Carlos Mateo

Reference Network Models: A Computational Tool for Planning and Designing Large-Scale Smart Electricity Distribution Grids

Reference Network Models (RNMs) are large-scale distribution network planning tools. RNMs can be used by policy makers and regulators to estimate efficient distribution costs. This is a very challenging task, particularly being network planning a combinatorial problem, which is especially difficult to solve due to the vast size of the distribution areas, and the use of several voltage levels. This chapter presents the main features of RNMs developed by the authors, including high performance requirements related to the type and size of the problem. The model can be used to plan distribution networks either from scratch or incrementally from existing grids. Different case studies illustrate the applicability of these models to the assessment of the impact of massive deployment of renewable distributed generation, demand response actions, and plug-in electric vehicle penetration on distribution costs. The results obtained provide valuable information to guide strategic policy-making decisions regarding the implementation of renewable energy programs and smart grid initiatives.

Assessing the impact of distributed generation on distribution network costs

The support of electricity generation from renewable energy sources (RES) and combined heat and power (CHP) has led to increasing penetration levels of distributed generation (DG). Nevertheless, Large-scale connection of DG faces numerous regulatory, economic, social and technological challenges. Distribution networks were not originally designed to accommodate generation. Hence, distribution system operators (DSOs) face great uncertainties about the impacts of DG on distribution network planning and operation. This paper presents a quantification of how DG affects distribution network costs in three real distribution areas. Several scenarios of demand and DG have been analysed for each case study. Two reference network models (RNMs) have been used to consider the most critical snapshots within each scenario: maximum demand-minimum generation and maximum generation-minimum demand. Results yielded significant differences among the three case studies.

Optimal degree of smart transformer substations in distribution networks for reliability improvement

The medium to low voltage transformer substation is a key element in the distribution system. Therefore, smart transformer substations will play a crucial role in the evolution of distribution towards the smart grid. Smart transformer substations can provide a significant improvement of continuity of supply. However, a large investment is required, so the optimal degree of automation must be determined. The main objective of this paper is to quantify the impact of smart MV/LV transformer substations on continuity of supply, which is essential to determine the optimal automation degree. The analysis has considered different degrees of implementation of smart MV/LV substations for different configuration schemes of urban distribution networks. Furthermore, sensitivity analyses have been performed for the main parameters involved so that conclusions on reliability improvement achieved by MV/LV transformer substation automation can be scaled up.

Mitigating the impact of distributed generation on distribution network costs through advanced response options

Nowadays, the presence of distributed generation (DG) is steadily growing. This growth can produce significant effects on the costs incurred by distribution system operators (DSOs). This impact can be particularly negative if DG keeps playing a passive role, not reacting to network conditions. However, the implementation of advanced response options or active network management (ANM) may mitigate the adverse effects of large DG penetration levels. This paper considers the adoption of ANM planning strategies and provides an estimate of the distribution network costs reduction that can be achieved through the implementation of advanced response options. Two large-scale distribution planning models, called reference network models (RNMs), have been used to calculate these cost estimates. Three actual distribution areas are studied, taking into account different scenarios of load and DG for each one of them. These areas are located in The Netherlands, Germany and Spain and were chosen to reflect a wide range of different types of consumers, load concentration and DG technologies.

Elastic Guided Wave Propagation in Electrical Cables

This article analyzes the propagation modes of ultrasound waves inside an electrical cable in order to assess its behavior as an acoustic transmission channel. A theoretical model for propagation of elastic waves in electric power cables is presented. The power cables are represented as viscoelastic-layered cylindrical structures with a copper core and a dielectric cover. The model equations then have been applied and numerically resolved for this and other known structures such as solid and hollow cylinders. The results are compared with available data from other models. Several experimental measures were carried out and were compared with results from the numerical simulations. Experimental and simulated results showed a significant difference between elastic wave attenuation inside standard versus bare, low-voltage power cables.

Short-Time Fourier Transform with the Window Size Fixed in the Frequency Domain

Abstract The Short-Time Fourier Transform (STFT) is widely used to convert signals from the time domain into a time–frequency representation. This representation has well-known limitations regarding time–frequency resolution. In this paper we use the basic concept of the Short-Time Fourier Transform, but fix the window size in the frequency domain instead of in the time domain. This approach is simpler than similar existing methods, such as adaptive STFT and multi-resolution STFT, and in particular it requires neither the band-pass filter banks of multi-resolution techniques, nor the evaluation of local signal characteristics of adaptive techniques. Three case studies are analyzed and the results show that the proposed method allows better identification of signal components compared to standard STFT, multi-resolution STFT and Adaptive Optimal-Kernel Time Frequency Representation, although the method is not computationally efficient in its present form. Some synthetic and real world signals are used to demonstrate the effectiveness of the proposed technique.

Development of a current sensor based on active materials for high-voltage transmission systems

This paper presents the development of a new class of current sensor based on active materials for high-voltage transmission systems. This current sensor is an innovative design with respect to conventional current measurement transformers. The alternating current signal to be measured induces a magnetic field in an emitter which consists of a magnetostrictive material. The emitter transforms the current magnetic energy into mechanical energy in the form of mechanical waves due to the alternating nature of the induced magnetic field. These waves are transmitted through a dielectric structure until a piezoelectric stack, the receiver, is reached which converts the mechanical energy back into electrical energy. An electronic signal module processes this low electrical current and estimates the primary current to be measured. A numerical model has been developed to evaluate the preliminary design. A small scale prototype has been built and tested to demonstrate the feasibility of the current sensor. Experimental data have been used to fit the damping parameters of the model.

Replicability Analysis of PLC PRIME Networks for Smart Metering Applications

Advanced metering infrastructures (AMIs) represent one of the first steps in the smart grid process, where power line communication (PLC) is emerging as the most cost-effective solution since it allows reusing electric infrastructures as communication channel. However, the performance of this technology is highly affected by the characteristics of the existing distribution network. This paper presents a thorough sensitivity analysis to assess the operating limits of smart metering applications for multiple representative configurations of low voltage networks based on a PLC simulation framework that integrates DLMS/COSEM and PRIME standards. The number of registered nodes and the time to read all meters have been defined as key performance indicators to assess the communication performance. The conclusions drawn from this paper provide useful information for the integration of smart meter applications that take advantage of AMI under different local conditions.

Power line communication transfer function computation in real network configurations for performance analysis applications

Despite power line communication is considered a cost-effective solution to communicate electronic devices across the power system, the performance of this technology is highly affected by physical channel factors such as the presence of noise and signal attenuation. Such phenomena are mainly determined by the characteristics of the electrical infrastructure as well as by the network topology. This study presents an analytical approach to systematically compute the signal attenuation between any pair of nodes in real electric power distribution network topologies based on transmission-line theory and graph theory. The proposed methodology has been applied to obtain the attenuation matrix of two representative networks for low and medium voltage. In addition, the results have been used to analyse the communication performance of these networks, where the low voltage network shows better results due to the reduced number of nodes and network length. The conclusions of this study motivate the application of this methodology to power line communication networks planning.

Replicability analysis of PLC PRIME networks for smart metering applications

Advanced Metering Infrastructures (AMI) represent one of the first steps in the Smart Grid process, where Power Line Communication (PLC) is emerging as the most costeffective solution since it allows reusing electric infrastructures as communication channel. However, the performance of this technology is highly affected by the characteristics of the existing distribution network. This article presents a thorough sensitivity analysis to assess the operating limits of smart metering applications for multiple representative configurations of low voltage (LV) networks based on a PLC simulation framework that integrates DLMS/COSEM and PRIME standards. The number of registered nodes and the time to read all meters have been defined as Key Performance Indicators to assess the communication performance. The conclusions drawn from this study provide useful information for the integration of smart meter applications that take advantage of AMI under different local conditions.