Acoustic waves produced by partial discharges inside in dielectric materials can be detected using acoustic emission (AE) sensors. This detection can be analyzed in the time domain. AE sensors are immune to electromagnetic interference and provide a nonintrusive and nondestructive detection and a galvanic decoupling with respect to the electric network. This work presents the experimental results of AE sensors characterization and the online detection capability in the environment near cable accessories. The AE technique of partial discharge detection can be applied as a test method for preventive or predictive maintenance (condition-based maintenance) to equipment or facilities of medium and high voltage. Represents an alternative method to electrical detection systems, conventional or not, who continue to rely on the detection of current pulses. This paper presents characterization tests of the sensors AE through comparative tests of partial discharge on accessories for underground power cables

Visual corona tests are useful to identify the critical corona points of different high‐voltage components. Radio interference voltage and partial discharge measurements also allow detecting corona activity. However, these techniques require expensive screened laboratories, sophisticated instrumentation and usually do not provide the exact location of the discharges. Corona tests are often performed in external laboratories, where customers habitually have to face long waiting times. The tests in such laboratories must be totally planned beforehand, as they are habitually done by external engineers, so little information about the behaviour and possible modifications of the product is acquired by the customer. This study proposes a feasible solution to perform routine corona tests, while greatly reducing the voltage applied, laboratory size and requirements, testing times, and thus test costs. This study also detects the visual corona onset by means of a commercial digital camera, which allows locating the critical corona points, thus greatly decreasing the costs of the corona instrumentation, while maintaining the accuracy and sensitivity of the detection method. The methodology proposed in this study can be applied to many other high‐voltage devices such as conductors, vibration dumpers, corona protections and different types of hardware and fittings for power lines and substations.

This paper presents a novel voltage sag topology that occurs during an unintentional islanding operation (IO) within a distribution network (DN) due to large induction motors (IMs). When a fault occurs, following the circuit breaker (CB) fault clearing, transiently, the IMs act as generators due to their remanent kinetic energy until the CB reclosing takes place. This paper primarily contributes to voltage sag characterization. Therefore, this novel topology is presented, analytically modelled and further validated. It is worth mentioning that this voltage sag has been identified in a real DN in which events have been recorded for two years. The model validation of the proposed voltage sag is done via digital simulations with a model of the real DN implemented in Matlab considering a wide range of scenarios. Both simulations and field measurements confirm the voltage sag analytical expression presented in this paper as well as exhibiting the high accuracy achieved in the three-phase model adopted.

Substation connectors play a key role in the reliability of power transmission systems. Despite this fact, their behavior has been rarely studied, especially in regard to electric stress. In this study the corona inception voltage of a complex-shaped 765 kV substation connector is calculated by using a three-dimensional finite-element approach combined with the semi-empirical Pedersen approach. The method proposed was previously validated by using available experimental data obtained from sphere-to-plane, concentric cylinders and point-to-plane non-uniform air gaps. To further validate the accuracy of this method, the corona inception voltage of the analyzed substation connector was obtained by making comparisons with experimental tests conducted in a high voltage laboratory. Results show the need to calculate the corona inception voltage for complex geometries and large air gaps. Using this proposed approach allows us to identify peak or stress points of the connector surface. Hence, this system strongly appears to be a valuable tool to assist the design process of substation connectors and other high voltage devices for minimizing corona activity.

Studies within the European Higher Education Area framework include the acquisition of skills such as the ability to learn autonomously, which requires students to devote much of their time to individual and group work to reinforce and further complement the knowledge acquired in the classroom. To consolidate the results obtained from classroom activities, lecturers must develop tools to encourage learning and facilitate the process of independent learning. The aim of this paper is to present the use of virtual laboratories based on Easy Java Simulations to assist in the understanding and testing of electrical machines.

Corona is a critical effect that must be considered during the design and optimisation stages of high‐voltage hardware such as substation connectors, since due to the harmful effects, corona threats power systems reliability. Visual corona tests allow detecting and identifying the critical corona points on the surface of substation connectors, so corrective actions can be applied for product optimisation. This article focuses on reduced‐scale (RS) visual corona tests intended to verify and optimise the behaviour of such high‐voltage hardware. RS visual corona tests allow reducing the voltage to be applied, laboratory size, instrumentation requirements, assembly, and test times, and finally the overall costs of the tests compared to standard corona tests carried out in large‐size high‐voltage laboratories. A hybrid approach combining experimental tests and finite element method (FEM) simulations is presented, which allows obtaining the equivalent visual corona onset voltage between RS and full‐scale tests. Although the article focuses on the analysis of aluminium substation connectors, the proposed approach can be applied to many other hardware intended for high‐voltage applications.