Low-voltage Equipment Research Articles

The Evolving Technological Framework and Emerging Trends in Electrical Intelligence within Nuclear Power Facilities

This paper thoroughly explores the feasibility of integrating a variety of intelligent electrical equipment and smart maintenance technologies within nuclear power plants to enhance the currently limited level of intelligence of these systems and better support operational and maintenance tasks. Initially, this paper outlines the demands and challenges of intelligent electrical systems in nuclear power plants, highlighting the current state of development of intelligent electrical systems, including new applications of artificial intelligence and big data technologies in power grid companies, such as intelligent defect recognition through image recognition, intelligence-assisted inspections, and intelligent production commands. This paper then provides a detailed introduction to the architecture of intelligent electrical equipment, encompassing the smart electrical equipment layer, the smart control system layer, and the cloud platform layer. It discusses the intelligentization of medium- and low-voltage electrical equipment, such as smart circuit breakers, smart switchgear, and low-voltage distribution systems, emphasizing the importance of intelligentization in improving the safety, reliability, and maintenance efficiency of medium- and low-voltage distribution equipment in nuclear power plants. Furthermore, this paper addresses issues in the intelligentization of nuclear power plant electrical systems, such as information silos, the inefficiency of traditional manual inspection processes, and the lack of comprehensive intelligent design and evaluation standards, proposing corresponding solutions. Additionally, this paper presents the trends in intelligent operation and maintenance technology and applications, including primary and secondary fusion technology, intelligent patrol system architecture, intelligent inspection based on non-destructive testing, and a comprehensive solution based on inspection robots. The application of these technologies aids in achieving automated inspection, real-time monitoring, and the intelligent diagnosis of electrical equipment in nuclear power plants. Finally, this paper proposes basic principles for the development of intelligent electrical systems in nuclear power plants, including intelligent architecture, the evolutionary path, and phased goals and key technologies. It emphasizes the gradual transition from automation to digitization and then to intelligentization and presents a specific implementation plan for the intelligentization of the electrical systems in nuclear power plants. This paper concludes with a summary of short-term and long-term goals for improving the performance of nuclear power plant electrical systems through intelligent technologies and prospects for the application of intelligent technologies in the operation and maintenance of nuclear power plants in the future.

How effective is virtual reality for electrical safety training? Evaluating trainees’ reactions, learning, and training duration

Introduction: The widespread use and inherent risks associated with low-voltage electrical equipment require all workers to understand its hazards and how to manage them. Despite being the most commonly used method for raising safety awareness, lecture-based training often proves ineffective. Virtual reality (VR) allows the user to be immersed in a virtual environment and actively participate in practical training while maintaining their safety, which can potentially result in engaging and effective training. This paper investigates the effectiveness of using immersive VR for low-voltage (LV) electrical safety training to understand the potential benefits of VR technology for industrial safety training applications. Method: A within-group experimental design was employed with 18 participants undertaking the LV VR training. The effectiveness of the training was evaluated by measuring participants’ reactions, learning, and training duration. Participants’ learning was measured before, immediately after, and four weeks after the training, whereas reaction and suitability of training duration were measured after the training. Results: Participants reported highly positive reactions to the LV VR training, particularly regarding their level of engagement, intention to use the system in the future, and enjoyment. Knowledge test scores significantly improved immediately after training with high effect sizes. Although scores decreased significantly four weeks after training, they remained significantly higher compared to before training. The training duration, ranging from 29 to 44 minutes was considered suitable for the training. Conclusions: LV VR training effectively elicited positive reactions from trainees and supporting trainees to acquire and retain safety information while maintaining appropriate training duration. Practical Implications: VR emerges as a viable alternative training method worth exploring for organizations seeking to improve their safety training programs. VR combines educational and entertainment values, facilitating enjoyable learning experiences.

Multi Electrode Differential Voltage Sensor Based on Electric Field Coupling

With the increasing demand for electricity, voltage measurement has been applied in various fields of the power grid, especially in low-voltage distribution networks and household appliances. However, in low-voltage distribution networks, traditional contact measurement cannot be used due to technical limitations such as the need to damage the insulation layer. Non contact voltage measurement is becoming the main voltage measurement method, A major technical challenge in non-contact measurement is the interference of external electric fields. In order to solve the above problems, this article develops a new type of non-contact low-voltage measurement equipment, which can overcome the interference of external electric fields on measurement and achieve high-precision non-contact voltage measurement. The experimental results indicate that the sensor designed in this paper has high measurement accuracy. The ratio error at power frequency is within ± 0.9%, and the phase error is within 3°. In addition, the sensor also has the advantages of low cost, small size, and convenient manufacturing.

Considerations regarding testing of low voltage equipment at electrical arc and thermal factor actions

Within paper there is made a synthesis of IEC standards requirements for testing at overload and short-circuit currents of low voltage equipment: switches, disconnectors, switch- disconnectors, contactors, fuses and fuses combinations with these. After this there is presented testing circuit for withstand ability at overload and short-circuit currents passing of low voltage equipment for a large range of currents through realisation of a special circuit for load adjustment. Also are described experiments performed on low voltage fuses - as type tests - and are established appreciation criteria regarding the behaviour at electric arc action due to overload and short-circuit currents.

Comparison of Low-Voltage Arc-Resistant Equipment, Equipment with Isolation Barriers, and Equipment with Energy-Reducing Line-Side Isolation for Reduction of Arc-flash Hazards

Comparison of Low-Voltage Arc-Resistant Equipment, Equipment with Isolation Barriers, and Equipment with Energy-Reducing Line-Side Isolation for Reduction of Arc-flash Hazards

Results of a statistical study of types of single-phase faults in low-voltage ship electrical networks

The increase in the power supply of ships is manifested in growth of ship power plants' capacity, the total length of cable lines, and the number of electrified mechanisms. With the development of marine technology, the severity of the consequences of damage to ship electrical equipment and the costs of its maintenance and repair increase. The search for ways to improve the reliability and safety of electrical equipment should be based on design and technological solutions at the stages of its development and production, as well as an analysis of various factors that may appear during the operation of marine equipment and affect the condition of ship electrical systems. During studying these factors, it has been revealed that one of the common types of damage to electrical equipment of marine equipment is single-phase short circuits, the causes of which are varied. Preventing short circuits is labour intensive and in some cases impracticable. However, understanding the characteristics of this type of damage to low-voltage equipment is necessary to improve the reliability and safety of ship electrical systems. The conducted research is based on a survey of ship electrical mechanics. The results of the surveys have made it possible to analyze the frequency of occurrence of single-phase insulation faults, the duration of their existence, to identify the most likely places of occurrence of short circuits and equipment that is more susceptible to such damage compared to other elements of the electrical power system.

A study of the impact of voltage sag on sensitive loads at low-voltage distribution areas

Under the background of the dual carbon goal and the new power system, the power system becomes more complex and diverse, and voltage sag events caused by short-circuit faults, overloads, switching operations, large motor starting, and distributed generation access are more frequent. On the other hand, with the increasing sensitivity of low-voltage distribution network electrical equipment to power quality, especially for precision process control equipment using computers, power electronics, and automation technology, new energy generating units, and electric vehicle charging facilities, voltage sag accidents will cause difficult-to-estimate losses in equipment production and operation, and frequent voltage sag events have become one of the main power quality problems affecting reliable power supply and normal equipment operation. To address this problem, this paper analyzes the impact of voltage sag on low-voltage substation loads from a mechanism perspective, establishes a voltage sag tolerance curve for electronic appliances through experimental research, and simulates and verifies the effectiveness and correctness of the method in this paper using a 3 MW-rated induction generator connected to the distribution network as an example.

Power Quality Analysis for Light-Duty Electric Vehicles: A Case Study in Malta

This paper presents a power quality analysis for multiple electric vehicle charging stations of the AC-Level 2 type in a real-life case study. The data was collected with a power quality analyzer that measured the main distribution system feeding nine 7 kW charging stations in a commercial site with light-duty vehicles in Malta, Europe. The relevance of this study to the specific case of Malta is accentuated by the topological challenges of the country; high density of road vehicles, with 18,000 vehicles for each square kilometer; and ambitious targets of reaching carbon neutrality by 2050. Data were collected over six days on an actual charging system with real-life charging patterns. Various results are presented in this paper, including three-phase system voltages and currents, individual harmonic voltage and current components, total harmonic distortion and total current demand distortion. These measurements were compared with standardized thresholds for low-voltage equipment used in public spaces, mainly as stated in IEEE 519-2014.

Lightning Surge Overvoltage Protection for Low-Voltage Equipment Placed Outdoors in TT System

When a TT system is used for earthing a low-voltage distribution line, the conductive enclosure of the equipment is grounded separately from the system ground for the power line. In such a case, lightning protection depends on the installation of surge protective devices (SPD) on the equipment side. However, in newer systems, a protective earth (PE) line is wired from the power substation for stable operation and connected to the PE line in the outdoor equipment. In this case, the SPD of the distribution board can suppress the overvoltage on the equipment side. In this article, the overvoltage generated between the power and grounded PE lines of the equipment using a vinyl-insulated vinyl-sheathed flat-type cable for a low-voltage distribution line was examined using transient circuit analysis. Then, we demonstrated countermeasures to achieve electric shock and lightning overvoltage protection.

접지 전위 간섭의 특성을 반영한 접지저항 측정 방법

Domestic low-voltage electrical equipments have an environment prone to ground potential interference, due to the characteristics of grounding system. This ground potential interference affects electrical equipments and communication facilities, and amplify the error of ground resistance measurement. It is desirable to find and eliminate the root cause of ground potential interference, however it is difficult to remove that in an environment such as in a dense urban area or an area adjacent to the transmission line. In this paper, the pattern of the potential interference voltage and the effect on the conventional ground resistance measurement are analyzed based on the actual field measurement cases of the ground potential interference, and propose a ground resistance measurement method that reflects the characteristics of ground potential interference.

Моделирование потерь мощности в контактных системах низковольтных коммутационных аппаратов

The article studies the dependences of active power losses in contacts and contact systems of circuit breakers, contactors and magnetic starters on the main parameters of electrical equipment. Models of functional dependences of active power losses on nominal current for low-voltage switching devices of some manufacturers are developed. Approximation functions of these characteristics have been compiled and the value of determination coefficient of the obtained functions of active losses and approximation error have been calculated. Graphical dependences of the investigated parameters of low-voltage equipment are presented.

Engineering and design of a novel high-current source for testing low-voltage electrical equipment

This article presents the specification and design of a low-voltage high-current source with a capacity of up to 65 kA and 1 kV for testing electrical equipment such as low-voltage power circuit breaker switchgear, metal-enclosed switchgear, transformers, and cables, among others. Tests that can be performed with the proposed source include the short-circuit withstand on the low-voltage side of transformers, verification in temperature rise limits on electrical power connectors and transformers, and other compliance tests on power circuit breaker switchgear and controlgear assemblies. The design results from the comparison of general topologies of high-current sources according to the literature and test requirements established in current IEEE and IEC standards. In addition, the low-voltage high-current source emerged as a need for the Colombian electricity sector and will help comply with the test guidelines for switchgear and other low-voltage equipment, according to the national standard, also contributing to reducing costs of conducting tests abroad. The specification of the source resulted in the definition of three operating ranges for different types of tests, equipment, voltage, and current levels. Moreover, the general scheme of the low-voltage high-current source is provided with a description of the major components, namely, the novel medium- and low-voltage power modules based on the parallel and series arrangements of toroidal transformers to obtain levels of current and voltage of up to 65 kA and 1 kV, and the switching and protection, control, and measurement systems. Finally, a discussion of the results is presented, and the conclusions are highlighted. © 2017 Elsevier Inc. All rights reserved.

Smart Predictive Maintenance Device for Critical In-Service Motors

The paper proposed an innovative predictive maintenance system, designated to monitor and diagnose critical electrical equipment (generally large power electric motors) within industrial electrical installations. A smart and minimally invasive system is designed and developed. Its scope is to evaluate continuously the essential operating parameters (electrical, thermal, and mechanical) of the investigated equipment. It manages to report the deviations of inspected machine operating parameters values from the rated ones. The system also suggests the potential cause of these abnormal variations along with possible means (if the defect is identified in a database, constantly updated with each appearance of a malfunction). The developed maintenance device generates an operating report of the analyzed equipment, in which the values of power quality and energy indicators are computed and interpreted. Additionally, real-time remote transmission of analyzed data is facilitated, making them accessible from any location. The proposed maintenance system is a low-cost device that is easy to install and use in comparison with similar existing devices and equipment. The designed maintenance system was tested on dedicated to low-voltage equipment up to 100 kW.

Lightning Damages of Low-voltage Electrical Equipment in Tohoku Region

Lightning Damages of Low-voltage Electrical Equipment in Tohoku Region

Study on partial discharge characteristics of C6F12O mixed gas

The greenhouse effect of SF6 increasingly limits its application in various gas insulated equipment. C6F12O combines the advantages of insulation resistance, safety and environmental protection. When mixed with buffer gas, C6F12O is considered to have potential application prospects in medium and low voltage equipment. In this paper, about the partial discharge characteristics of the mixed gas, an experimental study was carried out. The partial discharge initiation voltage and discharge extinction voltage of mixed gas under power frequency voltage are measured and compared with the breakdown voltage. The results show that the breakdown voltage is greatly improved after adding C6F12O, with the increase of mixing ratio, the partial discharge initiation voltage and extinction voltage of mixed gas gradually increase, and the effect of gas pressure on high mixing ratio is obvious. The difference between the partial discharge inception voltage and the breakdown voltage is larger than that of pure N2. The research in this paper can provide an important reference for the application, operation and protection of C6F12O mixed gas in medium and low voltage equipment.

Engineering and Design of a Novel High-Current Source for Testing Low-Voltage Electrical Equipment

Engineering and Design of a Novel High-Current Source for Testing Low-Voltage Electrical Equipment

Resistance change of contact groups of low-voltage electrical apparatus: Determining the laws

The main Russian and foreign manufacturers of low-voltage electrical devices - circuit breakers, fuses, magnetic starters, knife switches and packet switches are presented. The data of experiments for determining the resistance values of contact groups of low-voltage switching equipment are considered. The design features of the devices that determine the value of the resistances of the power circuits of low-voltage equipment are investigated and a classification is proposed depending on the design elements of the devices. A methodological approach and an algorithm for experiments and detailed analysis of the contact groups of devices are given. Experimental schemes for the study of contact groups are proposed. The data of the conducted experiments on the study of contact groups and the resistance values as a function of the flowing currents are shown. During the experiments it is revealed that the value of the resistance of the contacts changes depending on the value, type and time of exposure to current within +/-5 %. The laws that characterize the ratio of the resistance values of the structural components of devices (contact systems, thermal relay, coil of the maximum relay) have been revealed and defined. Empirical expressions and graphical dependences of the resistances of contacts and contact systems are obtained as a function of the magnitude of the rated currents of low-voltage contact equipment. The minimum sample size of the number of devices during experimental research is determined, sufficient to calculate the mathematical expectation of the resistances of the contact connections of the devices with a given accuracy. As a result of experimental studies, it is revealed that the resistance value of contacts and contact joints can increase during operation by 2-2.5 times. The established dependences of the change in contact resistance can be used to predict the technical state of electrical installations of intrashop low-voltage networks, to clarify the amount of electricity losses in shop networks up to 1 kV, and can also be used as an additional regulation for maintenance and scheduled preventive maintenance.

Результати тестування доїльної установки типу «ЯЛИНКА» «EUROCLASS 1200»

Abstract The purpose of the research is – to evaluate the milking platform of "Yalynka" ("Herringbone") "EuroClass 1200" type manufactured by "GEA" (Germany) for milking cows based on the results of experimental testing. Research methods. During the testing of the milking parlor "Yalynka" "EuroClass 1200" type the quality of the technological process was determined using the methods described in ISO 5707:2007, ISO 6690:2007, DSTU 7435:2013 and DSTU 3662:2018, operational-technological and economic evaluation was carried out according to DSTU 8424:2015 and DSTU 4397:2005, safety and ergonomics of the equipment were determined according to DSTU EN ISO 12100:2014. Research results. According to the results of experimental testing, it was established that the milking parlor "Yalinka" "EuroClass 1200" type of German production at the appropriate level performs the technological process of machine milking of cows. The obtained research results showed that the average total milking time of one cow is 5,07 minutes, the average intensity of milk excretion as a whole during milking – 2,35 kg / min. Milk obtained during milking cows in terms of quality corresponds to the grade "Extra" in accordance with DSTU 3662: 2018. Devices for controlling the process of milking cows "DemaTron 70" and computer herd management system "Dairy Plan C21" perform the technological process of milking cows in automatic mode, control over the implementation of technical parameters of the milking process, milk accounting and shutdown of milking machines. Based on the results of conformity assessment of the construction of the milking parlor "Yalinka" "EuroClass 1200" type in terms of safety and ergonomics, it is established that it meets the requirements of DSTU EN 12100: 2014 and DSTU 60204-1: 2015 for items related to its design, which is the evidence base of its compliance with the Technical Regulations for the Safety of Machinery and the Technical Regulations for Low-Voltage Electrical Equipment. Productivity of the milking installation-platform makes 70 heads / hour. Serves the milking parlor 2 operators of machine milking. Electricity consumption per milking a cow is 0,13 kWh. Annual operating costs are 4247 UAH / head in the conditions of 3 times milking of cows. Conclusions. For the first time in Ukraine, experimental testing of the milking parlor "Yalinka" "EuroClass 1200" type showed that the equipment satisfactorily performs the technological process of machine milking of cows with their loose housing and provides milk of the "Extra" grade. The «Euroclass 1200» «Yalinka» milking parlor is characterized by a high technical level and can be widely used in Ukraine.

Graphite nanoplatelets filled silicone composites with novel electrical and dielectric properties

In the design of medium and low voltage equipment such as cable accessories, generator, motor end windings or bushings, issues with electrical field enhancement occur at interfaces between insulators and conductors, resulting in accelerated material ageing. The purpose of this paper is to present a novel dielectric composite material which has the properties to mitigate this local amplification. It is a functional dielectric which resistivity decreases by several orders with electric field from 1014 to 109 Ωm up to 1 kV mm−1 while the dielectric constant decreases from 15 to 12 in the 10–2–106 Hz range. This novel material is made with graphite nanoplatelets. It may be used as a resistive or capacitive field grading material in electrical applications.

Automatic Grounding Protection Technology for Low-Voltage Cable in Distribution Network Without Power Outage

With the continuous development of science and technology, the current era of low-voltage cable equipment has changed earthshaking compared with the traditional power failure equipment, and has a more significant application in the distribution network control system, effectively improve the work efficiency of power failure equipment. The rapid development of high voltage technology also provides a platform for the application of low voltage cable equipment. By expatiating the characteristics and present situation of the low-voltage cable equipment, this paper analyzes the application problems in the design of the non-power outage equipment system, and puts forward practical suggestions for readers’ reference.