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The dependable functioning of switchgear is essential to maintain the stability of power supply systems. Partial discharge (PD) is a critical phenomenon affecting the insulation of switchgear, potentially leading to equipment failure and accidents. PDs are generally grouped into metal particle discharge, suspended discharge, and creeping discharge. Different types of PDs are closely related to the severity of a PD. Partial discharge pattern recognition (PDPR) plays a vital role in the early detection of insulation defects. In this regard, a Back Propagation Neural Network (BPNN) for PDPR in switchgear is proposed in this paper. To eliminate the sensitivity to initial values of BPNN parameters and to enhance the generalized ability of the proposed BPRN, an improved Mantis Search Algorithm (MSA) is proposed to optimize the BPNN. The improved MSA employs some boundary handling strategies and adaptive parameters to enhance the algorithm's efficiency in optimizing the network parameters of BPNN. Principal Component Analysis (PCA) is introduced to reduce the dimensionality of the feature space to achieve significant time saving in comparable recognition accuracy. The initially extracted 14 feature values are reduced to 7, reducing the BPNN parameter count from 183 with 14 features to 113 with 7 features. Finally, numerical results are presented and compared with Decision Tree (DT), k-Nearest Neighbor classifiers (KNN), and Support Vector Machine (SVM). The proposed method in this paper exhibits the highest recognition accuracy in metal particle discharge and suspended discharge. [ABSTRACT FROM AUTHOR]

The explosion accident due to the internal arc fault in the metal‐enclosed switchgear cannot be ignored. Therefore, improving the ability of switchgear to resist the arc fault has important significance. In this paper, a passive protection measure by installing the buffer volume (BV) was proposed. The short‐circuit arcing tests were carried out in the small‐scale switchgear compartments, and the pressure rise was measured in the different models. The changes of pressure rise before and after installing BV were analyzed. Then, the calculation methods of pressure rise in the compartments and the mechanical response of the enclosure were put forward. By calculating the distributions of the pressure rise and temperature rise in the compartments, as well as the time‐varying displacement and stress of the enclosure, the pressure relief effect of the BV has been discussed. Results show that after installing the BV, the pressure rise, displacement, and stress are all decreased obviously in the initial of arcing. Hence, the arc fault protection effect for the switchgear can be improved by properly installing the BV. [ABSTRACT FROM AUTHOR]

The basic requirements for the design of a switchgear for main 35–220 kV step-down substations are reliability and efficiency. Switchgear circuits are chosen depending on the number of supply and transit lines and transformers, the substation's place in the power supply system, and the area that can be allocated under the substation construction. The substation switchgear's reliability depends on the circuit type and the equipment to be installed. When designing, as a rule, standard substation switchgear circuit solutions are chosen with often unreasonably overstated reliability indicators and, as a consequence, capital costs. This paper explores the issues of automated choice of the best option for the 35–220 kV substation switchgear circuit, considering its structural reliability and additional costs for the area allocated under the electrical unit. A distinctive feature of the work is a comprehensive accounting of the reliability indicators of the substation and the influence of the layout of switchgear circuits as a whole on the performance indicators of future electrical installations. The developed technique is used at the pre-design stages and allows for reducing further capital, maintenance, and repair costs for electrical units by up to 14.5%. The developed approach is implemented in the original TER CAD software product. [ABSTRACT FROM AUTHOR]

To improve the insulation diagnosis of a medium-voltage (MV) switchgear, we have developed a four-terminal surface current sensor and a method to estimate the direction of partial discharge occurrence. In this method, the accuracy of the direction estimation is improved by referring only to the direct wave, and the error due to noise can be suppressed by calculating the outputs of the four terminals. The experimental results demonstrate that the detection characteristics of the sensor concur well with the theoretical characteristics derived from the detection principle. Additionally, we conducted an experiment using the developed sensor and the new method to detect the surface current generated due to partial discharge occurring in a rectangular enclosure. The results demonstrate that the occurrence direction could be estimated even for a rectangular enclosure. Furthermore, the propagation attenuation of the surface current at the corners of the enclosure was large, exhibiting an attenuation 0.25 times for the worst case. Finally, it was confirmed that noise removal using a wavelet transform could reduce the direction estimation error of the discharge occurrence by approximately half. [ABSTRACT FROM AUTHOR]

The restrike of vacuum circuit breaker during the breaking process causes overvoltage and intensifies the insulation deterioration of high‐voltage equipment. To solve this problem, the vacuum breaker aging test method and the restrike characteristics are researched. A withstand voltage test platform of 40.5‐kV vacuum circuit breaker was established to obtain the effects of the contact spacing and loop and inrush currents of vacuum circuit breaker on the number of restrike, the wavefront steepness of the breakdown voltage, and the breakdown duration. The number of restrike during the breaking of vacuum circuit breaker decreased and the duration of the repeated‐breakdown arc increased with the increased contact spacing of vacuum circuit breaker. As the loop current of the test system increased, the number of restrike during the breaking of vacuum circuit breaker, the wavefront steepness of the breakdown voltage, and the duration of the restrike arc increased. As the inrush current amplitude increased during the closing of vacuum circuit breaker, the number of restrike and the duration of the repeated‐breakdown arc during the breaking of vacuum circuit breaker increased. The results provide a theoretical basis and data support for the preventive test of 40.5‐kV vacuum circuit breaker and the optimization of the withstand voltage test. [ABSTRACT FROM AUTHOR]

Pre-insertion resistor (PIR) is an important component of circuit breaker. The healthiness of the circuit breaker (CB) depends upon that of PIR contact. With the increasing demand of uninterrupted power supply, failure in major equipment like CB may incur huge loss to the utility. The existing study reveals that mechanical failures are more dominant than other types of failures. Thus, many industries prefer to undertake preventive maintenance of equipment rather than break down maintenance. This paper describes the actual problem detected in PIR contact of North Eastern Regional Transmission System, having a 400 kV, 3000 A, SF6 CB through testing and rectification thereafter. The results obtained from the graph helped in detecting mechanical dis-alignment of the connecting link in the link arm and the tubular contact of the PIR. Furthermore, a model has been developed to show the possible threat that would have occurred, had the problem been not rectified. This paper will help the utilities to emphasize on detecting the problem by undergoing preventive maintenance and thereby saving unprecedented failure of equipment. [ABSTRACT FROM AUTHOR]

The article presents the results of laboratory measurements of Ud breakdown voltages in a high-voltage vacuum insulating system for different pressures, contact gaps, type of electrode contacts and type of residual gas inside the discharge chamber. First of all, the electrical strength of the discharge chamber with a contact system terminated with contact pads made of W70Cu30 and Cu75Cr25 material was compared for selected values of contact gaps. It was found that below a pressure of p = 3.0x10-1 Pa the electrical strength reaches an approximately constant value for each of the set contact gaps d. Analytical relationships were determined to calculate this value for each of the contact pads used. Above a pressure of p = 3.0 x 10-1 Pa, the measured values of Ud breakdown voltages decrease sharply. The values of breakdown voltages in the discharge chamber with residual gases in the form of air, argon, neon and helium were also determined for selected values of contact gaps d. Depending on the residual gases used, significant differences were noted in the values of pressure p at which the loss of insulating properties in the discharge chamber occurred. These values were 3.3 x 10-1 Pa for argon, 4.1 x 10-1 Pa for air, 6.4 x 10-1 Pa for neon, and 2.55 x 100 Pa for helium, respectively. [ABSTRACT FROM AUTHOR]

Traditional switchgear current measurement techniques use closed-loop current modules to accurately measure and control current, and in switchgear, there is also interphase interference, these modules usually require a large core that surrounds the entire busbar as well as a shielded shell, because the compensation current generated inside the module is proportional to the busbar current, so the power consumption can be as high as several watts. In view of this, this paper proposes a magnetic sensor-based switch cabinet busbar current measurement method, and through theoretical deduction, it is determined that the magnetic sensor with two magnetic sensitive directions opposite and vertically placed in the busbar can eliminate the interference from the busbar phase and the stray field. Through simulation analysis, it was determined that the opening hole of the switch cabinet bus row was a circular hole, and the placement of the two magnetic sensors was at the edge of the circular hole, so that the practical application of the method in the switch cabinet had certain guiding significance. [ABSTRACT FROM AUTHOR]

In the authors' previous research, a new method for partial discharge detection in the switchgear based on near-field detection was proposed. The content of this paper is the continuation of the authors' previous research. In order to realize the reasonable layout of the near-field magnetic field probe for partial discharge detection in the switchgear, this paper simulates and analyzes the influence of the internal structure of the switchgear on the near-field propagation characteristics of the electromagnetic wave signal generated by partial discharge, and determines the installation position of the near-field probe in the switchgear. Firstly, the propagation characteristics of electromagnetic wave signals in the different media of the switchgear are analyzed, and the switchgear model is established. Then, based on the finite difference time domain method, the influence of different devices in the switchgear on the near-field propagation of the partial discharge electromagnetic wave signal is simulated. The simulation results show that the current transformer, insulator, busbar and cabinet all obviously attenuate the amplitude of the near-field electromagnetic wave signals generated by partial discharge, and the insulator causes obvious signal distortion. Finally, it is determined that the near-field probe can be installed on the inner wall or the right wall near the bottom plate of the switchgear. [ABSTRACT FROM AUTHOR]

The damaging effects of corona faults have made them a major concern in metal-clad switchgear, requiring extreme caution during operation. Corona faults are also the primary cause of flashovers in medium-voltage metal-clad electrical equipment. The root cause of this issue is an electrical breakdown of the air due to electrical stress and poor air quality within the switchgear. Without proper preventative measures, a flashover can occur, resulting in serious harm to workers and equipment. As a result, detecting corona faults in switchgear and preventing electrical stress buildup in switches is critical. Recent years have seen the successful use of Deep Learning (DL) applications for corona and non-corona detection, owing to their autonomous feature learning capability. This paper systematically analyzes three deep learning techniques, namely 1D-CNN, LSTM, and 1D-CNN-LSTM hybrid models, to identify the most effective model for detecting corona faults. The hybrid 1D-CNN-LSTM model is deemed the best due to its high accuracy in both the time and frequency domains. This model analyzes the sound waves generated in switchgear to detect faults. The study examines model performance in both the time and frequency domains. In the time domain analysis (TDA), 1D-CNN achieved success rates of 98%, 98.4%, and 93.9%, while LSTM obtained success rates of 97.3%, 98.4%, and 92.4%. The most suitable model, the 1D-CNN-LSTM, achieved success rates of 99.3%, 98.4%, and 98.4% in differentiating corona and non-corona cases during training, validation, and testing. In the frequency domain analysis (FDA), 1D-CNN achieved success rates of 100%, 95.8%, and 95.8%, while LSTM obtained success rates of 100%, 100%, and 100%. The 1D-CNN-LSTM model achieved a 100%, 100%, and 100% success rate during training, validation, and testing. Hence, the developed algorithms achieved high performance in identifying corona faults in switchgear, particularly the 1D-CNN-LSTM model due to its accuracy in detecting corona faults in both the time and frequency domains. [ABSTRACT FROM AUTHOR]

The main goal of the present study is to carry out one-way coupled computations of electromagnetics and heat transfer for a simplified version of a switchgear and to reveal the applicability of the computational approach. In our computation, we introduce the joule losses that we obtain from the electromagnetic computations to a thermal solver as heat load. In order to reach the goal, we compare the temperature values that we obtained at eight different measurement points by performing computations and experimental measurements. In general, the distributions of the obtained temperature values are quite similar. The notable difference in the mean values of the obtained temperatures might result from limitations of one-way coupled approach where we have to neglect temperature dependency of the electrical properties during the electromagnetic computations. [ABSTRACT FROM AUTHOR]

In power energy distribution networks, switchgear is considered critical equipment. This is because the act of monitoring the operation and condition of switchgear, as well as performing the required corrective maintenance on any potentially problematic equipment, is critical. A single event may harm thousands of customers over time and pose a significant risk to operational staff. Many considerations must be put in place before using outages to switch down the system since they may raise maintenance costs and disrupt the power supply to users. As a result, proper interpretation of switchgear status evaluations is critical for the early identification of possible faults. Existing ultrasound condition-based monitoring (CBM) diagnostic testing techniques require the tester to manually interpret test data. This study aims to review the status of the recent development of CBM techniques with faults in switchgear. The current trend in electrification will be toward the safety and sustainability of power grid assets, which involves an evaluation of the electrical systems' and components' health and grids for medium-voltage distribution. This work provides a current state-of-the-art evaluation of deep learning (DL)-based smart diagnostics that were used to identify partial discharges and localize them. DL techniques are discussed and categorized, with special attention given to those sophisticated in the last five years. The key features of each method, such as fundamental approach and accuracy, are outlined and compared in depth. The benefits and drawbacks of various DL algorithms are also examined. The technological constraints that hinder sophisticated PD diagnostics from being implemented in companies are also recognized. Lastly, various remedies are suggested, as well as future research prospects. [ABSTRACT FROM AUTHOR]

This work aims to detect the discharge products and study the decomposition characteristics of C5F10O/N2 gas mixture under pulsed discharge. Discharge tests are carried out on three kinds of gas mixtures with different contents of C5F10O (3.3%, 10%, and 30%). Electron attachment mass spectrometry (MS) is proposed to detect discharge products after negative ionization, and the results are compared with that in gas chromatography (GC) MS. The discharge products are detected and the formation pathways of the main decomposition products are deduced. The results show that the densities of some products increase with the number of discharge pulses. There are differences on the types of products and the cumulative effect of discharge in the three kinds of gas mixtures. Furthermore, these discharge products are able to characterize the discharge accumulation effects in power switchgear, such as insulation degradation. [ABSTRACT FROM AUTHOR]

Corona discharge occasionally occurs to the contact box of switchgear due to condensation under high humidity and pollution conditions, which may result in a switchgear insulation fault. In this article, we develop an experimental platform for the condensation of contact boxes in switchgear. A metallographic microscope is used to measure the size and distribution characteristics of dewdrops on the surface of the contact box under various temperature, humidity, and pollution conditions. A simulation model for the distribution of dewdrops is established using fractal theory, and the simulation results match the measured results well. The corona onset voltage is predicted and verified by the UV imager’s measurements by substituting the electric field distribution around the contact box with different dewdrops into the streamer inception criterion. The research results indicate that higher humidity and temperature differences result in a larger dewdrop and a shorter condensation formation time, resulting in a lower corona onset voltage. The effect law is similar under high pollution conditions, but the dewdrop is larger, the condensation formation time is longer, and the corona onset voltage is significantly lower than under clean conditions. As a result, high humidity and pollution conditions must be avoided during the operation of switchgear. [ABSTRACT FROM AUTHOR]

The integration of overhead lines in future MTDC grids leads to a higher fault rate compared to cables. Most of the faults are considered to be non-permanent, so that the line can be reconnected after dielectric recovery. The auto-reclosing procedure in HVDC systems reveals new challenges since multiple restrikes are possible within a short period of time. This paper proposes an auxiliary circuit for DC Circuit Breakers (DCCB) which enables to use the DCCB internal capacitor for the line pre-energization. A comprehensive description of the switchgear operations during the pre-energization sequence is provided and the fault property identification method is defined. The method is validated by simulations in a MTDC grid and a sensitivity analysis is carried out using EMTP-RV. [ABSTRACT FROM AUTHOR]

This paper presents the possibilities of reducing emergency situations and reducing the time of failure in the power grid. The paper contains a detailed description of the method (algorithm) of operation in emergency situations on the example of a Gas-Insulated Switchgear (GIS) located in one of the system-forming (node) stations in the power grid. The level of detail contained in this paper, which has not been previously encountered in previous publications, favors an in-depth understanding of the possible solutions that result from these emergencies. The above method (algorithm) of activities has been developed based on three levels of research: simulation, theoretical and practical. This means that the simulation analysis that was performed based on theoretical information was experimentally tested as part of an emergency situation in one of the system-forming (nodal) stations in the power system. In order to achieve the result described in this article, one of the most promising types of devices used in power systems was selected - the GIS. This has been confirmed by numerous analyzes of the effectiveness of these devices included in this article. The paper contains a detailed description of the individual steps in the field of corrective actions and aimed at minimizing downtime. In addition, this article provides guidance to monitor possible emergencies that are designed to increase the reliability of the power grid. [ABSTRACT FROM AUTHOR]

This work proposes a methodology to automate the recognition of Partial Discharges (PD) sources in Electrical Distribution Networks using a Deep Neural Network (DNN) model called Convolutional Autoencoder (CAE), which is able to automatically extract features from data to classify different sources. The database used to train the model is constructed with real defects commonly found in MV switchgear in service, and it also includes noise and interference signals that are present in these installations. PD sources consist of defective mountings, such as the loss of sealing cap of cable terminations, or an earth cable in contact with cable termination insulation. Four sources were replicated in a Smart Grid Laboratory and on-line measurement techniques were used to obtain the PD signal data. The Continuous Wavelet Transform (CWT) was applied to post-process the PD signal into a time-frequency image representation. The trained model predicts with high accuracy new data, demonstrating the effectiveness of the methodology to automate the recognition of different partial discharges and to differentiate them from noise and other interference sources. [ABSTRACT FROM AUTHOR]

C5-fluoroketone (CF3C(O)CF(CF3)2, abbreviated C5-FK) and C4-fluoronitrile [(CF3)2CFCN, abbreviated C4-FN] mixed with background gases such as carbon dioxide, oxygen, or air are used as alternatives to SF6 as the insulating and switching medium in high voltage gas insulated switchgear (GIS) due to their good switching and dielectric insulation performance and comparably low global warming potential (GWP). Like SF6, C5-FK and C4-FN are chemically stable inside electrical equipment and non-flammable. Like most complex molecules, they decompose exothermically when exposed to sufficiently high temperatures and do not recombine after decomposing. In this work, we use a custom-built test device to experimentally investigate the conditions and gas compositions under which a decomposition reaction can proceed to completion in C5-FK- and C4-FN-based gas mixtures after being initiated by an electric arc. We also present the related theory. The results show that, for properly selected mixtures, even under extreme failure conditions—internal arc faults—complete decomposition of the C5-FK or C4-FN does not occur. [ABSTRACT FROM AUTHOR]

Temperature rise simulation deals with different physical domains describing heat generation and heat dissipation effects. Cigré working group A3.36 has conducted a study on temperature rise simulation of switchgear for distribution and transmission level. The working group built up new, manufacturer independent devices. Members of the working group simulated the temperature rise in advance to the tests, which were performed at laboratories of universities, as independent parties. In order to assess the simulation accuracy, the simulation results are compared to each other and to the measured results. This paper summarizes the main findings from the medium voltage device. The study has shown that when simulating the temperature rise on a completely new design, with reliable input values of contact resistances and emissivity coefficients, an accuracy of about 25% could be expected. Primary reason seems to be based on the complexity of simulating the heat dissipation mechanisms. To get a more accurate result, verification and validation is needed in order to adjust the parameters determining the heat dissipation. This study has also illustrated that it requires good knowledge (especially of the radiation) in order to adjust these parameters properly. [ABSTRACT FROM AUTHOR]

In order to improve the accuracy of temperature prediction of switch gear equipment, a method for temperature prediction of switch gear equipment based on LSTM recurrent neural network is proposed. Firstly, obtain the relevant data set of the power switch gear equipment, and analyze and select the characteristic variables and data preprocessing of the original data set. Secondly, the processed data set is input to the LSTM recurrent neural network for training, and an LSTM temperature prediction model is obtained. Finally, taking the bus equipment of 6 kV switchgear as an example, and a comparison experiment of device temperature prediction is performed with various prediction algorithms. The experimental results show that: By comparing with the traditional neural network and classic recurrent neural network (RNN) temperature prediction model, the method proposed in this paper has higher accuracy for the temperature prediction of the equipment in the switchgear. It provides an effective way for active predictive maintenance. [ABSTRACT FROM AUTHOR]

This work describes the thermal design of a low-voltage switchgear based on a bus plate formed by a laminated bus plate structure. It has been done within the frame of developing a new generation of low voltage switchgear system, and the main goal was to provide the scientific verification of the new bus plate concept. The work consisted of thermal network and finite element simulations, aiming to gain understanding of the thermal behavior of the different parts of the system, and leading to the design and dimensioning of the conductors. The thermal performance has been confirmed by temperature rise tests. [ABSTRACT FROM AUTHOR]

Gas insulated metal enclosed switchgear (GIS) has been widely used in the world because of its compact structure and adaption to the environment. However, due to frequent operation and other reasons, GIS disconnector is prone to mechanical failure with poor contact, leading to abnormal vibration signals. In this paper, a GIS disconnector contact fault simulation platform is built to collect vibration signals in three states: normal contact, moderate poor contact and severe poor contact of disconnector contact. The Ensemble Empirical Mode Decomposition (EEMD) method is used to decompose the vibration signals, and the IMF decomposition signals are screened by Kurtosis criterion (a numerical statistic method). Finally, the vibration signal features of GIS under different conditions are obtained by reconstructing the screening signals. The results indicate that, under the normal contact, the frequency of GIS vibration signal mainly presents the distribution of 100 Hz and its integer multiple frequency component, when there is a contact defect, the high frequency component in the vibration signal spectrum increases significantly, and the tripling frequency component is present, and the amplitude of component will increase with the severity of the fault. Therefore, this study provides a theoretical reference for on‐line monitoring of GIS disconnecting switch contact fault. © 2021 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Free-moving conductive particles may affect the dielectric reliability of gas-insulated systems, e.g., gas-insulated lines (GIL) or gas-insulated switchgear (GIS). This paper reports on investigations on the behavior of free-moving particles under AC electric field, using different insulating gas mixtures. Multiple particles were positioned inside a GIL test setup with each particle placed within the same distance to a particle trap. To ensure reproducible and realistic particle geometry, cuboid particles were used. In this paper, a width correction factor was empirically determined for a well-known formula from the literature, which is used to calculate the lifting field strength for cuboid particles. While increasing the applied voltage, the movement of the particles was observed with a camera and further evaluated using ultra-high frequency (UHF) partial discharge (PD) measurements. The UHF phase-resolved partial discharge (PRPD) patterns of steel and aluminum particles in SF 6 , as well as in different alternative insulating gas mixtures, are compared and discussed. To determine the effectiveness of particle traps for different gas mixtures, further parameters are evaluated, such as the duration of each particle's movement and the number of particles reaching the inner conductor. [ABSTRACT FROM AUTHOR]

Electrical equipment will experience a rise in temperature during normal operation. During a development process, prototypes and laboratory tests will be required to make sure the temperature rises are within acceptable limits as defined by standards. The aim of having a tool to predict the temperature rise, is to reduce the number of prototypes and test loops needed in the laboratory during a development period. Advanced simulation tools such as CFD can give valuable results, however, they require expertise user and extensive compute and manpower allocation. This paper presents a practical design approach developed for providing a first, quick and rough estimate of the temperature rise of the most critical parts in an air insulated switchgear. The main idea behind the method is to first use the method described in IEC 60890 to estimate the temperature rise of the gas inside the switchgear. Then, simplified heat transfer calculations are used to estimate the over-temperature of critical parts relative to the surrounding gas. The accuracy of the temperature estimates will depend on how well the power input is known, especially the contact resistances. Further, it may be challenging to predict the influence of large metallic construction elements that may function as heat sinks. [ABSTRACT FROM AUTHOR]

Transformers are used in power systems to transform (step-down) voltages while maintaining the same frequency. Electrical engineers designing the power systems for a liquefied natural gas (LNG) or petrochemical facilities typically use two-winding transformers to feed multiple process units in redundant distribution schemes throughout the facility. This method is repeated further to derive different voltage levels to feed process loads. As the industry moves toward larger production facilities, which increase the power demand, multiple large two-winding transformers are utilized. This approach leads to an increase in substation footprint, switchgear equipment, power feeders, site works, etc. This article focuses on an alternative design using three-winding transformers for LNG and petrochemical facilities. The input and output of a three-winding transformer generally consist of one primary (H) input winding and two output windings defined as secondary (X) and tertiary (Y). The three-winding transformers are connected in a redundant configuration to feed multiple process units. In this article, different types of three-winding configurations and construction (radial or axial) methods are reviewed. In addition, this article addresses the application of tap changers, overall system performance, defining impedance parameters, and specification requirements. [ABSTRACT FROM AUTHOR]

The short‐circuit withstanding performance of busbar system is one of the most important safety indexes for low‐voltage (LV) switchgear. The resonance characteristics, short‐circuit displacement, and stress concentration of four typical busbar system arrangements are numerically analysed in this study. First, modal analysis is used to calculate the vibration modes and natural frequencies of the busbar systems. The influence of span length and phase‐to‐phase distance is discussed and thresholds for resonance prevention are given. Then, electromagnetic‐structural coupled models are built to simulate the short‐circuit mechanical response. The time‐varying displacement and stress are obtained and the dynamic stability of typical arrangements is compared. The proposed results can provide theoretical reference for the dynamic stability design of busbar system in LV switchgear. [ABSTRACT FROM AUTHOR]

Experimental investigation of the effect of filling pressure on the post-arc dielectric recovery characteristics of nitrogen is reported in this paper. A half-cycle arc current duration of 540 μs followed by a 10 kV pulse with a rise rate of 150 V/μs is applied across the contact gap. The pulse is applied from 10 μs to 10 ms after the current zero. First, a free-burning arc is studied without any forced gas flow. The effect of the gap distance on the recovery process is studied by using two different inter-electrode gaps: 20 mm and 50 mm. The effect of arc current on the recovery process is investigated by using current amplitudes of 275 A and 425 A. Moreover, the effect of forced nitrogen flow near current zero is explored using two different arrangements: self-blast and puffer type. Four different nitrogen filling pressures are studied: 1, 20, 40, and 80 bar, the latter two being in the supercritical region. The experimental results show that, in the free-burning arc configuration, the breakdown voltage of the contact gap increases faster with the increase of the filling pressure. A gap of 50 mm recovers quicker than a 20 mm gap, whereas no strong current dependency is observed on the recovery characteristics in the investigated range. In the free-burning arc configuration, just after the current zero up to approximately 300 μs, the breakdown voltage at high filling pressure is found to be lower than at 1 bar. Forced gas flow, however, significantly enhances the dielectric recovery at a high filling pressure, also in the thermal phase. [ABSTRACT FROM AUTHOR]

Numerical analysis has been applied to estimate the electric and electromagnetic fields in a medium voltage compact switchgear. The electric field evaluation enables to establish proper dimensions of the switchgear inner devices, e.g. bushing insulators. The electromagnetic field estimation with proposed (by the authors) models of main circuit connections leads to more accurate identification of Joule heating sources. These heat sources can be applied in the further thermo‐ventilation analysis. [ABSTRACT FROM AUTHOR]

Possible sulfur hexafluoride (SF6) gas alternatives have been the focus of research and development in science and industry for many years. After the revision of the European F-Gas regulation 517/2014, the investigation has been even more intensified. One option for an approach for realizing an environmentally friendly switchgear for the high-voltage level is a combination of gas circuit breaker (GCB) and vacuum circuit breaker (VCB) in a series connection. Both switching concepts have advantages: the VCB can withstand very steep rising transient recovery voltages after current zero (CZ), while the GCBs are able to withstand high amplitudes of recovery voltage. In this investigation, the coupling and interaction of a series connection of a VCB and a GCB filled with carbon dioxide (CO2) is experimentally characterized in a basic study. The postarc current of the axial-magnetic-field-type VCB is identified as an important parameter influencing the interaction between both circuit breakers in the series connection and subsequently in the focus of the investigation. The different CZ behavior of a single VCB and a hybrid circuit breaker is compared. The voltage distribution across the two circuit breakers is the main assessment criterion for a series connection. In the first phase after CZ, the postarc current has a dominant influence on the voltage distribution; after that, a transition phase leads to capacitive voltage division phase. In order to control the voltage distribution, both capacitive and resistive voltage controls are investigated. [ABSTRACT FROM AUTHOR]

The research and development work toward a compact SF $_6$ -free load break switch for the medium voltage range has led to several design proposals. The interruption capability of three different nozzles and gas flow concepts with atmospheric air as the interrupting medium is compared and assessed. The three test switches are installed in circuits corresponding to the mainly active load and switch-fuse test duties of the 24 kV/630 A load break switch standard. A pressure tank is used to provide different air flow rates, and the interruption capabilities of the different flow concepts are compared with basis in the tank pressure required to give successful interruptions. Two hundred and seventy current interruption tests were carried out. Air flows directed radially onto the arc or swirling along the arc turn out to result in a substantially better interruption performance than when the air flows straight and parallel to the arc. Air flows corresponding to upstream over-pressures of a few tenths of a bar seem to be sufficient for an air-based load break switch rated for 24 kV/630 A. [ABSTRACT FROM AUTHOR]

Temperature is an important indicator to measure the health status of power switchgear equipment. Accurate temperature prediction of equipment in the switchgear can effectively grasp its operating status in advance. The traditional BP neural network can realize temperature prediction, but it is easy to fall into local minimum values during the training process，which affects the accuracy of temperature prediction This paper proposes a PSO-op- timized BP neural network to predict the temperature of equipment. Firstly?the power opera¬tion data set is preprocessed. Before the network training, the weight and threshold of the neural network are optimized by PSO to obtain the PSO-BP prediction model. Finally?the es¬tablished prediction model is applied to the temperature prediction for the switchgear equip- ment. The experimental results show that，compared with the traditional neural network temperature prediction method，the method proposed in this paper can effectively predict the temperature for equipment in the switchgear. This method provides an effective way for grid management from traditional preventive maintenance to active predictive. [ABSTRACT FROM AUTHOR]

Ablation-assisted current interruption is a candidate for improving interruption capability in medium-voltage switchgear. In high-voltage switchgear, ablation is utilized to achieve high pressures in self-blast circuit breakers. Self-blast switch technology adapted to medium voltage could represent an attractive alternative to SF6 technology in load current interruption. However, the arc energies involved would be much lower than in fault current interruption, where self-blast technology is traditionally employed, and to achieve sufficient pressure buildup, this must be compensated for. Higher pressure could be achieved by reducing the radius or increasing the length of the nozzle throat, reducing the heating volume size, changing or increasing the amount of ablative material, or restricting the outward gas flow. Interruption experiments in air have been performed on four different model switch designs that are meant to highlight the possibilities and challenges of adapting self-blast technology to medium-voltage load current interruption. The results show that typical load currents can be interrupted at 24 kV, but below a certain critical current, in the present case 200 A, interruptions fail. Self-blast technology could prove useful in medium-voltage load current interruption in the future, provided a method for interrupting the lowest currents can be found. [ABSTRACT FROM AUTHOR]

Due to the high global warming potential (GWP) of SF6, the use of new gases in electrical equipment has drawn increasing attention. Here, the application of environmental‐friendly gas dodecafluoro‐2‐methylpentan‐3‐one (C6F12O) and CO2 mixture in 10 kV medium‐voltage switchgear is studied. First, the basic physical and chemical properties of C6F12O were discussed, and the toxicity and safety of its application in equipment was analysed. Then, the breakdown voltage was measured in the laboratory. The power‐frequency breakdown test was carried out with the mixing ratio of 2, 4 and 6% at 0.1∼0.2 MPa, and the influence of utilisation coefficient of electric field on the breakdown performance was analysed. Finally, the appropriate mixing ratio was determined and tested in the load switch cabinet and the circuit breaker switch cabinet, including the power frequency withstand voltage test and the lightning impulse test. The test results show that 4% C6F12O and CO2 meet the standard value tested at a pressure of >0.14 MPa, which has the potential to be used as an insulating gas in a 10 kV switchgear. [ABSTRACT FROM AUTHOR]

This study proposes a fault diagnosis method for extracting and classifying the fault features of switchgears in accordance with the monitoring data of three‐phase voltage and current, temperature, humidity, and flashing from the smart breaker and sensors. The fault features are calculated using multivariate multiscale sample entropy (MMSE) for the data mining of multivariate monitoring process. The similarity measure of the composite delay vectors of multivariate time series in MMSE is improved by introducing a cloud model to soften the similar tolerance criterion. The modified MMSE is defined as multivariate multiscale cloud sample entropy (MMCSE). The MMCSE features of switchgear monitoring data can be achieved in different time scales in describing various switchgear faults. Subsequently, a classification method based on fuzzy support vector machine (FSVM) is further adopted to identify different types of switchgear faults using the MMCSE features. In addition, a dropping semi‐normal membership cloud model is applied to modify the uncertainty quantification of the relationship among fault samples in FSVM. The effectiveness of the proposed method is validated with the monitoring data in a 10 kV switchboard. [ABSTRACT FROM AUTHOR]

Abstract The failure analysis for each component is the biggest problem for maintenance task for switchgears. It should consider the redundant mechanical and electrical systems, in circuit breakers for the analysis. In recently researches, they are often described innumerable system failure modes, according to the methodology applied: RCM plus, RCM 2, among others. Nevertheless, in these methodologies, the specific effects are independently considered (for example the IEEE standard) has proposed 11 failures modes, furthermore CIGRE has proposed 4 evolutionary failures modes however The effects are independent for the failure mode, there is no interaction between them. On the other hand, this research proposes a new perspective with combinations between them and the degradation sequence for ageing process. A proficient method is used to recognize main failure modes, according to IEC 62271–100 (2011) and IEC 62271-1 (2007), later, in the space of arbitrary components, it accomplishes system reliability analysis to calculate the system failure probability, due to reliability analysis, this research proposes a new proposal to complement the IEC standards. To establish the main failure and to propose in decreasing in order their influence. This new proposal to model the searching technique uses the Weibull and gamma distribution. Finally, the authors have done a case study with the new proposal, to prove the reliability goal for contending failure modes under the faster circumstances than traditional methods. In the section 1, the main aspect for the failure analysis in switchgear is described, in the section 2 a system reliability is analyzed with the failure modes criteria: A classical approach and a reliability scope in the analysis. In the section 3 a new proposal is described for a framework, it considers the failure mode analysis and reliability studies, later, in the section 4, the case study is developed with thirty-four hydraulic switchgear and 3201 site acceptance test for preventive maintenance and a section 5, for a discussion about the new proposal in the international standards. Highlights • This research proposes a reliability model for circuit breakers. • The Classical and Bayesian methodologies has been considered for ageing degradation. • The case study for 3201 test and 34 switchgear are developed for the validation. [ABSTRACT FROM AUTHOR]

Arc chutes comprising ferromagnetic splitter plates are common in SF6-insulated medium-voltage switchgears. By splitting and cooling the electric arc, they help to interrupt moderate currents such as the rated current in load break switches or the transfer current in switch–fuse combinations. Between the splitter plates of such an arc chute, the motion of the arc depends on the balance of the attracting magnetic forces from the ferromagnetic plates, the repelling forces between two arc columns at the two sides of a plate, and the viscous forces from the insulating gas. We simulated this motion by calculating the magnetic forces acting on the arc columns after splitting by means of 2-D and 3-D electromagnetic finite-element analyses and by taking the viscous force as drag force into account. This paper describes this calculation method and compares the simulation results with those of laboratory tests. [ABSTRACT FROM AUTHOR]

Liquid nitrogen (LN2) is one of the most effective insulation medium for the realization of a new and environment friendly power switchgear system. This novel power switchgear will be a promising alternative to the gas insulated switchgear system. Preliminary study about arc phenomenon is very important for the future design of this novel approach. The fundamental research on high-density arcs was demonstrated using LN2 for the very first time and some important first-hand investigations were previously observed. These investigations were based on electrodes that were geometrically symmetrical. The thorough study of arc behavior in LN2, also demands the asymmetrical analysis be done in the same manner. These new results would further enrich our understanding of arcs in LN2 and would be helpful for the future design of liquid nitrogen insulated metal enclosed switchgear (LNIS). The objective of this research is to study the arcing behavior in LN2 using asymmetrical electrodes. The research investigates the arcing times, arc energies, LN2 consumption rates, temperature difference after arc occurrence, and surface erosion of the electrodes due to arcing. Experiments were done at four different dc voltage levels (i.e., 200–500, with a 100 V step) and arcs were intentionally created on asymmetrical electrodes with different electrode arrangements and materials, respectively. The geometrical arrangements for the experiments are sphere-plane and rod-plane, whereas the electrode materials are aluminum alloy (Al6061), pure copper (Cu), and stainless used steel (SUS) type, respectively. Arcing times, residual voltages, arc voltages, and arc currents were measured using different apparatuses. The results are quite in agreement with the previous investigations done by the first author. LN2 has the shortest arcing time in comparison to air insulation and sphere-plane quenches arcs quicker than rod-plane type electrodes in most of the cases. It was also observed that LN2 consumption due to arcing is quite lower even at heavy interrupting currents and overall difference in temperature due to arcing is approximately zero when the volume of LN2 is more than 100 L. [ABSTRACT FROM AUTHOR]

Solid insulated switchgear (SIS) has been developed as a substitution for sulfur hexafluoride gas insulated switchgears in the medium voltage class. Its main circuit including a vacuum interrupter is coated with epoxy resin. An embedded electrode was employed in order to enhance the surface insulation performance for further miniaturization and higher stress design. In the previous studies, the surface insulation performance was examined by using a model electrode system which modified the electrode system of the moving part of SIS and the estimation method of the surface breakdown voltage was proposed. In addition, the simulation of the surface breakdown characteristics of a model electrode system was conducted and a design method was proposed. In the present study, the insulation performance of the solid part was taken into account and the insulation design was conducted using the proposed design method. The "equivalent insulation distance" was introduced and the partial discharge inception field strength was also taken into account. The insulation design was done for 22, 33 and 77 kV systems and the values of the design parameters were provided. In addition, it was found that two different types of the design concepts were available. [ABSTRACT FROM AUTHOR]

Partial discharge accelerates insulation aging and leads to insulation failure of high voltage equipment． PD test is an important basis for condition evaluation of switchgear． It is usually combined with transient earth voltage and ultrasonic detection methods to detect partial discharge of switchgear，which is vulnerable to external signal interference and difficult to locate the fault． Therefore，based on the formation mechanism of transient earth voltage，this paper analyzes the characteristics of transient earth voltage and proposes a long － term monitoring method for suspicious HV switchgear． The antenna is used to shield the external interference signal，and the switchgear partial discharge signal is identified from complex signal sources，Finally the fault location of partial discharge can be located by the method of matrix probe． The fault location is found and located in the actual working case，which can verify the method is accurate and feasible． [ABSTRACT FROM AUTHOR]

Future multi-terminal dc networks are envisioned for the large-scale integration of renewable energy sources into today's power systems. An essential aspect for the reliable operation of these systems is the fast and selective dc-side fault handling and separation of faulted lines. The objective of this paper is the development and evaluation of a multi-terminal dc protection strategy based on fault-blocking converters (e.g., full-bridge based modular multi-level converters) and high-speed switches. Both a suitable fault control and a new high-speed switch design for a fast separation of faulted dc lines are elaborated. The novel concept is intended to reduce the requirements on the high-speed switches compared to dc circuit breakers and to ensure a fast restoration of the active power transmission capability, as well as the dc voltage. The fault-clearing strategy is analyzed using electromagnetic transient (EMT) simulations under variation of the fault location, type, and resistance. The investigations are carried out in a cable-based multi-terminal HVdc system with full-bridge modular multi-level converters in symmetrical monopole configuration. [ABSTRACT FROM AUTHOR]

Renforth et al. in 2017 present a novel online partial discharge (OLPD) high-voltage (HV) insulation condition monitoring (CM) solution to monitor complete HV networks in petrochemical and other critical industry facilities. Continuous, 24/7 OLPD insulation monitoring of in-service cables, switchgear, transformers, and rotating machines operating at 3000 V and above provides operators with an early warning against incipient HV insulation faults that manifest themselves through high PD activity. Knowledge of the type, severity, and source of any site(s) of PD across the HV network (including remotely connected plant such as Ex/ATEX HV motors located in hazardous gas zones) enables pinpointed preventative maintenance interventions to be made to the HV insulation system during planned maintenance turnarounds to avoid unplanned outages. To monitor a complete HV network, OLPD sensors and monitoring nodes are distributed at strategic locations across the network. The CM data from the distributed nodes are passed via Ethernet/LAN to a partial discharge monitoring server (PDMS) located at the control center of the facility with a secure internet connection. The PDMS operates an advanced OLPD monitoring database for the logging, display, benchmarking, trending, and visualization of the PD monitoring data on a graphical user interface. The insulation condition criticality (from 0% to 100%) of each phase of all of the individual HV plant items monitored is presented on a series of mimic screens of the HV network single-line diagram. This paper concludes with a case study of a complete HV network OLPD monitoring design solution implemented at a large, crude-oil processing facility in Eurasia. [ABSTRACT FROM AUTHOR]

When the pressure and temperature of a fluid exceed a critical point, the fluid enters into the supercritical (SC) region. In this region, the physical properties are believed to be in favor of a good current interruption medium. This paper focuses on the arc voltage characteristics of nitrogen arcs burning inside cylindrical tubes at different filling pressures: 1, 20, 40, and 80 bar, thus covering the SC region. Two different tube materials have been used in the experiments, alumina and polytetrafluoroethylene. Arc voltages are measured for arcs burning inside tubes of 2, 4, 8, and 15 mm inner diameters. In addition, free-burning arcs have been investigated at the same filling pressures. The arc current was 150 A at 350 Hz throughout the study. The arc voltage is found to increase with decreasing inner diameter of the tube at atmospheric pressure. At higher filling pressures (i.e., 20, 40, and 80 bar), however, such a simple relationship is not observed. The arc temperature and radius have been calculated based on the “simple theory of free-burning arcs” and the “two-zone ablation arc model.” The calculated arc radius decreases with increasing gas pressure. Furthermore, due to increased absorption of radiation at high filling pressures, ablation is found less significant for ultrahigh-pressure nitrogen arcs compared to atmospheric pressure arcs. This is in line with the observations from optical micrographs of the inner surfaces of the tubes exposed to arcs at different filling pressures. [ABSTRACT FROM AUTHOR]

The expected abolishment of SF6-gas in medium-voltage switchgear has prompted a search for replacements for the switch types that depend on SF6 to obtain the required capability, reliability, compactness, and cost. Ablation of polymers can enhance the arc-quenching capabilities in certain electrical switch designs. Several aspects, like electric arc plasma composition, gas flow, and wall stabilization, must play together to obtain successful interruption. In this paper, open and closed switch geometries and two nozzle materials [polypropylene (PP) and polytetrafluoroethylene (PTFE)] are studied in medium-voltage interruption experiments. Fundamental differences in the arc-quenching process for PP and PTFE are shown. In the case of PTFE, the current interruption performance depends on gas flow resulting from the pressure built up under the high-current period. In the case of PP, the gas flow plays a lesser role for the arc-quenching capability as the interruption capability is large even in an open design with no forced gas flow around current zero. Current chopping happens a few tens of microseconds before voltage zero crossing; thereafter, a remnant conductance in the contact gap is observed, lasting for up to several milliseconds. This can be explained by an arc-to-glow transition in the presence of hydrogen. [ABSTRACT FROM AUTHOR]

Charge generation in gas-insulated high-voltage direct current (HVDC) equipment has been investigated since surface charge accumulation was detected as the main challenge to insulation coordination. Over the years, researchers have made enormous progress using continuous ion current measurements or surface charging experiments with model spacers downscaled from gas-insulated components. Whereas the low sensitivity of the former method limits its measurement range, the latter method is timeconsuming and demands comprehensive modeling. In this paper, more than 3,000 hours of surface charge measurements are presented, covering the full range of charge generation processes from ion currents owing to natural ionization to the inception of micro-discharges. In accordance with gas-insulated equipment, Al2O3- filled epoxy resin was used for the solids, and sulfur hexafluoride (SF6) was used for the gaseous insulation. It has been demonstrated that the ion pair generation from natural ionization in the gas is significantly influenced by the surrounding solid materials, and therefore, scales with the insulation volume. From the onset of micro-discharges, sharp and locally limited charge patterns are formed, as surface conductivity does not appear to influence the investigated charge distributions. Whereas the primary charge dissipation from surface areas centered at the distribution could be explained in terms of the gas volume size, the discharge currents could not be reproduced with common ion-current models. At low electric fields, the observed charge decay indicates the presence of low-field conduction processes that cannot be explained by charge generation from natural ionization in the gas. [ABSTRACT FROM AUTHOR]

Air-insulated switchgear cabinets play a role in the protection and control of the modern power grid, and partial discharge (PD) switchgear is a long-term process in the non-normal operation of one of the situations; thus, condition monitoring of the switchgear is important. The air-insulated switchgear during PD enables the decomposition of air components, namely, O3 and NO. A set of experimental platforms was designed on the basis of the principle of ultraviolet differential optical absorption spectroscopy (UV-DOAS) to detect O3 and NO concentrations in air-insulated switchgear. Differential absorption algorithm and wavelet transform were used to extract effective absorption spectra; a linear relationship between O3 and NO concentrations and absorption spectrum data were established. O3 detection linearity was up to 0.9992 and the detection limit was at 3.76 ppm. NO detection linearity was up to 0.9990 and the detection limit was at 0.64 ppm. Results indicate that detection platform is suitable for detecting trace O3 and NO gases produced by PD of the air-insulated switchgear. [ABSTRACT FROM AUTHOR]

This study presents simulation and experimental verification of solid‐state switch overvoltage protection. The switching device is composed of two antiparallel connected forced commutated semiconductor valves and in analysed case has been used as a low‐voltage solid‐state bypass switch of UPS system. The aim is to identify the value of overvoltage induced on switch terminals and surge energy during an instance of current turn‐off in line with inductive impedance. Afterwards determine optimal solution that protects such a power electronics device. As a protection solution configurations and types of surge arresters have been examined. All simulations have been conducted using PSCAD software package on the model especially prepared for this purpose. [ABSTRACT FROM AUTHOR]

The usage of medium‐voltage switchgear is more and more common in high altitude areas. Few relative standards about the selection of switchgear air gap in low air pressure conditions are currently available for referring. In this study, four different types of switchgear air gaps, as well as a typical rod‐plane gap, are taken as the samples, and their positive and negative lightning strike discharge characteristics under low air pressure are tested in the artificial climate chamber. The effects of the electrode structure, polarity, air pressure, humidity, and gap distance on the discharge performances are analysed as well. Research results indicate that the four switchgear air gaps and typical rod‐plane gap differs greatly in lightning impulse discharge performances and polarity effects. In low air pressure conditions, the lightning impulse breakdown voltage of either positive or negative polarity can be corrected by U50 = U50,0 × (P/P0)n. The discharge voltage under positive lightning impulse is more easily affected by air pressure than that under negative lightning impulse. Atmosphere humidity will cause dispersiveness of air‐gap lightning impulse discharge voltage, which performs to be non‐linear with a gap distance lower under 400 mm. Research results are referable for the design, selection and installation of medium‐voltage switchgear in high altitude areas. [ABSTRACT FROM AUTHOR]

Arc-resistant low/medium-voltage switchgear and motor controls continue to provide proven levels of additional personnel safety in most every petroleum and chemical facility. The IEEE and the International Electrotechnical Commission generated testing guides and standards for these products, which are open to some level of interpretation when applied to products other than traditional medium-voltage circuit breaker or fundamental motor controller structures for which the current available standards and guides were intended when they were initially written. All medium-voltage variable frequency drives, because of their inherent designs, require high volumes of cooling air, which pose a real challenge in regards to providing full arc-resistant capabilities and compliance to the present testing guides, procedures, and standards. This paper will deliver real solutions to this problem through the application of unique cooling processes, arc channeling technologies, structural enhancements, arc fault energy-limiting methodologies, and special application considerations when applying arc-resistant medium-voltage drives. [ABSTRACT FROM AUTHOR]

Switchgear is an important power system protection equipment. Internal overheating of high-current switchgear has become the most common problem in the power system. In this paper, two different methods of simulation model are adopted to study the temperature rise issues of the 12-kV medium voltage switchgear. First, the electromagnetic field is calculated by using ANSYS APDL, then coupling with fluid dynamics software CFX to give the temperature and flow field distribution of the switchgear. Second, FLUENT and Maxwell 3-D are used to get the temperature and flow field distribution. It can be proven that CFX simulation of flow field is more suitable for the complex models. In the meantime, it has huge differences with FLUENT software when the temperature rise of the switchgear is calculated. In this paper, the influences of inlet velocity, the number of ventilation holes, and their positions are further studied, which could provide theoretical guidance for reducing temperature rise of the switchgear. [ABSTRACT FROM PUBLISHER]

A supercritical (SC) fluid is formed when both pressure and temperature of a fluid exceed the critical point, where distinct gas and liquid phases no longer exist. SC fluids demonstrate combined properties of gas and liquid, which make them interesting to investigate them as an arc extinction medium. This paper focuses on the arc voltage characteristics of industrial grade nitrogen subjected to different filling pressures up to 98 bar including SC region. Pressure, arc duration, current, and distance dependence of the arc are investigated by arc voltage measurement. It has been found that arc voltage increases with filling pressure without any abrupt change during the transition from gas into the SC region. Arc duration and current dependence of the arc voltage are not significant in the investigated parameter range. Arc voltage measurement with different electrode gaps suggests that the electrode voltage drop does not vary with filling pressure. [ABSTRACT FROM AUTHOR]