Svetlana Beryozkina

Stochastic optimization of power line design

During the recent years, power industries have been facing significant changes due to deregulation and liberalization of the energy markets and increase of the installed capacity of renewable energy sources. These factors directly affect the transmission network planning (TNP) task and inspire a search for new, more adequate methods. This paper compares a deterministic method - the economic intervals (EI) method - and the stochastic approach based (SAB) method. Both methods are used for designing the overhead power line (OHPL), choosing the optimum conductor type and cross-section as well as other main line parameters such as the height, type and coordinates of towers, the line route, the line fittings, etc. Moreover, the paper presents a new approach for implementing a stochastic optimization procedure with a statistical representation of the electricity prices, ambient temperature and load currents in the transmission network. The problem is formulated as minimization of the total annual costs for the transmission line (TL) construction project. The tool is implemented in MATLAB software by using the Monte Carlo (MC) method as well as in OHPL designing software - PLSCADD.

Testing thermal rating methods for the overhead high voltage line

Due to the limited capacity of the existing transmission lines, new advanced technologies are implemented towards the Smart Grid. Here the interest is in the overhead line thermal monitoring systems, which are generally designed based on the existing methodologies by using the limiting conditions for the determination of the ampacity of power lines. Thus, the evaluation of commonly used thermal rating methods, which include estimation of the conductor temperature as well as the conductor sag, is quite a topical objective, which should by all means be discussed. The paper presents a comparative assessment of the measured and calculated steady-state conductor temperatures as well as line sagging, on the basis of which the testing of thermal rating methods was conducted. The experimental measurements were done using special monitoring equipment in weather conditions under cases “A” and “B” based on the existing lines of the Latvian power network. The obtained results are reviewed in this paper.

Modeling of the load current of the transmission line

This paper deals with the influence of changes in transmission line maximum conductor temperature and load current depending on conductor type and climate conditions. The theoretical backgrounds of the allowable conductor temperature as well as load current determination principles are proposed. The simulation tasks were based on a specific line model. The results of the obtained data are presented.

Stochastic planning of distribution lines

The distribution line planning task has become more complex due to several impacting factors. This paper presents a stochastic approach for implementing an optimization procedure with a statistical representation of the electricity prices, ambient temperature and load currents in the distribution network. The validation of this stochastic approach is based on the comparison results of both examined approaches (stochastic and deterministic), which are applied for the computation of the total average annual costs. Attention has been focused on reducing total average annual costs by optimizing the conductor profile of a power line and the transformer capacity. Thus, the Net Present Value of the total average annual costs can be evaluated during the planning period. The problem is formulated as a minimization of the Net Present Value of the total average annual costs of an examined distribution line project. The tool is implemented in MATLAB software by using the Monte Carlo method. The proposed stochastic approach has been applied in the solution of an example of a distribution line project, which is presented.

The stochastic approach for conductor selection in transmission line development projects

A stochastic approach is proposed for selecting the overhead line cross-sections that would be optimal taking into account the electricity market conditions. For this purpose, several conductor types with different conductor cross-sections were considered including the High Temperature Low Sag conductor types such as ACCC and ACCR, which are a part of the advanced technology. The total capital costs depending on the technical aspects were estimated as well. The paper proposes a method that minimizes the average value of the annual costs for the construction of a line based on a statistical representation of the electric power prices, the ambient temperature and the electrical current loads in the electrical networks. The use of the Monte-Carlo method and the mentioned statistical data allow the synthesis of a user-friendly algorithm to solve this problem. As an example of the stochastic approach, the 330 kV transmission line was selected. The solution tasks are done in the MATLAB and “SAPR LEP” software.

Research and simulation of overhead power line uprating using advanced conductors

Due to the deregulation of the electricity market around the world as well as the great impact of renewable energy sources and climate change patterns, uprating of existing overhead power lines (OHPL) has become more popular. There are several methods that are widely used to uprate power lines (PL), but most of them are expensive. However, the use of the advanced conductors such as High Temperature Low Sag conductors (HTLSCs) could provide various technical and economical advantages for an effective operation of the PL. This paper presents the comparison results of both the traditional type conductors and HTLS conductors based on the evaluation of the line thermal rating (LTR) under several sets of local ambient conditions. These computations have been conducted on the basis of IEEE and CIGRE ampacity standards by using PLS-CADD software.

Cost-benefit analysis of simplified substations: A case study based on the Latvian conditions

The increased requirements regarding the quality of power supply as well as the development of the transmission and distribution power networks brings about the need to connect new consumers and generators to the already-built electric networks, and these can be situated far from the existing substations. This paper presents a cost-benefit analysis of three technical solutions including simplified substations for evaluating and choosing the optimal alternative of connecting new consumers at the pre-design stage of a project. The presented cost-benefit analysis is based on the results of a comparison of three examined solutions under four examples of calculation conditions. The average annual costs have to be minimized. Thus, the selection of a rationally substantiated electric layout for connecting the new consumers is an important issue that must be taken into account for meeting the necessary future grid challenges more effectively and economically.

Optimal territory of renewable fuel collection for cogeneration plant

Secure and long-term supplies of low-cost feedstocks are critical to the economics of biomass power plants. Provided that the distribution of electricity and heat infrastructure already exists, cogeneration plant (CHP) costs depend mainly on the investment, biomass distribution density and price as well as biomass transportation cost. On sufficiently large space it is possible to operate with the average values of biomass density. The cost of transportation depends on the size of biomass collection territory, which monotonically increases with collection territory growth. The benefit index - ratio of CHP income to expanses - is the maximum at some optimum value of the territory. Proposed model of transportation cost allows optimizing the size of territory feeding the cogeneration plant with biomass.

A stochastic approach to the feasibility study for overhead power lines

This paper presents a stochastic optimization approach to the feasibility study for power lines, taking into account market conditions. To validate the proposed stochastic approach, an economic comparison of several power line design alternatives has been done, considering technical issues as well. The final evaluation and analysis was based on the results obtained by applying both approaches: the deterministic (classical) method and the stochastic one. Both methods are used for power line design including optimum selection of the main parameters of the line such as tower height, type and coordinates, conductor type and cross-section, line fittings etc. The optimization problem is formulated as minimization of the total annual operating and construction costs. The solution task is realized in MATLAB software by using the Monte Carlo method as well as in the overhead power line automation design system PLS-CADD.

Designing a transmission line using Pareto approach

Transmission networks are facing an investment challenge due to the limited capacity of the existing power lines. Construction of the new overhead lines is associated with several legal, technical and economic problems. This paper describes Pareto approach for choosing the optimum design of the power line by minimizing the invested capital costs and maximizing the net present value. The analysis of presented solution including assessment of technical and economic efficiency is based on the model of a real line project. The results of the analysis are discussed in the paper.