Brazilian Transmission Research Articles

Case Studies of Battery Energy Storage System Applications in the Brazilian Transmission System

This paper presents the preliminary results of studies aiming to use a battery energy storage system (BESS) in the Brazilian transmission system. The main objective of the BESS is to solve congestion problems caused mainly by the large increase in variable renewable generation in certain system areas. The studies were conducted based on actual forecasted system scenarios using a full representation of the electric grid available from the Brazilian system operator data base. In this work, only the steady-state modeling was considered as this may be the first stage in the assessment of a new technology. A qualitative economic comparison of the BESS application with other possible solutions to the congestion problems is also included.

Quality analysis of the defect location information in transmission line outages caused by fires

<span lang="EN-US">This paper analyzed the quality of the information regarding power outages caused by fires in the Brazilian transmission system in the years 2018 and 2019. Six transmission line trunks with asymmetrical performance regarding fire-related outages in the period were selected. The selected trunks correspond to twelve 500 kV transmission lines with a total length of 3,998 km. Outage, geospatial transmission line data and fire outbreak information was compared for twelve transmission lines of interest, all located in regions with a high incidence of fires. The results suggest that the data provided by the transmission line fault locating equipment is not accurate when compared to the fire outbreak data provided by satellites.</span>

Impact of the specific fire load on the performance of power transmission lines

Transmission line outages caused by fires are frequent and affect the electric power supply to the population. Studying the factors that may aid in the understanding of this problem is fundamental to improve performance and guide future projects involving this type of installation. This study analyzed the forest inventories of vegetation adjacent to three Brazilian transmission line trunks and calculated their specific fire loads. The results were compared with the performance of these installations and revealed a high correlation (R2=0.9877) between the fire load and the number of transmission line outages, demonstrating the influence of vegetation on the operation of these installations.

Toward a New Nodal Pricing Policy of the Brazilian Transmission System Considering Multiple Hydrological Scenarios

This paper presents a new method for allocating transmission system costs in hydro prevailing energy markets. The proposed approach is based on nodal pricing, and it considers multiple hydrological scenarios obtained from optimized energy models. These models are much closer to the operational reality of hydro dominant systems and more adequate to the transmission operation planning. The nodal pricing strategy comprises two steps to recover the total costs of the transmission system. The first one calculates the charges corresponding to the utilized network capacity, estimated at a specified operating condition, and it brings the locational signal to the tariff. In the second step, the charges related to the transmission capacity available but not used in the system are assessed by a postage stamp. This latter step accomplishes the task of recovering the total transmission charges and defining the final tariff for specific operating dispatching. On the other hand, the optimized energy models, based on stochastic dual dynamic programming, are used to minimize the operating costs while penalizing possible energy spillages. These models create monthly sequences of hydrothermal coordinated generating scenarios and dispatching conditions, which are used by the nodal pricing strategy to produce the generation/load charges and tariffs and the corresponding statistics. The proposed method, combining the nodal pricing strategy and the optimized energy model, is applied to a Brazilian network configuration and the results are fully discussed. Moreover, probabilistic analyses are also performed to describe the annual costs of transmission of thermoelectric and hydroelectric plants and industrial electrointensive consumers installed in different areas of the network.

Discussion on the Interaction between Transformers and the Power Systems

A general increase in transformer dielectric failures in the Brazilian transmission system, some of them with no specific causes, motivated the start up of a Cigré Joint Working Group JWG A2/C4–03 Electrical Transient Interaction between Transformers and the Power System. This group has been gathered to assess and discuss the different types of electrical transient interaction between transformers and other components of the T&D power system that could explain some of these failures. The main focus of the JWG is to pursue an improvement of the system reliability based on recommendations regarding the electrical transient interaction between transformers and the power system. This takes into account the necessity of detailed transient studies looking for an upgrade in equipment specifications, system planning and operation criteria. The working group started its activities in May 2005 and is composed of around 30 members, representing utilities, research center, manufacturers, universities and the national grid system operator. The objective of this paper is to present the work that has been carried out so far by the JWG including the main discussions and the conclusions already reached.

A Goal-Oriented Approach for Supporting Input/Output Determinationin Regulatory Benchmarking of Brazilian Electricity Transmission

A Goal-Oriented Approach for Supporting Input/Output Determinationin Regulatory Benchmarking of Brazilian Electricity Transmission

A Holistic Methodology to Identify Cost-Effective Smooth Routes for Power Transmission Lines

The design of cost-effective power line routes is a critical step towards elaborating a consistent network expansion plan. Although several attributes are considered by planning agents, the impact of sharp curvatures is typically neglected within the route design process, thus not accounting for the need for more expensive structures to support the power line. In this work, we tackle this issue by developing a holistic methodology that combines geoprocessing technologies with a novel combinatorial optimization technique to assist practitioners in identifying cost-effective smooth power line routes. For the latter, since the fundamental mathematical structure of the proposed tool falls into the class of a Quadratic Shortest Path Problem, an efficient dynamic programming algorithm is designed to handle the typical large-scale instances of power line tracing applications. The effectiveness of the proposed methodology is illustrated with a case study based on a real-world project of the Brazilian transmission sector.

Time-domain distance protection of transmission lines based on the conic section general equation

This paper presents the development, implementation, and testing of a time-domain distance protection algorithm based on the behavior of voltage and current signals over time and on the conic section general equation that describes this behavior. The authors used six existing electrical systems modeled in ATP/EMTP to perform fault simulations varying the fault type, phases involved, fault resistance, inception angle, and fault location. Besides, the authors carried out a sensitivity analysis regarding the sampling frequency influence, noisy data, dynamic behavior of capacitor voltage transformers, power swings, and close-in faults. Finally, the authors tested the proposed method against an actual fault event on a 500 kV Brazilian transmission line. The results presented in this paper indicate that the proposed solution is robust, fast, accurate, secure, and dependable.

Accounting multiple environmental variables in DEA energy transmission benchmarking modelling: The 2019 Brazilian case

The non-parametric Data Envelopment Analysis (DEA) benchmarking method is frequently used by regulators to compare companies under natural monopolies. The Brazilian Energy regulator uses such an approach to define the efficient operational costs of the transmission companies. In 2019, a second-stage procedure was applied to include the effects of environmental variables on operational cost efficiency. However, only a few environmental variables were used to estimate efficient costs. This study proposes a new methodology for adjusting cost efficiencies using multiple contextual variables. Our proposal aims to adjust the input variable, using different environmental variables, before estimating the cost efficiencies. Therefore, multiple cost efficiencies are estimated, one for each environmental variable. Our proposal is based on the linear regression Analysis-of-Variance property. Results indicate that due to environmental heterogeneity of Brazilian transmission companies, cost efficiencies adjusted using multiple environmental variables are of utmost importance. Thus, our proposal manages to successfully include multiple environmental variables in the model, generating fair adjustments in the efficiency scores, and avoiding the effects of DEA modeling biases that are common in second-stage analyses.

Analysis of the impacts on the Brazilian transmission infrastructure due to the decrease in imports of natural gas from Bolivia

Analysis of the impacts on the Brazilian transmission infrastructure due to the decrease in imports of natural gas from Bolivia

Benchmarking the operational expenditures of Brazilian transmission utilities by using DEA models

In Brazil, the transmission assets are remunerated for their availability regardless of the full utilization of their capacities. The annual allowed revenue for each transmission utility is determined by the Brazilian Electricity Regulatory Agency (ANEEL). ANEEL has been using Data Envelopment Analysis (DEA) to define the regulatory operational expenditure (OPEX) for each utility, a key element for the annual allowed revenue assessment. Based on the ANEEL's DEA model this work proposes improvements in representing the quality of service, transmission capacity and transmission network length in the DEA model. Furthermore, this paper presents a more robust methodology to evaluate the regulatory operational expenditure of transmission utilities by applying several distinct DEA models; then a global efficiency score is defined by the geometric mean of the efficiency scores resulting from the set of DEA models analyzed. The performance of the proposed approach is illustrated with real data of the Brazilian transmission utilities.

Transformer Fleet Optimal Maintenance with Risk Considerations

This paper aims at proposing an optimization model for high voltage transformers’ maintenance scheduling to minimize operational cost and risk. The focus of the paper is on the transformer fleet management, and not on a single transformer maintenance procedure or the evaluation of a single transformer failure risk. The proposed methodology takes as inputs the importance (e.g., based on the expected energy not supplied) and failure risk of each transformer (e.g., based on on-line Dissolved Gas Analysis), and the maintenance cost for each transformer. It also considers the main practical constraints in field interventions. As output, the proposed methodology provides the best timing for the maintenance of each transformer from the fleet of interest. The problem has been modeled as mixed-integer linear programming. Eleven months of real data from the Brazilian transmission system are used for setting up the recent history of outages. The following year data are employed to test the effectiveness of the optimization model. The output of the proposed fleet maintenance scheduling tool is the optimum viable intervention calendar for a power transformer fleet within a 52-week horizon. This proposal represents an innovative and robust solution, which can support the operational planning experts’ decision-making process.

Performance benchmarking models for electricity transmission regulation: Caveats concerning the Brazilian case

Regulation plays an important role under natural monopoly markets, such as energy electricity distribution and transmission. In recent years, abrupt changes in the regulation of the Brazilian Transmission System Operators (TSOs) has increased the risk perceived by investors, harming the economic stability of the sector. In this paper, we present a review of the benchmarking model used to regulate Brazilian TSOs' operational costs. The objective of the paper is to suggest improvements in the Data Envelopment Analysis (DEA) model proposed by the regulator in 2018. The suggested changes would help to ensure a robust and reliable regulatory process.

HVDC multi-infeed analysis of the Brazilian transmission system and possible mitigation methods

The Brazilian transmission system is facing challenging problems with the distance between its generation areas and consumer centers that will be partly solved by the use of HVDC point-to-point systems. In the near future, the southeast subsystem will have a large amount of power injected through HVDC Systems in multiple points with relatively close electrical proximity. Therefore, the effects of a multi-infeed system are expected to influence the performance and operation of the network. Extensive studies and simulations will play an important role in determining the extension of the interactions among HVDC converters and determine if such interactions cause multiple commutation failures, thus disturbing the dynamic stability of the system. The use of CCC (Capacitor Commutated Converter) HVDC systems will also be assessed and is expected to diminish the need for a strong AC network (high short circuit level) and, therefore, mitigate multi-infeed interactions. The southeast subsystem of the Brazilian Power System currently has four LCC inverters, two of them belong to the Madeira power plant and the other two are from the Itaipu power plant. By the year 2024, four other HVDC systems will be arriving in the same region. This paper discusses the HVDC multi-infeed phenomena regarding the relevance of using synchronous machine models to represent important power plants and the application of mitigation methods regarding the 2020 network model, where six HVDC links will be present.

An algorithm for cost optimization of PMU and communication infrastructure in WAMS

Power system state estimation relies increasingly on PMU measurements to effectively control and monitor growing and stressed transmission networks which are also affected by transient and dynamic events. High PMU cost has motivated optimal PMU placement solutions but recent works have shown the effect of communication infrastructure cost in PMU configuration. In this paper, we present a new method for the design of Wide Area Measurement Systems. A topological analysis algorithm based on the Variable Neighbourhood Search heuristic is proposed and tested in several networks, including the common IEEE test networks and the 5804-bus Brazilian transmission system. Our results show the flexibility, effectiveness, and scalability of the proposed methodology when compared with recent research presented in the literature.

Numerical modeling of geomagnetically induced currents in a Brazilian transmission line

Rapid changes in the external geomagnetic field induce electric currents in conducting materials at the Earth’s surface. These geomagnetically induced currents (GIC) are mostly studied in transmission lines at high-latitude due to their frequent hazards. However, recent studies have shown that low- and middle-latitude regions may also be subject to problems due to GIC occurrences. In this work we apply a numerical model, using plane wave theory and a one-dimensional electrical resistivity model of the region, to calculate the geoelectric field and the GIC measured directly at the Itumbiara–São Simão (IS) transmission line (Southeast Brazil) during a magnetic storm occurred between 7–10th November 2004. We use two electrical resistivity models: (a) one-layer model, in which our results do not reproduce the measured GIC directly in the IS transmission line, and (b) four-layer model, which presents similar patterns of temporal variation and intensities of the measured electric fields and GIC. After validating the four-layer numerical model, we calculate the electric fields and GIC during the “Halloween storm” (29th October–1st November 2003). Our results of the Halloween storm show maximum GIC amplitudes of 25A, which are higher than registered in other middle latitude countries, such as South Africa and Uruguay. These results indicate that the Brazilian power network might be subjected to the GIC hazards in the future due to strong magnetic storms. In addition, our numerical model might be used as a potential tool for different geological sets, electrical resistivity models, transmission lines with distinct characteristics and for a range of magnetic storms intensities.

Electromagnetic Power Extraction of Transmission Lines

The main idea of this project is to feed small loads along the lines of the TBE - Brazilian Energy Transmission with retreat directly from power lines without any physical contact. This paper presents the system for extracting small powers of the transmission line through electromagnetic effects. Initially, the mathematical modeling of extraction is presented, to then show some aspects of construction and prototype control. Some results of laboratory tests of the prototype are presented with various operating situations analysis. This equipment was installed experimentally in one of the lines of TBE and the current results are shown in this paper.

A New Methodology for Cost Allocation of Transmission Systems in Interconnected Energy Markets

This paper presents a new methodology for allocating transmission system costs in single or interconnected energy markets. Initially, the proposed method allows the decomposition of the total transmission cost into two components: the first corresponds to the utilized network capacity, estimated at a specified operating condition, and the second refers to the transmission capacity available but not used in the system. A technique for decomposing nodal tariffs per subsystem guarantees the applicability of the method to interconnected markets. From the proposed procedure, it is possible to determine the responsibility of each participant (or group of participants) in the use of any specified set of transmission elements. The flexibility of this method allows the establishment of criteria based on economic and technical aspects for cost allocation of internal circuits of each subsystem, as well as of the tie elements between the subsystems. Important characteristics of the proposed methodology, such as transparency, impartiality, and flexibility, are analyzed and illustrated based on numerical applications with the IEEE Reliability Test System. Experience with the Brazilian transmission network is also discussed.

Temperature profile of progressive damaged overhead electrical conductors

The Brazilian transmission system is characterized by installations that average 20years of operation. Competitiveness of the energy sector, lack of resources for new investments and the aging of the system lead to the necessity of not only to reform but also to optimize it in order to face the increasing demand of the Brazilian energy market. The overhead electrical conductor is naturally the most important element on the transport of electrical energy and requires careful predictive and preventive maintenance programs. Therefore, it is of fundamental importance to predict the operational life of overhead electrical conductors using mathematical models so that their energy transport capacity can be optimized. However, it is necessary to validate such models by means of test programs so that their predictions can be trusted. One of the most important factors on the structural decay of overhead electrical conductors is the variation of the temperature profile in the event of the rupture of one or more of its Aluminum wires by fatigue or fretting. Therefore, models that include this temperature variation must be validated through test programs that can experimentally establish a mathematical relationship which considers effects such as contact resistance, material thermo-mechanical properties modification, annealing of the material and the presence of defects. The objective of this work is to evaluate the effect of progressive Aluminum wire rupture on the temperature profile of an ACSR (Aluminum Conductor Steel Reinforced) overhead electrical conductor, not only on the section of the damage but also along the length of the conductor. A test procedure was developed and performed to establish this effect. Results were compared to a mathematical model and showed that the temperature profile dependency of the increasing rupture of Aluminum wires is not linear and includes effects other than the cross section loss.

Efficient procedure to evaluate electromagnetic transients on three-phase transmission lines

This paper presents a hybrid way mixing time and frequency domain for transmission lines modelling. The proposed methodology handles steady fundamental signal mixed with fast and slow transients, including impulsive and oscillatory behaviour. A transmission line model is developed based on lumped elements representation and state-space techniques. The proposed methodology represents an easy and practical procedure to model a three-phase transmission line directly in time domain, without the explicit use of inverse transforms. The proposed methodology takes into account the frequency-dependent parameters of the line, considering the soil and skin effects. In order to include this effect in the state matrices, a fitting method is applied. Furthermore the accuracy of proposed the developed model is verified, in frequency domain, by a simple methodology based on line distributed parameters and transfer function related to the input/output signals of the lumped parameters representation. In addition, this article proposes the use of a fast and robust analytic integration procedure to solve the state equations, enabling transient and steady-state simulations. The results are compared with those obtained by the commercial software Microtran (EMTP), taking into account a three-phase transmission line, typical in the Brazilian transmission system.