Power quality studies for distribution networks are very important for future network expansions realized by utility companies, so the accuracy of such studies is critical. Load data, including information on load imbalance, could have in many situations a significant influence on the correct estimation of many power quality indicators. This paper investigates the impact of load imbalance on several phase imbalance indicators and voltage quality indicators by comparing the values of these indicators, as calculated in a power quality study using, sequentially, different sets of load data characterized by different load imbalances. The results of this study confirm the original hypothesis, showing that the use of inaccurate consumption profiles for loads leads to an inaccurate estimation of some power quality indicators. In addition, the results highlight the difficulty of approximating the actual consumption profiles of electrical loads so that this approximation does not affect the correctness of the estimation of phase imbalance and voltage quality indicators.

Future distribution grids will be subjected to fluctuations in voltages and power flows due to the presence of renewable sources with intermittent power generation. The advanced smart metering infrastructure (AMI) enables the distribution system operators (DSOs) to measure and analyze electrical quantities such as voltages, currents and power at each customer connection point. Various smart grid applications can make use of the AMI data either in offline or close to real-time mode to assess the grid voltage conditions and estimate losses in the lines/cables. The outputs of these applications can enable DSOs to take corrective action and make a proper plan for grid upgrades. In this paper, the process of development and deployment of applications for improving the observability of distributions grids is described, which consists of the novel deployment framework that encompasses the proposition of data collection, communication to the servers, data storage, and data visualization. This paper discussed the development of two observability applications for grid monitoring and loss calculation, their validation in a laboratory setup, and their field deployment. A representative distribution grid in Denmark is chosen for the study using an OPAL-RT real-time simulator. The results of the experimental studies show that the proposed applications have high accuracy in estimating grid voltage magnitudes and active energy losses. Further, the field deployment of the applications prove that DSOs can gain insightful information about their grids and use them for planning purposes.

The expected growth in distributed generation will significantly affect the operation and control of today's distribution grids. Being confronted with fast fluctuating power from distributed generations, the assurance of a reliable service (grid stability, avoidance of energy losses) and the quality of the power may become costly. In this light, Smart Grids may provide an answer towards a more active and efficient electrical network. The EU project SmartC2Net aims to enable smart grid operations over imperfect, heterogeneous general purpose networks, which poses a significant challenge to the reliability due to the stochastic behaviour found in such networks. Therefore, key concepts are presented in this paper targeting the support of proper smart grid control in these network environments and its Real-Time Hardware-In-the Loop (HIL) verification. An overview on the required Information and Communication Technology (ICT) architecture and its functionality is provided and a description of a relevant use case that deals with voltage control on medium and low voltage networks along its evaluation approach on an experimental test bed is detailed.

In some situations, the symmetrical components of voltage and current are more sensitive to electric faults compared to their phase-domain counterparts. For this reason, several protection relays operate on symmetrical components and many protection engineers continue to develop protection algorithms that rely on these quantities. This paper reviews the literature on the use of symmetrical components in electrical protection and sorts it in categories covering line protection, generator/motor protection, transformer protection and protection of distribution networks and microgrids. The review shows that symmetrical components are used by over-current/-voltage elements, distance relaying, directional algorithms, differential schemes, adaptive protection and protection algorithms based on relationships of symmetrical components. This paper also presents, in short, the theoretical background of symmetrical components and their derivation from the phase-domain quantities.

One of the main issues concerning large penetration of the renewable energy based generators on the distribution network is related to the voltage variations due to intermittent character of the solar irradiance and wind. The actual power quality standards provide only general information regarding the evaluation procedure of the voltage fluctuations and no directions regarding the sampling frequency of the data used. As a consequence, most of the studies neglect effect of the solar irradiance and wind speed in fast changing conditions on the utility grid. This work proposes a methodology to evaluate the voltage fluctuations into the low voltage distribution network caused by variable generation and reveals the influence of data resolution on the final results. A short review regarding the assessment of the voltage variations is presented in advance and an appropriate model of the power system is build, including the generating units that are capable to operate with high resolution input data. Real parameters for the components of the simulated system are used in order to obtain realistic results.

The method of symmetrical components simplifies analysis of an electric circuit during the fault and represents an important tool for the protection engineers. In this paper, the symmetrical components of the fault current are used in a new feeder protection method for the maritime applications. The new method is effective against the phase-phase fault and relies on evaluation of the ratio of negative-sequence to positive-sequence current to detect such faults. It is shown that the proposed ratio is a complex number and its magnitude is associated with the presence of the phase-phase fault in a radial feeder, while its argument is an indicator of the fault direction. Precisely these information are used in this paper to detect the phase-phase fault and to indicate the faulted section of the feeder. Using PSCAD, the new method is implemented in a test Medium Voltage feeder with variable generation and relatively reduced short-circuit currents, thus resembling the electric network on a ship. The simulation results demonstrate that the proposed method of protection provides an improved performance compared to the conventional OverCurrent relays in a radial feeder with variable short-circuit power.