, but then exceeded by a 30% in value by 2014. This was contributed by connecting more and more production sources to the distribution network after 2004 and a lower amount of household consumption after 2008.
To achieve the goals of nearly zero-energy buildings, it would be necessary to significantly increase the amount of electricity and heat production sources. The EU Directive 2010/31/EU and the Energy Act EZ-1 stress the importance of renewable energy sources produced on location or nearby. This places special attention to sources on buildings, including sources, which are at the same time also construction elements.
Adjusting consumption is also going to receive special attention. In this area, dynamic pricing systems could make a major contribution and advanced metering systems as a precondition for dynamic pricing.
BOGOVIČ, J., MIHALIČ, R.
MODEL OF STATIC SYNCHRONOUS SERIES COMPENSATOR
KOMUNALNA ENERGETIKA / POWER ENGINERING, 12
This paper presents a model of Static Synchronous Series Compensators (SSSC) for load-flow calculations in a distribution system for the forward-sweep algorithm. The model of SSSC for forward-sweep algorithm is based on current model used in Newton-Raphson load-flow calculations. The model is modified that is used for forward-sweep algorithm, but all known properties are preserved. Since the distribution networks are mainly radial and unequally loaded by phases, a three-phase modeling of SSSC is presented. Models are verified on a test case.
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.
VORŠIČ, Ž., KUMPERŠČAK, V., PIHLER, J.
HEATING OF CONDUCTORS IN STEADY STATE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 15
Several factors influence the choice of conductor cross-section when planning distribution and transmission networks, such as voltage drop, loss of power, stability, protection and others. Important factor is also conductor temperature rise above surrounding temperature. To determine it one must know maximum continuous current which determines maximum allowed conductor temperature. The temperature of the conductor affects the conductor sag between the pillars and determines the change in tensile strength due to heating. Conductor temperature is authoritative guide for selecting conductors for short connecting lines in extreme condition.
Three temperatures are relevant: Joule heating depends on average conductor temperature and convection and radiation depends on conductors’ surface temperature. Change (decrease) of tensile strength is in first approximation dependent on temperature of strands in the middle of conductor.
Article shows how individual influencing factors act on conductor by heating or cooling it in steady operation.
MARUŠA, R., VORŠIČ, J., PIHLER, J., KOBAL, I., MARUŠA, L.
SELECTION OF A SUITABLE CONDUCTOR FOR GROUNDING THE CABLE SHIELD TO THE TRANSMISSION LINE TOWER
KOMUNALNA ENERGETIKA / POWER ENGINERING, 16
This paper describes which factors to consider when faced with choosing conductor for grounding of surge arresters and high-voltage cables on powerline construction, where transition between powerline construction and powerline cable takes place. For proper grounding of surge arrester and shielded cable, the grounding cables have to be designed to ensure efficient high frequency current flow to the ground that can reach up to 10 kA. During our research and measurements we have chosen such a conductor that at the same time ensures recommended parameters and is not of any particular value to vandalism.
JELENC, B.
DETECTING DEFECTIVE FEEDER DURING HIGH IMPEDANCE PHASE TO EARTH FAULT IN ELECTRICAL DISTRIBUTION SYSTEM –SUBSTATION USING ARTIFICIAL INTELIGENCE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 17
Recent developments indicate that Artificial Neural Networks (ANNs) may be appropriate for assisting dispatchers in operating electric power systems. This paper presents approach to detection defective feeder during phase to earth fault (also high impedance faults) in electrical distribution system –substation using feed- forward artificial neural network (ANN).
In the ANN algorithm, the standard back-propagation technique with a sigmoid activation function is used. The proposed neural network was trained by real data recorded with Disturbance recorder during actual fault.
Performance study results show that the proposed algorithm performs very well in detecting the phase to earth fault and locating faulty feeder.
HOSNAR, J., KOVAČ KRALJ, A.
APPLICATION OF MATHEMATICAL PROGRAMMING FOR RECONSTRUCTION OF INDUSTRIAL PROCESSES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 18
Low efficiency, negative impacts on the environment and non-profitable operations are the main shortcomings of out-dated industrial power-plants. Such processes can be improved through reconstructive techniques and mathematical algorithms created as tools for systematic approaches during engineering decision-making. The study focuses on the development of a mathematical algorithm for a combined approach to the reconstruction of non-profitable industrial power-plants. The main goals of the set out mathematical algorithm are: i.) to maintain the existing process units and chemical plants to a greater extent, ii.) to enable the potential for finding new process alternatives and technological solutions, iii.) to provide a streamlined operation for all subsystems and total systems, iv.) to promote environmental and social responsibilities, and v.) to apply the concept of a reconstructive method for non-profitable chemical plants.
KRALJ, K.
WIND POWER PLANTS MODELS IN PROGRAMMING ENVIRONMENT ANALYSIS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 19
The purpose of this paper is to analyze Simulink`s program models of wind power stations. We propose to examine different types of wind farms, from squirrel cage induction generator, synchronous generator and moreover doubly fed induction generator. Firstly we have studied the parameters of each model and discovered when it can be used. Therefore we have used them for simulation of various operating states. The detailed analysis of DFIG, including phasor type and dynamic model has been conducted, while pointing out their differences.
COPOT, A., KRMELJ, V.
EXAMPLES OF GOOD PRACTICES IN THE FIELD OF ELECTRIC MOBILITY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 20
Electric mobility is becoming from an environmental point of view, more and more interesting, because it does not produce greenhouse gases. We can also drive electric vehicles with electricity produce from renewable energy sources. This means the electric bicycles, scooters and cars driven on electricity produced from renewable energy sources.
The advantages of electric cars are lower transport costs, reduce of noise Pollution, vehicles are 100 percent eco-friendly and comfortable. Number of good practices in the field of electric mobility is growing.
GOVEDIČ, B.
ELECTROMOBILITY AND DEMAND RESPONSE
KOMUNALNA ENERGETIKA / POWER ENGINERING, 21
Electro mobility may in the future help in balancing the production and consumption of electricity. The adjustment of consumption, electric vehicle charging in time of surplus energy, consequently, reduces also the peak power in the electricity system.
MARUŠA, R., BEZJAK, S., BOBIČ, T., MARUŠA, L., BUČAR, A., BELAK, L.
PRACTICAL PREPARATION OF ELECTRICAL INSTALLATION REMOTELY CONTROLLED CONSUMPTION OF ENERGY
KOMUNALNA ENERGETIKA / POWER ENGINERING, 22
Smart Grid and. smart grids are theoretically in full swing, but the practical electrical installations in the users do not adequately adapted to the technology of remote control. In this paper we moved directions and applications designed to be remotely controlled certain electricity consumers even at installations in the domestic take-up of electricity.
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.
LAVUGER, B.
UNINTERRUPTIBLE POWER SUPPLY AND THEIR ARCHITECTURES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 24
Reliable and resilient power supply is the key for the functioning of many systems and devices in different organizations. To achieve these objectives, it is not enough just to install spare and uninterruptible power supply sources. Design of reliable and resilient power supply systems require to respect some special demands and fundamental knowledge. To help in design procedure recommendation and typical architectures of such systems has been prepared. Engineers with support of this recommendations and typical architectures can relatively fast and efficient prepare end solutions with respect to all necessary end resilience. In article we will present key demands and requirements for reliable and resilient power supply systems also with typical architectures of such power supply systems.
KLASINC, D.
REGULATIONS IN ELECTRIC POWER SYSTEMS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 25
This paper represents regulations used in electric power systems. It describes operating modes of the primary, secondary and tertiary regulation in the electrical power network. This paper will describe operations of turbine governors and their impact on the electric power system. An example of network collapse including the chain of hydro power plants, as well as response of turbine governors will be presented.
HUFNAGL, E., AIGNER, M., SCHMAUTZER, E.
EVALUATION OF AN URBAN MEDIUM VOLTAGE NETWORK USING RELIABILITY INDICES
KOMUNALNA ENERGETIKA / POWER ENGINERING, 26
This article deals with the assessment of reliability indices of a medium voltage network. In order to evaluate an urban medium voltage network, several steps can be taken to determine the reliability indices describing the network in its current state, as well as for potential changes caused by e.g. reinforcement of the electrical installation, restructuring measures, increased generation and demand in the network structure. To successfully conduct the following calculations, the correct use of the input data for the created reliability datatypes and reliability values is essential. By using reliability indices an impartial comparison between various options (referring to the cited measures) is possible.
SOTLAR, T., PIHLER, J., ROŠER, M.
IMPACT OF THE GENERATOR TO SHORT-CIRCUIT CONDITIONS IN THE DISTRIBUTION NETWORK
KOMUNALNA ENERGETIKA / POWER ENGINERING, 27
The article deals with the analysis of the impact of the generator to short-circuit conditions in the distribution network. The aim is to determine the effect of synchronous generator on short-circuit currents, which are at the point of connection baseline data for the design and sizing of individual network elements. Short-circuit currents will be in point of short circuit determined using a DMS software tool that is developed for the analysis of the actual situation in the network and also enables the calculation of the parameters of all types of short circuits. Analysis of the impact of the generator to the short-circuit currents in the distribution network is carried out in point near the generator and point away from the generator by comparing the results with the generator on and off.
MALLITS, T., SCHMAUTZER, E., FICKERT, L.
REFLECTIONS ON GLOBAL EARTHING SYSTEMS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 28
On the basis of measurements it can be shown that only a portion of the phase to ground fault current enters the physical soil. Therefore the earth potential rise (EPR) is considerably decreased and the contact voltages become much lower than those determined by the usual approaches. A risk assessment method used in the UK and Australia is presented by which the corrective actions in the case of dangerous contact voltage can be determined.
HUFNAGL, E., FICKERT, L., SCHMAUTZER, E.
EFFICIENT CALCULATION OF EARTH FAULT CURRENTS IN COMPENSATED NETWORKS
KOMUNALNA ENERGETIKA / POWER ENGINERING, 29
In this paper, a simplified approach for determining the ground fault currents is presented which is specifically useful in compensated systems. In this case, due to the estimation of the relative magnitudes of the equipment parameters, the equivalent circuit in symmetrical components of the single-pole fault is significantly reduced. Thus the electrical parameters of the impedances can be directly used.
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.