Ranko Goić

Power Loss Computation in High-current Generator Bus Ducts of Rectangular Cross-section

Abstract Due to the medium voltage level of generator terminals and very high-current output, generator connection to the step-up transformer is often carried out with a so-called high-current air-insulated bus duct system. Due to these high currents, during normal generator operation, accompanying Joule power losses are often very high, which in turn, results in excessive (and even non-permissive) heating of the bus duct system. The solution to the mentioned power loss problem involves a determination of currents in phase conductors and in the shield of the metal-enclosed bus duct system. A bus duct transmission line consists of either a segregated or a non-segregated air-insulated three-phase system. Phase conductors and metal enclosures are both rectangular in cross-section. Here, the developed computation model is based on the conductor filament method with application of the geometric mean distance method. It takes into account both skin effect and proximity effects, as well as complete electromagnetic coupling between phase conductors and metal enclosure.

An optimal electricity allocation model for the effective utilisation of energy sources in India with focus on biofuels.

Energy is a vital input for social and economic development of any country. With increasing agricultural and industrial activities in the country, the demand for energy is also rising. Renewable energy sources are likely to play a major role in meeting the future energy requirement of a developing country like India. Among the various renewable energy sources, the bio-energy plays a key role for the power generation. The current availability of biomass in India is estimated at about 120-150 million MT/annum covering agricultural and forestry residues corresponding to a potential of 16, 000 MW. This apart, 5000 MW can be installed through bagasse cogeneration. Plantations on wastelands also provide significant opportunity - about 62, 000 MW for grid-interactive power and another 15, 000 MW for off-grid applications. The effect of introducing renewable energy sources on the commercial energy scene has to be analyzed carefully. Development of an electricity allocation model will help in the proper allocation of the energy sources in meeting the future electricity demand in India. In this paper, an attempt has been made to develop a fuzzy based linear programming Optimal Electricity Allocation Model (OEAM) that minimizes the cost and determines the optimum allocation of different energy sources for the centralized and decentralized power generation in India with special emphasis to bio-energy. The potential of energy sources, energy demand, efficiency of the energy systems, emission released by the energy systems and carbon tax for the emissions released by each systems are the main factors which will influence the pattern of energy distribution and are used as constraints in the model. The model allocates the energy distribution pattern for the year 2020 in India, which would be helpful for policy makers in commercializing the renewable energy systems to the greatest extent. The model is made to run in MATLAB and the energy distribution pattern is obtained. The results indicate that the energy distribution pattern would be 15800 GWh (4 %) from the coal based plants, 85400 GWh (20 %) from the nuclear plants, 191100 GWh (44 %) from the hydro plants, 22400 GWh (5 %) from the wind turbine generators, 45520 GWh (11 %) from the biomass gasifier plants, 14112 GWh (3 %) from the biogas plants, 8400 GWh (2 %) from the solid waste, 33600 GWh (8 %) from the cogeneration plants and 11970 GWh (3 %) from the mini hydel plants, respectively for the year 2020. From the allocation it is understood that the bio-energy sources contributes around 22 % of the total power generation. Various scenarios are developed by varying the cost and potential of bio-fuels. A sensitivity analysis has been done to validate the OEAM model. This study will help in the formation of strategies for effective utilization of energy sources in India.

Forecasting of Coal Consumption Using an Artificial Neural Network and Comparison with Various Forecasting Techniques

Abstract The forecasting of energy consumption is essential for any country to study its future energy demand and to formulate necessary government policies. This article presents the formulation of forecasting models for the prediction of coal consumption in various sectors, such as domestic, transportation, power, and other sectors including the total coal consumption in India. A new system of forecasting a model based on the artificial neural network (univariate and multivariate) has been developed, which is a refinement on the classical time series models. The objective of the present work is to formulate the neural network model to forecast coal consumption and to compare it with the regression models. The forecast of total coal consumption in India for the years 2010, 2020, and 2030 was predicted to be 695,518, 890,143, and 1,594,844 thousand tons, respectively. The actual coal consumption data is used to validate the different forecasting models and it is found that the artificial neural network model gives better results in most of the cases.

Voltage dips influence zone and propagation through the industrial facility

Voltage dips and short interruptions are mainly caused by the short circuit in transmission and distribution network. In this paper it is given the calculation of short circuits influence zone in transmission network affecting the depth of voltage dip in the examined node. There is also given the calculation of voltage dip propagation inside the examined industrial facility for the case of one-phase short circuit. The check of the influence zone and voltage dip propagation is experimental confirmed by measurements made in one-month period.

Determining currents of cable sheaths by means of current load factor and current reduction factor

A new method for determining sheath currents as the consequence of electromagnetic coupling during line-to-ground short circuit is described in this article. This method is based on using both the current load factor and the current reduction factor. The model cables are selected to represent major constructions encountered in practice. The cable line consists of three single-core cables laid in trefoil formation and touching each other. Cable sheaths are grounded at both ends. Current load factor and current reduction factor are characteristic data of the analyzed cable line. The method presented in this paper is easy to use.

Wind power plant as ancillary service provider

Rapid growth of wind power sector presents great challenge for power system operators in aspect of generation scheduling, grid management, balancing and ancillary services. Traditionally ancillary services are obtained from conventional power plants. However nowadays, through different set of control possibilities, wind power plants are able to partly participate in provision of ancillary services. This paper discusses the possibilities of providing ancillary system services by wind power plants, primarily regarding reactive power control and partially frequency control. In addition, real example is used to demonstrate the benefits from reactive power support by wind power plant to maintain regular voltage conditions in distribution network.

Transient analysis of ring shaped grounding electrode using isoparametric quadratic elements

The paper deals with transient analysis of ring shaped grounding electrodes using isoperametric quadratic elements. The formulation in the frequency domain is based on the thin wire antenna theory and the related Pocklington integro-differential equation while the corresponding transient response is obtained by means of the Inverse Fourier Transform (IFT). The Pocklington integro-differential equation is solved by the Galerkin-Bubnov Indirect Boundary Element Method (GB-IBEM) featuring the use of isoparametric quadratic elements for the current distribution approximation.

Software package for short-term planning of the Croatian power system

This paper presents software for the short-term operative planning of the Croatian power system, based on the simulation principle, including some optimization modules. The software is designed in such a way that it enables a simple and quick making of different variants of the daily power system schedule. It also enables an improvement on all functions as well as the superstructure and redesigning, which will make possible the undisturbed functioning of the operative planning in the Croatian power system during the process of restructuring, deregulation and privatization.

The impact of flywheel torque of refurbished generator units on the limit switching time in Croatian power system

In a refurbishment project, possible solutions for old generators in Zakucac and Peruca hydroelectric power plants (HPP), Croatia, are suggested. In the first step, transient processes caused by 3-phase and phase-earth short circuits on all connected transmission lines to Zakucac and Peruca HPPs were analysed on the different power system models. Many computer calculations of transient stability in Zakucac and Peruca HPP and dependent environment of the power system with refurbished generators in these plants were made. Since transient stability in the power system with recommended characteristics of refurbished generator units were satisfied, the impacts of smaller flywheel torque on limit switching time values were considered in a second step.