Theoretical Study of Potential Manufacturing Insulation Defects in Medium–Voltage Traction Motors

Medium-voltage motors dedicated to the applications of traction operate in an environment with strong multi-physics constraints. Electrical insulation of these engines is a complex multi-layered impregnated system which requires a given number of steps during the manufacturing process. In the present study, we theoretically investigated the potential manufacturing insulation defects of traction motors in low frequency domain. The aim is to assess the theoretical ability of dielectric spectroscopy method for the detection of these defects and the extension of the method to others insulation systems. The theoretical study is based on numerical modelling and simulation achieved by using Comsol Multiphysics software. In our numerical modelling the properties of the main dielectric elementary materials are frequency–dependent. The identification of each potential defect is carried out by comparing its equivalent capacitance and dissipation loss spectra with the characteristics of insulation without defect. As the results, all artificial defects are identifiable with a specific relative deviation. The detection of all the defects analysed will need a measuring device with resolution of 0.4%. Keywords—AC electric motors, Capacitance, dielectric, dissipation factor, composite insulation, numerical modelling.

Assessing Feature Importance for Short-Term Prediction of Electricity Demand in Medium-Voltage Loads

The design of new monitoring systems for intelligent distribution networks often requires both real-time measurements and pseudomeasurements to be processed. The former are obtained from smart meters, phasor measurement units and smart electronic devices, whereas the latter are predicted using appropriate algorithms—with the typical objective of forecasting the behaviour of power loads and generators. However, depending on the technique used for data encoding, the attempt at making predictions over a period of several days may trigger problems related to the high number of features. To contrast this issue, feature importance analysis becomes a tool of primary importance. This article is aimed at illustrating a technique devised to investigate the importance of features on data deemed relevant for predicting the next hour demand of aggregated, medium-voltage electrical loads. The same technique allows us to inspect the hidden layers of multilayer perceptrons entrusted with making the predictions, since, ultimately, the content of any hidden layer can be seen as an alternative encoding of the input data. The possibility of inspecting hidden layers can give wide support to researchers in a number of relevant tasks, including the appraisal of the generalisation capability reached by a multilayer perceptron and the identification of neurons not relevant for the prediction task.

Differential Analysis of Fault Currents in a Power Distribution Feeder Using abc, αβ0, and dq0 Reference Frames

This paper proposes a methodology to monitor the instantaneous value of the current and its derivative in the abc, αβ0, and dq0 reference frames to act in the detection of fault current in medium-voltage distribution systems. The method employed to calculate the derivative was Euler’s, with processing sampling rates of 10, 50, 100, and 200 μs. Using the MATLAB/Simulink platform, fault situations were analyzed on a real feeder of approximately 1.1132 km in length, fed by an 11.4 kV source, composed of 26 unbalanced loads and modeled as constant power. The simulation results show that the detection occurred in the different fault situations implemented in the feeder and that the detection speed is related to the value of the processing sampling rate (PSR) used. Considering all fault situations and regardless of the PSR value used, the total average detection time was 49 µs. Besides that, the joint action of the detection system with the Thyristor Controlled Series Capacitor (TCSC) limited the fault current in each situation. The average detection time for each fault situation analyzed was below the typical time for a recloser to act, regardless of the reference adopted for the analysis.

The Role of Root Cause Analysis (RCA) in Power Distribution Network Interruption Reduction

Responsibility and reliability are very important for electricity subscribers. Due to their extent, these networks face a variety of challenges, and most of them are recurring but can be prevented if the root causes are identified. One of the methods to identify the root of network problems is to use the RCA method in the analysis of blackouts. RCA is an approach that systematically investigates adverse events and, by gathering evidence and documentation, finds its root causes and offers solutions to address them. Finally, it monitors the implementation of solutions and evaluates their effectiveness. In this chapter, while introducing some of the challenges of medium voltage power supply networks, the root of the problems are extracted, and corrective solutions are presented in three sample problematic feeders. After extracting the solutions, they are divided into two categories: the first category is the solutions specific to the sample feeder, and the second category is the solutions that can be generalized to other parts of the power supply network.

Loss of the Bird Diverter Efficiency at a Medium Voltage Overhead Power Line – Example of the Aktobe Region (Republic of Kazakhstan)

This report presents the results of survey of a 46-kilometer section of the overhead line (OHL) powering the cathodic protection of the Bukhara – Ural Gas Pipeline within the Aktobe Region of the Republic of Kazakhstan. 7 kilometers of this section were previously equipped with bird protection devices (BPDs), which are now totally lost due to destruction of their fastening elements. Inspection of the 46-km section of this OHL has revealed deaths of 2 eagles (Aquilasp.), 1 Common Kestrel (Falco tinnunculus), 1 Black Kite (Milvus migrans), and 3 Greater Flamingo (Phoenicopterus roseus). The conclusion was made that the BPDs of this OHL needed renewal. It was also concluded that instead of OHLs laid along the pipeline route it was advisable to consider other options, including stations of cathodic protection fed from modular-packaged electrical power plants with self-contained micro-turbine units, such as used at the Beineu – Bozoy – Shymkent Gas Pipeline.

STUDY OF HTA DISTRIBUTION NETWORK RELIABILITYIN NIAMEYCITY

With the growth of demand for electrical energy, electrical networks are nowadays subjected to very high loads, sometimes beyond their capacity. This leads to their malfunction and their inability to meet expectations. But given the importance of electricity in our lives, this disruption cannot be tolerated for long, which leads distribution operators to implement maintenance programs to ensure continuity of service. However, these measures, although extremely important, are time consuming, costly and sometimes do not provide complete satisfaction, resulting in the absence of electricity to consumers. The study of reliability of medium voltage distribution network in Niamey allowed us to analyze the performance indices of latter. Indeed, we based ourselves on the number of incidents (opening of HV outlets) and their duration while taking into account the origin of the associated disturbances. In the light of this analysis, the reliability of lines is close to 95% only for a period of one (1) hour (h) and is almost zero beyond 100 hours of operation. As for maintainability, it is only guaranteed within a period of 10 hours after the occurrence of incident on network.