Switching Ground Research Articles

Active arc suppression based MMC-HVDC DC fault adaptive reclosing

DC fault arcs continue to burn for a certain period under line residual energy (LRE) excitation, and existing DC fault reclosing has to wait for the DC arc to extinguish, resulting in a slow system recovery due to the long arc dissociation time. To address this problem, adaptive reclosing with active arc suppression (AAS) is proposed to speed up fault recovery. Firstly, a strategy is given for coordinating DC circuit breakers to quickly control the ground switch (GS) to switch between input and output states. Secondly, the positive effect of GS changing the line endpoint characteristics to achieve the AAS function on reducing the LRE content is revealed. In addition, a multiple AAS coordination method is given for different DC arc extinguishing speeds. Further, after each AAS, the voltage difference between permanent and non-permanent faults is mapped using the Pearson correlation coefficient to determine non-permanent faults. Compared with other typical reclosing, the proposed adaptive reclosing can actively shorten the arc dissociation time, reduce the power outage time to 13.5%–30%, which effectively improves the successful probability of fault reclosing, and prevents the MMC from restarting under non-permanent fault.

Performance of a novel DC-DC low voltage stress boost converter for fuel-cell vehicle

Air pollution, global warming, depletion of fossil fuels and the lack of access to them due to potential political conflicts are some of the challenges that have forced governments to take necessary measures to promote and invest in the development of electric vehicles (EVs). One of the most important parts of EVs is dc-dc converter. A novel step-up single-switch unidirectional topology for a dc-dc converter is proposed in this paper. Some of the advantages of the proposed topology are the use of single-switch, ground switching, low input current ripple, wide range of voltage gain (VG), high level of VG, low stress level for semiconductor components, low input current ripple, small number of semiconductor and passive elements, high efficiency, and no need for high frequency transformer or coupled inductors. Topology analysis is done in continuous current mode (CCM) and calculations related to efficiency and appropriate design are performed to select the converter parameter values. Also, the proposed topology is compared with other similar topologies to show its high performance and superiority. To confirm the theoretical basis, laboratory prototype waveforms are evaluated and an efficiency of 93.2% is obtained.

Structural models based on spectral graph theory for land-based digital communication networks

Problem statement. For the organization of digital communication networks in the range of meter and decimeter waves, as well as when providing communications based on them in hard-to-reach areas, problems arise related to maintaining the stability and continuity of information exchange between the switching nodes of the ground infrastructure. The existing approaches to solving these problems are based on the use of means of retransmission using radio relay stations and individual flight-lifting equipment. However, with limited deployment time, in emergency situations and when performing special tasks, these approaches are unacceptable for a number of objective reasons. Therefore, the search for ways to improve digital communication networks in the range of meter and decimeter waves is relevant and has important scientific and practical significance for ensuring the stability and continuity of information exchange by ground switching nodes in a given area. Purpose. To develop a structurally stable model of digital communication networks in the range of meter and decimeter waves based on a group of unmanned aerial vehicles, ensuring the organization of continuous information exchange of ground switching nodes in a given area for the required period of time. Results. Based on the results of the research, practical recommendations are formulated for their use to solve the problems of organization, restoration and redundancy, as well as the operational build-up of digital communication networks in the range of meter and decimeter waves for a given time interval in unfavorable operating conditions. The prospects for further research in the organization of the structural contour of the complex multi-circuit adaptation of digital communication networks for various purposes are determined. Practical significance. The results can be used by specialists in the field of satellite radio navigation in the development of local navigation systems.

Improved Quasi-Z-Source High Step-Up DC-DC Converter Based on Voltage-Doubler Topology.

The step-up DC-DC converter is widely used for applications such as IoT sensor nodes, energy harvesting, and photovoltaic (PV) systems. In this article, a new topological quasi-Z-source (QZ) high step-up DC-DC converter for the PV system is proposed. The topology of this converter is based on the voltage-doubler circuits. Compared with a conventional quasi-Z-source DC-DC converter, the proposed converter features low voltage ripple at the output, the use of a common ground switch, and low stress on circuit components. The new topology, named a low-side-drive quasi-Z-source boost converter (LQZC), consists of a flying capacitor (CF), the QZ network, two diodes, and a N-channel MOS switch. A 60 W laboratory prototype DC-DC converter achieved 94.9% power efficiency.

Research on measurement technology of action characteristics of double-ended grounding switch based on flexible sensing

In order to solve the problems of high voltage switches’ operation characteristic tests, such as no double end grounding measurement, the inconvenient opening of grounding switch, easy injury, and equipment damage due to induced high voltage, a new measurement method is proposed in this paper, which adopts frequency conversion technology, time coding technology, and contactless flexible sensor technology, which can accurately measure the action characteristics of high voltage switch equipment under the condition of double terminal grounding. This method can effectively reduce the influence of field measurement factors and improve the accuracy, safety, and convenience of field measurement of high voltage switch action characteristics.

A compact mesoband microwave radiation system.

A compact mesoband radiation system is designed and tested. The system is composed of a charging power supply, a Marx generator, a switched quarter-wavelength oscillator, and a circularly polarized patch antenna. The Marx generator outputs a fast high-voltage pulse with a rise time of 10ns and an amplitude of 100kV, which is used to charge the oscillator. The oscillator consists of a quarter-wavelength coaxial transmission line, a ring ground switch, and a coupler. It generates a mesoband oscillation pulse with a center frequency of 350MHz and a percentage bandwidth of 10%. The oscillation pulse is radiated by the circularly polarized patch antenna. The measured radiation factor is greater than 50kV, and the radiation waveform is consistent with the simulation waveform.

Electric field numerical analysis and structure optimization of grounding switch in GIS based on finite element analysis

The grounding switch is an important component to ensure safety on its GIS and maintenance personal. In this paper, the COMSOL Multiphysics software is used to carry out electrostatic field analysis on grounding switch in GIS by the finite element method. This study also did a lot of research including drawing 3D models of key parts, gridding division and post-processing the data of electric field. The field intensity distribution diagrams and the maximum value of field intensity concentration area of key insulation position at 1100kV and 500kV are obtained. The electric field intensity distribution of GIS near the static contactor of the grounding switch is discussed, and the design of appropriately increasing the radius of the conductor in the part the great abrasion is proposed, and it provides a theoretical basis for the electric field distribution of electrical equipment.

Environmental impact analysis of on-demand urban air mobility: A case study of the Tampa Bay Area

Urban Air Mobility (UAM) uses electric vertical take-off and landing (eVTOL) vehicles to provide an alternative way of transporting passengers in urban areas. This study proposes a method of comparing air pollutant emissions from using ground transportation versus switching to multimodal UAM, including greenhouse gases and other air pollutants (NO x , SO 2 , PM 2.5 ). A study by Wu and Zhang (2021) addressed planning questions regarding the optimal placement of vertiports and estimated diverted demand from ground transportation modes by combining network design and travel mode choice models. The proposed method is applied to the case study of Tampa Bay region. A sensitivity analysis was conducted to further evaluate the impacts. The study reveals that on-demand UAM (considering vertiport access and egress modes) generates more greenhouse gases and other air pollutants (except NO x ) in the case study region compared to ground transportation modes. The emissions depend on the structure of power production. A lower UAM service price and more vertiports will further increase emissions.

A PDE constrained optimization based approach to evaluate the effect of the floating conductor transmission lines

The floating potential induced by the parallel transmission line is an important factor for the insulation coordination and ground switch design. In the case of HVDC transmission lines, it is more complicated to predict the potential on the parallel floating conductors due to the occurrence of the ion flow field. In this paper, the original nonlinear problem is reformulated to a PDE constrained optimization problem and the floating potential is obtained by minimizing the accumulated charges on the floating conductors. The obvious merit of the proposed approach is that all the boundary conditions are explicitly satisfied. The proposed method is applied to investigate the effect of the space charge to the floating potential on the practical HVDC transmission lines. Numerical results show that the presence of the ion flow field significantly enhances the potential on the parallel transmission lines, which can be a reference for the future floating potential prediction.

The hidden dangers analysis of the control logic on HSGS switch in Guizhong station

Restricted by the Earthing electrode current, the metal return becomes the most commonly connection in converter stations after unipolar blockade or unipolar outage. Therefore, it is very important for the safety and stability of the whole HVDC system whether the switching operation between single-pole ground return and single-pole metal return is safe and stable. Combined with the interlock logic of HSGS switch (high speed grounding switch) in Guizhong Station and the simulation operation, this paper analyzes the operation sequence of metal return, and points out the interlocking logic provided by the DC station control system can not prevent the risk of DC unipole locking caused by human misoperation under specific conditions. In addition, according to the current topological relationship in the operation of metal return, this paper presents a scientific modification plan with electric quantity interlocking, which can prevent the operators from misoperation and provides reference for the interlocking logic to other HVDC transmission system.

Calculation and Structure Optimization of Electric Field Distribution of The 10kV Solid-sealed Polar Pole

As one of the core modules of the ring - net switch cabinet, the solid-sealed polar pole was used to seal the three-station isolation ground switch and vacuum arcing chamber together. The electric equipment was concentrated, which was prone to electric field distortion. In this paper, a three-dimensional simulation model was established based on the drawings of the solid-sealed polar pole. The electric field distribution under the initial structure was calculated based on the finite element method, and it was optimized by adjusting the thickness of the moving contact and epoxy layer, changing the radius of the metal pull rod in the control mechanism and adding the equalizing ring on the shell surface. The results showed that when the inner diameter of the moving contact was 20mm, the outer diameter of the air layer was 43mm, and the radius of the metal tie rod in the control mechanism was 18mm, the field intensity in the solid-sealed polar pole was relatively reasonable, but the maximum E-field intensity in the arc-extinguishing chamber gap between the contacts was up to 5041V/mm. It was necessary to carry out pressure withstand test to ensure insulation safety. The results of this paper could provide reference for the optimal design of the solid-sealed polar pole.

가스절연지상개폐기 PD 자동진단기법 연구

Partial discharge diagnosis is being carried out to prevent failure of ground switch of distribution facilities. However, the reliability of partial discharge diagnosis is insufficient because the results are different depending on how the experts classify the partial discharge and noise signals. Therefore, in this paper, a method to automatically classify partial discharge and noise signals was studied in order to improve the reliability of the partial discharge diagnosis results of ground switch. Partial discharge and noise signal are obtained through the High Frequency Current Transformer(HFCT). And the features were extracted based on the pulse shape analysis, the standard deviation and gravity center of signal. The features are used as input to neural networks and learned using back-propagation. In addition, the structure of neural networks was optimized through genetic algorithm.

Transformer Fuses—Mind the Gap

Fuses are commonly used to provide medium voltage (MV) protection to distribution transformers. Unfortunately, there are certain deficiencies introduced when primary-side fuses are used. In paper mill power systems, given the unique organization of the paper mill loads around individual feeders to facilitate load shedding, it may be advantageous to provide transformer differential relay protection from the primary of the transformer to the load side of the main secondary breaker instead of primary fuse protection. This protection can then trip either a primary-side grounding switch (with fuses) or a primary-side feeder circuit breaker using a fiber or a WiMAX (Worldwide Interoperability for Microwave Access) connection. Protection against overload is provided by a secondary main circuit breaker and by design.

A Compact Frequency Diversity Antenna with DGS and SRR Mode Switching for LTE and WLAN/WiMAX Wireless Systems

The integration of a compact antenna design with frequency diversity in a wireless system is challenging. In this work, a planar antenna using defective ground and coarse frequency switching with connected split ring resonator through PIN diodes are presented. The antenna design is based on connected radial stubs which form a circular patch. Slots in the bottom plane create a corrugation-like structure, and it results in the defective ground, which contributes to the localization of electric flux at the different area for multiband operation. The antenna was simulated and fabricated on a 1.6 mm thick FR-4 substrate. The coarse tuning of the frequency band is tested and compared with the simulation data. The measured results depict broadside radiation pattern at different frequency with a peak gain of 3.72 dBi. The compact size (45 × 45 mm2) and diversity frequency resonance in the antenna makes it suitable for LTE and WLAN/WiMAX application systems.

Research and Application on Design of Underground Container Logistics System Based on Autonomous Container Truck

In this paper, a kind of underground passage automated freight transport system based on the autonomous dual-mode container truck is proposed, and the overall structure of the automated freight transport system, the allocation of the transportation equipment, the comprehensive design of underground passage, the comprehensive analysis of transportation organization, the reasonable layout of the freight transport terminal, and the design of connection with the overall operation of the port are studied. Taking the connection passage between the central operation area and the eastern operation area of Yantian Port under planning and construction as an example, this paper expounds the application of the underground automatic freight transport system design method in the underground container logistics system within the port area. Based on the current situation and the long-term planning requirements of Yantian Port, the overall route of the connection passage between the central operation area and the eastern operation area is studied; the dual mode transportation organization model based on the combination of autonomous driving and manned driving is designed, and the manned driving mode shall be adopted within the operation area. In the connecting tunnel, there is the interference-free, fully-enclosed, line-fixed, and no man’s land application scenario, and the autonomous driving mode shall be adopted. The corresponding ground switching area is proposed to match the dual-mode transportation system of the autonomous dual-mode truck; such switching area is composed of the mode switching area, truck storage area, and driver rest and management room. Compared with the traditional tunnels, the autonomous freight transport passage has obvious advantages in saving project cost and improving transport efficiency.

Discussion on the method of measuring the loop resistance of high voltage circuit breaker by double-ended grounding technology

Loop resistance is an important technical indicator reflecting the performance and operating status of high-voltage circuit breakers. The traditional test method requires at least one side of the grounding switches of the circuit breaker be opened, and the field operation needs to wait for the dispatch approval, so the work efficiency is extremely low. According to the actual requirements of on-site measurement of high-voltage circuit breakers, a test method and test scheme have been proposed in this paper for measuring loop resistance by using the double-ended grounding technology. At the same time, according to the structural characteristics of high-voltage circuit breaker, the test deviation between the method and the traditional test method is analyzed and compared. Finally, it is concluded that the test method for measuring the loop resistance through using the double-ended grounding technology can fully meet the actual needs of the project.

Induced Voltage and Current Simulations, Safety Criterion, and Mitigation for EHV Transmission Lines in Close Proximity

One of the benefits of double-circuit transmission lines is that line maintenance work can be performed on a de-energized circuit while the other circuit remains energized. However, induced voltages and currents can be generated on the de-energized line due to electrostatic and/or electromagnetic coupling effects and the close proximity to energized conductors. In order to mitigate the safety concern related to high induced voltages or currents, line discharging grounding switches (LDGS) may be installed. Since this can be an expensive solution, the magnitude of induced voltage and current is the key for defining safety criteria to judge whether or not a costly mitigation plan is needed. This paper presents the theory of induced voltage and current and a sensitivity analysis of influential parameters that impact each. In addition, a safety criterion using arc reach calculation is proposed to determine when LDGS are required. A case study is included.

Influences of secondary arc-based grading capacitor of multi-break circuit breaker on the transient stability of power system

The grading capacitor (GC) of circuit breaker (CB) is one of the most cost-effective methods to suppress secondary arc. Taking the double-break CB as an example, its topology is briefly introduced. The electric circuit for power system with GC is then established. From the perspective of minimizing secondary arc current, the formula for the capacitance of GC is deduced according to the Kirchhoff's voltage law. Based on the equal-area criterion, the transient process of power angle and speed of generator in the event of fault is investigated, and the role of GC in the transient stability is quantitatively investigated. Meanwhile, the expressions for the accelerating and decelerating areas are computed through the numerical calculus, and the impact of GC capacitance on the critical clearing time (CCT) is discussed. Furthermore, to verify the aforementioned analysis, a model is established in the environment of MATLAB/Simulink, and two cases are considered, i.e., a single machine infinite bus (SMIB) power system and a multi-machine power system. Both the theoretical analysis and the simulation results demonstrate that the use of GC can strength the electrical connection between two remote power sources, undermines the oscillating amplitude of power angle, and shorten the attenuation duration. As a result, the CCT and transient margin would be increased. In other words, we can prong the dead time and guarantee the successfulness for autoreclosure scheme. The GC of CB is much superior to the existing four-legged shunt reactor and high speed grounding switch in addressing the secondary arc issue.

Research on Induced Voltage and Current for Hybrid Transmission System Composed of GIL and Overhead Line

Abstract Gas insulated metal-enclosed transmission line (GIL) is a substitute for overhead line, which is used for power transmitting in complicated geographical or geological environment In order to satisfying the requirements of operation in maintained state, each side of GIL needs to be installed a grounding switch. For the hybrid transmission system composed of GIL and double-circuit overhead line, the whole overhead line will be divided into incomplete transposed/non-transposed parts due to connection of GIL. When one of the grounding switches of GIL closes, it can lead to much greater induced current in each grounding switch. The induced voltage and current for hybrid transmission system will also change because of different parameters between GIL and overhead line. Calculation methods of induced voltage and current for hybrid transmission system with GIL are presented in this paper. Then, calculation conditions for hybrid transmission system are analyzed based on these evidences. Su-Tong GIL pipe gallery project is taken as an example for simulation in ATP/EMTP. Compared with traditional transmission system with overhead line, much higher performance requirements for grounding switches of Su-Tong GIL pipe gallery project are necessary, especially for induced current.

Modeling and Measurement of Ground Bounce Induced by High-Speed Output Buffer With On-Chip Low-Dropout (LDO) Regulator

This study proposes a model of ground bounce induced by a high-speed output buffer with on-chip low-dropout (LDO) regulator. When the output buffer operates with a high-speed clock, high output impedance of the pass transistor and low impedance of the on-chip decoupling capacitor at load enable the ground bounce calculation by only using the self-impedance of the off-chip ground network and switching current spectra. The accuracy of the proposed model is indirectly validated by measurement. Simulated ground bounce by using the proposed model shows very good correlation with the experimentally validated SPICE model.