Brazilian Interconnected System Research Articles

Using sampled values in line differential protection – Analyzing the scheme feasibility and protection performance under communication stress scenarios

Line differential protection features great selectivity to isolate equipment under fault conditions. However, this technique has been limited by factors such as transmission line length, communication network delay, use of proprietary protocols, or vulnerability to network failures. The IEC 61850 standard enables the implementation of digital substations, which have proven to be a good option for improving the reliability and efficiency of the electrical system. In this sense, we propose a new scheme for differential protection in transmission lines using SV messages by the IEC 61850 standard. In addition, we carry out a feasibility for differential protection in two 500 kV transmission lines of the Brazilian interconnected system using the Aspen Oneliner software. We evaluate the communication performance of the proposal in a testbed with two SEL 421–7 protection relays capable of sending and receiving SV messages, an Omicron CMC 356 test case, a PTP signal distributor device SEL-2488, an SEL-9524/GNSS antenna, switches for proper formation of communication buses, and hardware to emulate the length of the transmission line communication channel, generate concurrent traffic injection, and also induce package loss scenarios for the SV messages. The results are promising and indicate the viability of the proposal.© 2017 Elsevier Inc. All rights reserved.

Fluent Restoration Modelling Applied to a Real Power System Using Colored Petri Nets

In this article the Colored Petri Nets (CPN) and the Critical Path Method along with the Program Evaluation Review Technique (CPM/PERT) are described and their characteristics compared for application on the real-time fluent restoration of power systems. A CPN based method is proposed and has been found more suitable since it is able to represent the temporal sequencing and the logical dependency between restoration activities. The restoration planning of electrical power systems are based on a worksheet drawn up by experts, which contains a list of procedures for restoration. The restoration process has been improved and a real case study is presented using the CPN modeling applied with success to an operative fluent restoration post-outage in the Brazilian interconnected system

Combining monthly wind and inflow uncertainties in the stochastic dual dynamic programming

AbstractFollowing a global trend, intermittent sources, especially wind, have been experiencing accelerated growth in Brazil—in the last decade, wind power grew 13 times and became the second largest source in the electricity mix (12%), just behind hydropower (60%). Currently, although following regulatory guidelines, the representation of wind power in the long-term operation planning model is done in a simplified way, based on the monthly average of the last five years of aggregated generation, thus demanding improvements. The objective of this work is to describe an approach to be used by the Brazilian power industry to represent the uncertainties of monthly wind power production in the SDDP algorithm applied in the long-term operation planning model, keeping the large-scale stochastic problem still computationally viable, when applied to large interconnected systems, especially with hydroelectric predominance. The proposed methodology comprises statistical clustering of wind regimes and definition of equivalent wind farms; evaluation of monthly transfer functions between wind speed and power production; integrated generation of monthly multivariate synthetic scenarios of inflows and winds, considering associated cross-correlations; and representing monthly wind power in the SDDP algorithm. The application to real configurations of the Brazilian interconnected system, including case studies related to the monthly operation program and the calculation of the maximum amount of energy that can be traded in long-term power purchase agreements, points to its effectiveness and the relevance of modeling the wind uncertainties in the long-term operation planning of large hydro-dominated systems.

Mathematical and experimental evaluation of an incremental differential protection function embedded in a real transmission line relay

This paper evaluates, mathematically and experimentally, a transmission line differential protection function based on incremental currents, which are not influenced by pre-fault conditions, such as charging and loading levels. In the mathematical analysis, the trajectories for each phase, for all types of faults, are demonstrated by analytic deduction of incremental current ratios. For the experimental assessment, the Alternative Transients Program (ATP) was employed to submit a 500 kV 200 km long transmission line into a wide variety of faults. In addition, a 500 kV transmission line of the Brazilian interconnected system was also modeled via ATP, so that different faults scenarios could be applied to it. Also, for this last set of cases, the algorithm was embedded into a real commercially available relay to assess its performance. In order to carry out a broad evaluation of the incremental algorithm performance, sensitivity analyses were made. The results reveal that the incremental function operates for a bigger variety of faults including ones that the conventional function does not operate.

Modeling coordinated operation of multiple hydropower reservoirs at a continental scale using artificial neural network: the case of Brazilian hydropower system

ABSTRACT Reservoirs considerably affect river streamflow and need to be accurately represented in environmental impact studies. Modeling reservoir outflow represents a challenge to hydrological studies since reservoir operations vary with flood risk, economic and demand aspects. The Brazilian Interconnected Energy System (SIN) is an example of a unique and complex system of coordinated operation composed by more than 160 large reservoirs. We proposed and evaluated an integrated approach to simulate daily outflows from most of the SIN reservoirs (138) using an Artificial Neural Network (ANN) model, distinguishing run-of-the-river and storage reservoirs and testing cases whether outflow and level data were available as input. Also, we investigated the influence of the proposed input features (14) on the simulated outflow, related to reservoir water balance, seasonality, and demand. As a result, we verified that the outputs of the ANN model were mainly influenced by local water balance variables, such as the reservoir inflow of the present day and outflow of the day before. However, other features such as the water level of 4 large reservoirs that represent different regions of the country, which infers about hydropower demand through water availability, seemed to influence to some extent reservoirs outflow estimates. This result indicates advantages in using an integrated approach rather than looking at each reservoir individually. In terms of data availability, it was tested scenarios with (WITH_Qout) and without (NO_Qout and SIM_Qout) observed outflow and water level as input features to the ANN model. The NO_Qout model is trained without outflow and water level while the SIM_Qout model is trained with all input features, but it is fed with simulated outflows and water levels rather than observations. These 3 ANN models were compared with two simple benchmarks: outflow is equal to the outflow of the day before (STEADY) and the outflow is equal to the inflow of the same day (INFLOW). For run-of-the-river reservoirs, an ANN model is not necessary as outflow is virtually equal to inflow. For storage reservoirs, the ANN estimates reached median Nash-Sutcliffe efficiencies (NSE) of 0.91, 0.77 and 0.68 for WITH_, NO_ and SIM_Qout respectively, compared to a median NSE of 0.81 and 0.29 for the STEADY and INFLOW benchmarks respectively. In conclusion, the ANN models presented satisfactory performances: when outflow observations are available, WITH_Qout model outperforms STEADY; otherwise, NO_Qout and SIM_Qout models outperform INFLOW.

Hydroelectricity water footprint in Parana Hydrograph Region, Brazil

Abstract Brazil depends on hydroelectricity. Recently, concerns related to the water consumption by the hydropower plants (HPs) are increasing, mainly because of the severe droughts that have affected Parana Hydrograph Region (PHR). PHR accounts for more than 60% of the hydroelectricity produced in the country, being one of the most important in the world. This study aimed to evaluate Gross and Net Water Footprints (GWF and NWF) in 67 HPs installed in PHR that are belong to the Brazilian interconnected power generation and transmission system (SIN), focusing on a regional analyzes approach. We could observe that HPs with reservoirs for streamflow regularization presented the highest values of WF. HPs with a lake at a constant level (run-of-river scheme) showed the lowest WF values. A significant relationship between GWF and NWF and flooded area/installed power ratio (A/P) could be assessed by analyzing the HPs individually as well as in the basins. On average, NWF corresponded to 44.6% of the GWF, being below the average that has been estimated around the world. GWF and NWF of the hydroelectricity in PHR between 2002 and 2016 were, respectively, 25 and 11 m3 GJ−1, both lower than values estimated for other plants and regions in the world.

Power Systems Protection Course in the Electrical Engineering Programs Offered in Brazil

This paper presents a study of the Power Systems Protection (PSP) course in the Electrical Engineering programs offered in Brazil. The course offered to the undergraduate students has great importance for the future professional of Power System Engineering and should consider aspects to ensure that the future professionals have the necessary skills to carry out the craft of the profession. Initially, the importance of the PSP theme is presented through a compilation of local data (Brazil) regarding the Brazilian Interconnected Electrical System and its impacts on the operation and issues as failures and accidents. The article continues briefly describing the Electrical Engineering programs in Brazil, with current and historical data on Engineering and specifically Electrical Engineering, comparing them with other programs. The official number of Electrical Engineering programs of public and private educational institutions in Brazil and the number of programs that the course is mandatory or optional is also compared. Following, it is presented the characteristics and common subjects addressed in the course syllabus in the different best Brazilian educational institutions according to the Brazilian Institute of Studies and Research (INEP). Finally, the paper is concluded presenting a discussion about the necessity of maintain, increase or decrease the offer of this particular course and the necessity of update its syllabus.

Tracking Power System State Evolution with Maximum-correntropy-based Extended Kalman Filter

This paper develops a novel approach to track power system state evolution based on the maximum correntropy criterion, due to its robustness against non-Gaussian errors. It includes the temporal aspects on the estimation process within a maximum-correntropy-based extended Kalman filter (MCEKF), which is able to deal with both nonlinear supervisory control and data acquisition (SCADA) and phasor measurement unit (PMU) measurement models. By representing the behavior of the state variables with a nonparametric model within the kernel density estimation, it is possible to include abrupt state transitions as part of the process noise with non-Gaussian characteristics. Also, a novel strategy to update the size of Parzen windows in the kernel estimation is proposed to suppress the effects of suspect samples. By properly adjusting the kernel bandwidth, the proposed MCEKF keeps its accuracy during sudden load changes and contingencies, or in the presence of bad data. Simulations with IEEE test systems and the Brazilian interconnected system are carried out. The results show that the method deals with non-Gaussian noises in both the process and measurement, and provides accurate estimates of the system state under normal and abnormal conditions.

Study and Simulation of Voltage Profile Recovery on a 200 km Transmission Line Using Shunt Static Var Compensator (SVC)

This article aims to clarify how Flexible Alternating Current Transmission Systems (FACTS) technology, for static operating devices, conditioned on application to long-distance transmission lines can solve problems related to voltage drop on paths known as “weak zones” of the power transmission system. Some technical aspects of the construction of the SVC Static Reactive Compensator in conjunction with thyristor switching devices such as TCR and TSC are described. The proposed scenario is similar to the Brazilian interconnected system, where much of the generator park is hundreds of miles from the country's major consumer centers, leading to the structure of this system longer transmission lines and consequently greater losses in the transmission paths. For the proposed simulations the MATLAB Simulink ® environment was used considering different voltage unbalance operating ranges caused by three-phase faults in the transmission lines. The conclusions show that the distance from the lines to the load has a great influence on the oscillatory effects of voltage, and the fact that the “loading” transmission lines can compensate for much of the path by generating wars through the circuit's natural capacitance. The allocation of capacitor and shunt reactor banks is a reliable option for the transmission system and can act as a support mechanism for voltage control maneuvers to circumvent abrupt changes in reactive demand. From the simulations output comparison, the transient effects showed greater stability in the voltage signal recovery in the stretches where the compensation blocks were located near the lowering substation bus, thus demonstrating the capacity of the applied technology.

Fuzzy PID Controller Design for LFC in Electric Power Systems

In this paper, a methodology using Differential Evolution algorithm is proposed for the definition of the discourse universe of the fuzzy PID controller structure variables, for the load/frequency control in power systems, with this eliminating the need of the expert in systems speed control of hydraulic turbines. This controller uses the fuzzy system to tune the PID controller in real time. A mathematical model, based upon constructive information and where nonlinearities are taken into account, of a hydroelectric plant belonging to the Brazilian Interconnected System is presented as a test benchmark to analysis the proposed controller performance under various loading conditions. Simulation results are introduced to show the performance of the developed controller in comparison with a PID controller tuned by a Differential Evolution Algorithm and with a PID algorithm similar to the one actually used in the field. These results denote that the proposed controller offer better performance over others in terms of settling times and oscillation of the frequency.

Influence of Integration of Wind Power in Planning the Operation of a Hydrothermal System Using Dynamic Systems

This paper presents a model that aims to understand the operation of a hydrothermal system using System Dynamics technique for this uses as basis the Brazilian Interconnected System. From the developed modeling is possible to obtain, in view of the decision to use water of the reservoirs in the present or save for the future, the consequences of this decision in the short term price of the energy (Spot Price). Moreover, it is also realized an analysis of the impact of different forms of integration of wind generation in the order of energy as well as some tests with possible scenarios of Energy Natural Affluent.

Technical-economic analysis for the integration of PV systems in Brazil considering policy and regulatory issues

The increasing integration of distributed renewable energy sources, such as photovoltaic (PV) systems, requires adequate regulatory schemes in order to reach economic sustainability. Incentives such as Feed-in Tariffs and Net Metering are seen as key policies to achieve this objective. While the Feed-in Tariff scheme has been widely applied in the past, it has now become less justified mainly due to the sharp decline of the PV system costs. Consequently, the Net Metering scheme is being adopted in several countries, such as Brazil, where it has is in force since 2012. In this context, this paper aims to estimate the minimum monthly residential demand for prosumers located in the different distribution concession areas in the interconnected Brazilian system that ensures the economic viability of the installation of PV systems. In addition, the potential penetration of PV-based distributed generation (DG) in residential buildings is also estimated. This study was conducted for the entire Brazilian interconnected system and it demonstrates that the integration of distributed PV systems is technical-economic feasible in several regions of the country reinforcing the role of the distributed solar energy in the diversification of Brazilian electricity matrix.

Políticas públicas coordenadas e presidencialismo de coalizão: o caso do PROMESO

Resumo As políticas públicas têm sido estudadas com base em diferentes aspectos teóricos. No entanto, ainda persiste uma lacuna nas questões relacionadas à integração de ações das agências governamentais. Essas dimensões, quando estudadas, pouco se aproximam da perspectiva dos impactos decorrentes da arquitetura do presidencialismo de coalizão sobre as políticas públicas, que, no caso brasileiro, corrobora sua fragmentação e competição entre agências governamentais que deveriam atuar de forma integrada. Este artigo objetiva identificar onde esse problema se manifesta e o ponto de inflexão entre o discurso da ação coordenada e a implementação que evidencia o contrário. Para demonstrar como isso ocorre foi escolhido o Programa de Promoção da Sustentabilidade de Espaços Sub-Regionais (Promeso), que tem agendas compartilhadas como um de seus importantes instrumentos. A elaboração da pesquisa demandou uma revisão teórica que se debruçou sobre a arquitetura institucional do presidencialismo de coalizão e dos partidos políticos, além de adotar, na pesquisa empírica, a base de dados da Secretaria de Orçamento Federal (SOF/MPOG) e do Sistema Integrado de Administração Financeira do Governo (Siafi/MF), que permitiram espacializar a distribuição dos recursos públicos segundo as lógicas partidárias e regionalizadas, e consultar documentos oficiais do Ministério da Integração Nacional (MI) que caracterizam o programa objeto deste estudo. A pesquisa comprovou que o presidencialismo de coalizão afeta diretamente as políticas públicas, evidenciando um caráter competitivo entre as agências do governo federal, em razão das lógicas particularizadas, determinadas pelos dirigentes dessas instituições.

Energization simulations of a half-wavelength transmission line when subject to three-phase faults—Application to a field test situation

The purpose of this paper is to supply technical data for the proposed field energization of 500kV transmission lines present in the Brazilian interconnected system, forming a line, henceforth called AC-Link, slightly over a half-wavelength in 60Hz. The purpose of the test is to investigate overvoltages and currents that result from the energization of the AC-Link. This paper shows the results of simulations performed in ATP (Alternative Transients Program) when considering the occurrence of three-phase faults along the AC-Link during energization. The results obtained show that, in certain situations, the overvoltages and energies in the arresters may reach very high values and some specific mitigation procedure should be implemented.

The Carbon Market Incremental Payoff in Renewable Electricity Generation Projects in Brazil: A Real Options Approach

The objective of this work is to present a methodology capable of estimating the incremental payoff of the carbon market for grid-connected renewable power generation projects in Brazil. The proposed methodology consists of using the NEWAVE model to determine the optimal operating policy for the Brazilian Interconnected System over the medium-term, and to establish hydrological dispatch scenarios for the power plants connected to this system. Based on these results, the criteria defined in the methodology ACM0002 were used to estimate the baseline of the projects developed in response to the Clean Development Mechanism of the Kyoto Protocol. Having estimated the baseline for the project, the incremental payoff obtained from the sale of Certified Emission Reductions is estimated using the real options theory. Subsequently, the value of the option is added to the conventional cash flow of the project, determining the impact of the carbon market on its internal rate of return.

Reliability Assessment of the Brazilian Power System Using Enumeration and Monte Carlo

Two methods have been largely studied and used in power systems reliability assessment: contingency enumeration and nonsequential Monte Carlo simulation. Both have their advantages and drawbacks. Contingency enumeration is conceptually simple and usually requires low computational effort. Conversely, Monte Carlo simulation is computationally harder, but much more versatile to model random aspects. This paper depicts some important practical aspects regarding the application of both methods, emphasizing how they can be used in a complementary way. The Brazilian interconnected electrical system is used to illustrate the risk assessment of an actual large scale power system, utilizing both techniques.

A large scale of an optimal deterministic hydrothermal scheduling algorithm

An application of a deterministic optimization algorithm in the hydrothermal scheduling of the large-scale Brazilian south-southeast interconnected system, composed of 51 hydro and 12 thermal plants and corresponding to 45 GW of installed capacity, is presented. The application considers the system operational conditions according to the 1986 Operational Plan coordinated by ELETROBRAS, the Brazilian electric holding company. The algorithm is based on a network flow approach especially developed for hydrothermal scheduling. For the south-southeast interconnected system, the problem formulation suggests a primal decomposition optimization approach. Two applications have been performed: in a study context, the system has been evaluated for the most critical stream flow ever recorded; in an operational context, the system has been simulated through an adaptive operational planning approach. The results show that the algorithm can be a useful tool for large-scale hydrothermal systems, giving insight into operational characteristics and/or adding to the guidance of real system operation. >

Operation Planning Studies of the Brazilian Generating System

This work outlines the methodology currently used for energy operatlon planning studies of the Brazilian interconnected system. These studies involve the use of different models in a chain of procedures, which has the overall objective of achieving the most rational utilization of the available resources. Some characteristics of the Brazilian hydrothermal system are presented, It is a Multi-owned system, significantly dependent on hydro generation, with a large number of plants and reservoirs arranged in a complex topology. A description of the institutional structure of the Brazilian power sector is also presented.