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ObjectiveDyslipidemia is one of the major public health problems in China. It is characterized by multisystem dysregulation and inflammation, and oxidant/antioxidant balance has been suggested as an important factor for its initiation and progression. The objective of this study was to determine the relationship between prevalence of dyslipidemia and measured changes in the levels of proinflammatory cytokines (IL-6, TNF-a, and MCP-1), thiobarbituric acid-reactant substances (TBARS), and serum total antioxidant capacity (TAC) in serum samples.Study designA cross-sectional survey with a purposive sampling of 2,631 enrolled participants (age 18–85 years) was performed using the adult population of long-term residents of the municipality of east coast China in Fujian province between the years 2017 and 2019. Information on general health status, dyslipidemia prevalence, and selected mediators of inflammation was collected through a two-stage probability sampling design according to socioeconomic level, sex, and age.MethodsThe lipid profile was conducted by measuring the levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) with an autoanalyzer. Dyslipidemia was defined according to National Cholesterol Education Program Adult Treatment Panel III diagnostic criteria, and patients with it were identified by means of a computerized database. Serum parameters including IL-6/TNF-a/MCP-1, TBARS, and TAC were measured in three consecutive years. Familial history, education level, risk factors, etc. were determined. The association between dyslipidemia and serum parameters was explored using multivariable logistic regression models. Sociodemographic, age, and risk factors were also investigated among all participants.ResultsThe mean prevalence of various dyslipidemia in the population at baseline (2017) was as follows: dyslipidemias, 28.50%; hypercholesterolemia, 26.33%; high LDL-C, 26.10%; low HDL-C, 24.44%; and hypertriglyceridemia, 27.77%. A significant effect of aging was found among all male and female participants. The mean levels of serum Il-6/TNF-a/MCP-1 were significantly higher in all the types of dyslipidemia among male participants. Female participants with all types of dyslipidemia but low HDL-C showed an elevation of IL-6 and MCP-1 levels, and those with dyslipidemias and hypercholesterolemia presented higher levels of TNF-a compared to the normal participants. The oxidative stress marker TBARS increased among all types of dyslipidemia except hypertriglyceridemia. All participants with different types of dyslipidemia had a lower total antioxidant capacity. Correlation analysis showed that cytokines and TBARS were positively associated with age, obesity, and diabetes mellitus, but not sex, sedentary leisure lifestyle, hypertension, and CVD/CHD history. The activity of TAC was negatively associated with the above parameters.ConclusionsThe correlation between the prevalence of dyslipidemia and the modification of inflammation status was statistically significant. The levels of proinflammatory cytokines, oxidative stress, and antioxidant capacity in serum may reflect the severity of the lipid abnormalities. These promising results further warrant a thorough medical screening in enhanced anti-inflammatory and reduced oxidative stress to better diagnose and comprehensively treat dyslipidemia at an early stage.

Background The aim of this study was to evaluate the efficacy and safety of a novel self-expanding nitinol stent (Smartflex stent) in femoropopliteal artery obliterans disease. Methods From June 2016 to May 2019, patients with atherosclerotic occlusion disease of the superficial femoral and popliteal arteries using the Smartflex stents were retrospectively analyzed in our institution. Patients were monitored at 1, 3, 6, and 12 months and annually thereafter. The main characteristics of the diseased vessels, perioperative and follow-up outcome were evaluated. Kaplan-Meier method was used to assess patency rate and the rate of freedom from clinically driven target lesion revascularization (CD-TLR). Results A total of 50 limbs from 48 patients (mean age 69.4 ± 8.95 years; 38 men) were included. Eighty-eight Smartflex stents (1.76 stents per limb) were deployed successfully. Of the study patients, 82% had claudication (Rutherford III), 10% had rest pain (Rutherford IV), and 8% had tissue loss (Rutherford V). Trans-Atlantic Inter-Society Consensus II C and D lesions were 26% and 42%, respectively. The mean lesion length was 18.2 ± 8.5 cm and the mean stented length was 22.3 ± 9.9 cm. The average follow-up time was 16.4 ± 8.2 months. Of these lesions, 42 (94%) were chronic total occlusions and 16 (32%) were severely calcified. The primary patency rate at 1 year per Kaplan-Meier estimating, the rate of freedom from CD-TLR at 1 year, and the second patency rate was 83.3%, 88.1%, and 94%, respectively. Among them, 90% patients had improved ankle-brachial indexes (0.47 ± 0.13 before and 0.84 ± 0.16 after). No stent fractures and kinking were identified. Conclusions Stenting of the femoropopliteal artery diseases using the Smartflex stent appeared to be safe and effective. It performed well in long-segment and above knee joint lesions.

In a voltage-source converter dc grid, a dc fault current limiter (FCL) is a key apparatus. When faults occur, it is supposed to effectively and immediately suppress transient short-circuit current to protect other equipment, e.g., converters. Additionally, it is required to bring as little negative effect as possible under normal operation. Although the respective advantages are highlighted in different FCLs, one or two key disadvantages can significantly decrease the overall performance. In this article, a novel magnetic coupling FCL (MCFCL) is proposed and achieves a good balance among its advantages and disadvantages. An MCFCL consists of a mutual inductor and some power electronic switch modules. The mutual inductor metallic primary winding is connected in series to the transmission line and magnetically coupled with the secondary winding. The secondary side impedance is controlled by the power electronic switch modules. The novel 4-segment model is proposed to demonstrate the current-limiting physics, formulate the current-limiting effect, and support the design. One medium voltage (10 kV) case study is carried out based on the numerical simulation. The MCFCL shows a better current-suppressing effect and a lower impedance under normal operation than the benchmark Reactor FCL. Finally, this article is validated on a scaled-down experimental facility.

Hybrid dc circuit breakers (HCBs) usually require a large number of insulated-gate bipolar transistors (IGBTs) with high turn- off capability for series and parallel connections. This requirement entails excessive cost. Compared with IGBTs, integrated gate-commutated thyristors (IGCTs) are another kind of fully controlled power device with high surge current and voltage capability but are low cost. However, the weak turn- off capability of IGCTs hinders their application to high-powered HCBs. On the basis of the complementary advantages of IGBTs and IGCTs, this paper proposes a mixture solid-state switch (MSS) for HCBs that uses the switching action of several IGBTs to create a low-current condition that favors the turning off of large-scale series-connected IGCTs. The MSS topology can significantly reduce cost while maintaining the excellent performance of traditional solid-state switches. This study also introduces two different turn- off modes for MSS, namely, single oscillation and multiple oscillations. Finally, 25 kV/20 kA prototypes in both modes are developed to verify the effectiveness of the MSS topology.

High-voltage dc (HVdc) circuit breakers (CBs) are a key technology of multiterminal dc (MTdc) systems and grids. In this article, a state-of-the-art 500-kV hybrid CB (HCB) topology is proposed and compared with other existing HCB solutions. Implementing the topology includes three important components: a modular designed high-current bidirectional solid-state switch (SS), an ultrafast mechanical switch (MS) based on a Thomson (CCDC) equipment with no conduction loss, whose corresponding functional verification test results have been presented in detail. On this basis, the overall 500-kV HCB and a comprehensive experimental platform are developed. Detailed experiments, including 25-kA turn-off and reclosing experiments, are conducted. The HCB was found to be capable of breaking a 25-kA current in 2.7 ms with 800-kV overvoltage, which is on par with the level of leading CBs worldwide.

Different from the continuous-switching behavior of series power electronic devices in converters, the single-switching attribute of dc circuit breakers (DCBs) provides opportunities to integrate metal oxide varistors (MOVs), balancing circuits, and series power devices. This paper proposes a modular design methodology based on discrete MOVs of a DCB with series power electronic devices. The modular dc circuit breaker (MDCB) topology and voltage balance issues, the steep front effect and solution, and the design method are proposed and analyzed in this paper. Compared with the traditional DCB, the MDCB has a self-balancing ability, thereby removing the voltage-balancing circuit and reducing the number of series modules. The standard designed cell can be operated as an independent DCB or compose a high-voltage DCB in series flexibly, which decreases the difficulty of design and commission. Finally, a series experimental platform based on an insulated-gate commutated thyristor, an insulated-gate bipolar transistor, and an injection-enhanced gate transistor is built to verify the correctness and effectiveness of the proposed design methodology.

The no-load curve of the dielectric recovery strength of the ultra-fast mechanical vacuum switch (MVS) changing with time is the theoretical foundation to optimize the turn-off strategy of the hybrid direct current circuit breaker with load commutation switch. To avoid the shortcomings of the classic synthetic circuit, a novel test circuit is proposed to measure the no-load dielectric recovery curve of the MVS in this paper. In the test circuit, a succession of pulse voltages is automatically applied on the MVS, and multiple breakdowns of the MVS occur in one test. Therefore, the dielectric strength of the MVS at multiple time points is obtained, and the envelope of the applied voltage on the MVS during one test can describe the dielectric recovery curve of the MVS; as a result, the test workload could be reduced dramatically and the measurement is more authentic. By changing test conditions, including the rate of rise of the test voltage and the operating speed of the MVS, no-load dielectric recovery characteristics are studied. The research has shown that the dielectric recovery speed of the MVS is irrelative with the rate of rise of the test voltage and it is directly proportional to the opening speed of the MVS.

Dynamic contact resistance measurement (DRM) is an effective technique to evaluate the contact condition in substations without dismantling circuit breakers. However, performing DRM tests with unsuitable test parameters will cause low repeatability of the test results, and even lead to the misdiagnosis of contact condition. Performing the DRM tests at high DC injected current can improve the repeatability. This paper studies the mechanism of the DC injected current on the repeatability of the DRM test results, and it also promotes a new determination method of the DC injected current amplitude. The impact of the DC injected current on DRM test results is reviewed. The mechanism of the DC injected current on DRM test results is investigated by analysing the chemical composition of the contact surface, the force exerted on the contacts, and the temperatures of a-spots on the contacts’ surface. Results indicate that not the Lorentz force, but the temperature of a-spots is the primary influencing factor. The amplitude of the DC injected current can be determined by calculating the temperatures of the a-spot on the contacts’ surface. And this method can also be used for other SF6 circuit breakers.

The direct-current (dc) fault-clearance capability of the modular multilevel converter (MMC) is a key issue for overhead line applications of voltage source converter-based high-voltage dc (VSC-HVDC) transmission systems. An MMC integrated with a dc circuit breaker (IDCB-MMC) is proposed to provide a cost-effective DC fault clearance and isolation solution. A mechanical switch (MS) and a load commutation switch are connected in series as the main branch of the dc circuit breaker. DC fault currents can be forced to transfer to converter- and line-side energy absorbing branches when submodule bypass protection and dc circuit breaker interrupting operations are coordinated. Therefore, the bulky and costly solid-state branch that uses numerous semiconductor devices and surge arresters can be eliminated. The dc fault clearance and isolation capability of the IDCB-MMC were verified through the simulation results for one pole of a 1000 MW/±320 kV VSC-HVDC system. Compared with an MMC that uses half-bridge SMs, the IDCB-MMC only requires few additional capacitors and switching devices and a simple MS, thereby resulting in several advantages, such as low cost, footprint requirements, and additional conduction losses.

Current commutation from the load current path to the commutation path is the precondition to interrupt current successfully for hybrid direct current circuit breakers (DCCB). With remarkable current commutation performance, current commutation drive circuit (CCDC), mainly consisting of air-core transformer, fast-closing switch (FCS), and precharged capacitor, is proposed by us. In this paper, to eliminate the operating losses of CCDC and to avoid unrecoverable damage of FCS, CCDC used in hybrid DCCB for current commutation has been improved. Different submodules (SM) of commutation path in hybrid DCCB are analyzed, and experiments have been carried out on a hybrid DCCB prototype. Theoretical analysis and experiment results have shown that no matter which kind of SM is used, improved CCDC can ensure reliable current commutation in hybrid DCCB. In the end, by taking total cost of CCDC into consideration, a novel optimization method is proposed to design the parameters of CCDC. With this optimization method, CCDC for hybrid DCCBs with different rated voltage and current can be designed individually and its cost could be reduced significantly.

DC grids, including highvoltage dc (HVdc) transmissions, midvoltage dc (MVdc) distributions, and low-voltage dc (LVdc) supply systems, have elicited widespread concern and rapidly developed in recent years [1]-[6]. Voltage and power can be flexibly controlled because power electronic equipment is widely used in dc grids. Moreover, the conversion stage for energy storage and renewable energy systems in dc grids can be simplified. Such simplification can reduce cost, enhance power conversion efficiency, and improve power quality.

As power semiconductor devices are the key components of hybrid DC circuit breakers (HCBs), how to select suitable devices is critical for the whole HCB design. First, this paper compared the general characteristics of press pack insulated gate bipolar transistor (IGBT), injection-enhanced gate transistor (IEGT), and integrated gate commutated thyristor (IGCT). Then working conditions of devices were analyzed from the perspective of HCBs. According to these, vital features of devices including maximum turn-off current, on-state voltage, conduction ability, and robustness of power semiconductor devices were carefully analyzed and compared. Related experiments were implemented to compare maximum turn-off capability, and the 4.5 kV/3 kA IGBT/IEGT was able to turn off 19 and 22 kA respectively after 5-ms current conduction. Analysis and experiments indicated that IGCT was suitable for natural commutation low-voltage and low-current hybrid circuit breakers, due to its low on-state voltage and huge surge current conduction ability. Comparatively, IGBT and IEGT were more suitable for very high current interruption, and IEGT was the superior selection among available commercial devices. However, the interference should be considered in applications.

With rated voltage of multi-terminal direct current (MTDC) power transmission system varying from ±160 kV to ±500 kV and even ±800 kV, high-voltage direct current circuit breaker (DCCB) is in urgent demand. With remarkable features of low operating losses, free-maintenance, and relative small investment, DCCBs based on mechanical vacuum switch (MVS) and current commutation drive circuit (CCDC) are recognized to have bright prospects in practical engineering. However, parameters design and serial topology selection for high-voltage mechanical DCCB with CCDC are still open problems. Motived by this, parameter design method for a modularized DCCB with CCDC is proposed. Then, parameters of 500 kV DCCBs with two typical serial topologies, namely, modularized serial topology and integrated serial topology, are optimized, and simulations are conducted in PSCAD/EMTDC for verification. In the end, performances of the two serial topologies, including dynamic voltage balancing, fault-tolerance capability and cost, are discussed. According to research results, modularized design methodology is recommended for high-voltage DCCB with CCDC.

To investigate the effect of weld induced residual stresses on the crack performance, standard compact tension specimens were cut into two pieces, then joined to form welded specimens under various welding conditions. The crack opening displacement was measured by digital image correlation technique. It is found that specimens welded in the opposite direction show smaller crack opening displacement than those welded in the same direction. The crack opening displacement decreased as the distance from the crack tip to the center of weld line was increased from 8 mm to 30 mm. The crack opening displacement of the specimens with 30-minute time interval was lower than that of the specimens without interval, regardless of welding directions.

The fast mechanical switch equipped with the Thomson-coil actuator is one of the key devices in hybrid HVDC circuit breaker. And electromagnetic damping technology can solve the problems of high-speed damping operation without adding additional mechanical parts. In order to make the opening/closing operation process as unified as possible, the driving and damping voltages are the same in the previous research. In this paper, the effects of different combinations of driving and damping voltages on the travel characteristics have been studied. Voltage combinations are divided into three types. The first type is to change the driving and damping voltage at the same time; the second is to keep the damping voltage constant and change the driving voltage; the last type is to keep the driving voltage constant and change the damping voltage. In order to ensure that the contacts system can move to the isolating distance in 3 ms, the driving voltage should not be reduced. At the same time, in order to ensure a better damping effect, the buffer start time range should be as large as possible. Therefore, it is suggested that the damping voltage is 2%–4% lower than the driving voltage. A fast simulation method based on equivalent circuit method, which avoids lots of test operations, has been proposed in this paper. It can provide reliable references for the application and improve the feasibility and reliability of fast mechanical switch in engineering.

In order to improve the working characteristics of high-voltage circuit breakers and achieve energy saving and emission reduction, a new operating mechanism of 126kV high-voltage vacuum circuit breaker directly driven by three-phase permanent magnet synchronous motor (PMSM) was studied. The simulation model of the control system was established by Matlab/Simulink, and the control system of the direct drive operation mechanism of the vacuum circuit breaker was designed and implemented based on the TMS320F28335 hardware platform. The simulation calculation and experimental results show that the 126kV high-voltage vacuum circuit breaker operating mechanism directly driven by PMSM can realize the opening and closing operation of the circuit breaker according to the preset contact motion curve. The research shows the feasibility of using a motor to drive the 126kV high-voltage vacuum circuit breaker operating mechanism, and can meet the requirements of high-voltage circuit breaker operation.

Whether fault current can be broken quickly and reliably depends on dynamic characteristics of LC resonant commutation branch of mechanical DC circuit breaker.Thereby, the breaking characteristics of mechanical DC circuit breaker based on LC resonant commutation are studied in this paper. The topological structure and action time sequence of mechanical DC circuit breaker based on LC resonant commutation are introduced firstly. Transient voltage and transient current equations of mechanical DC circuit breaker based on LC resonant commutation are deduced on the basis. The influence of fast mechanical switch contact gap, resonant capacitor C, charging voltage of resonant capacitor C, resonant inductance L, solid-state switch turn-on time and other parameters on fault current, breaking time and other breaking characteristics are studied finally, thereby providing feasibility basis for parameter design of LC resonant commutation branch.

Motor drive operation mechanism of High-Voltage Circuit Breaker(HVCB) need permanent magnet synchronous motor(PMSM) with high-dynamic response. Reducing the rotor inertia of PMSM is one technique to realize high dynamic response of the motor. By digging holes in the rotor, the inertia can be reduced. The influence of shape, position and size of inertia-reducing holes on the performance of PMSM is analyzed by using Ansoft. The optimized design of a given PMSM is presented in this paper. The rotor inertia is reduced by 10% after optimization.

A DC circuit breaker is piece of core equipment for DC grid construction and can achieve fast isolation of DC faults in the grid. In this paper, based on the fault characteristics and protection requirements of an AC/DC hybrid distribution network, the technical parameters and topology structure of an inductance and capacitance (LC) resonant commutation-type mechanical DC breaker are proposed. Furthermore, an engineering prototype of the mechanical DC circuit breaker is developed, then a small current breaking test and a large current breaking test are carried out. The test results show that a 10 kA fault current can be interrupted within 10 ms by the engineering prototype. Finally, the engineering prototype of the mechanical DC circuit breaker is installed in the AC/DC hybrid distribution network project, and a current breaking test is carried out. The test results show that the mechanical DC circuit breaker has good running conditions, and the function and performance meet the engineering design and operation requirements.

With the rapid development of multiterminal direct current (MTDC) grids, high-voltage direct current circuit breakers (HV-DCCB) capable of interrupting currents within 5 ms are in urgent demand. The mechanical DCCB has always been one of the main proposals for HV-DCCBs. The current commutation is the prerequisite for mechanical DCCBs to interrupt currents successfully. Focused on the current commutation difficulty, a novel mechanical DCCB has been investigated in this paper. A simulation model of the novel mechanical DCCB in MTDC system for fault current interruption was established in PSCAD. By analyzing the simulation results, the detailed transient varying patterns of current, voltage, and energy in the novel mechanical DCCB during its interruption process are revealed. To verify the feasibility of the novel mechanical DCCB, a prototype was developed in the lab, and current interruption tests were carried out on the prototype. Experimental results have shown that a current of 5.3 kA can be interrupted by the prototype within 3 ms. In the end, failures that occurred in initial experiments are discussed and relative protection measures have been proposed. By adopting these measures, failures are successfully avoided and the normal operation of the novel mechanical DCCB are ensured.

A large and high-quality single crystal (Li0.84Fe0.16)OHFe0.98Se, the optimal superconductor of newly reported (Li1-xFex)OHFe1-ySe system, has been successfully synthesized via a hydrothermal ion-exchange technique. The superconducting transition temperature (Tc) of 42 K is determined by magnetic susceptibility and electric resistivity measurements, and the zero-temperature upper critical magnetic fields are evaluated as 79 and 313 Tesla for the field along the c-axis and the ab-plane, respectively. The ratio of out-of-plane to in-plane electric resistivity,\r{ho}c/\r{ho}ab, is found to increases with decreasing temperature and to reach a high value of 2500 at 50 K, with an evident kink occurring at a characteristic temperature T*=120 K. The negative in-plane Hall coefficient indicates that electron carriers dominate in the charge transport, and the hole contribution is significantly reduced as the temperature is lowered to approach T*. From T* down to Tc, we observe the linear temperature dependences of the in-plane electric resistivity and the magnetic susceptibility for the FeSe layers. Our findings thus reveal that the normal state of (Li0.84Fe0.16)OHFe0.98Se becomes highly two-dimensional and anomalous prior to the superconducting transition, providing a new insight into the mechanism of high-Tc superconductivity., Comment: 11 pages, 4 figures, supplementary information is not uploaded

This paper summarizes the developing autonomous maintenance support system in 4m×3m WT, describes in detail the project implementation, the main advanced points, effects and application situation, the use of funds, documents archived situation and so on. The application results through the serial tests show that the developed system has successfully achieved the expected targets and has forecast, efficient, economical merit about the test equipments maintenance.

In order to meet the increasing requirement of modularization and interconnection for the high voltage switchboard monitoring systems, this dissertation introduced an online monitoring system based on the embedded system. The system adopts DSP as its kernel data processing unit and an embedded microprocessor as its kernel system configuration and communication unit. The object-oriented method was also used in the software development. By integrating all these methods we made a monitoring system which is highly modularized and easy to communicate with the substation through LAN.

Owing to the lack of sufficient power loss data of different working conditions for GTO in the technical manuals of many companies, the manufactures and the consumers often encounter difficulties in selecting suitable devices for the design of practicable application systems. The authors have constructed a large capacity test circuit to carry out experimental investigation on the loss characteristics of GTO under various arrangements of circuit parameters. Then the powerful ANN (artificial neural network) and the BP (backpropagation) algorithm are introduced to build up the quantitative relations between the varied circuit parameters and the recorded loss data so that power loss tables can be created. In addition, the paper poses a revised steepest algorithm to fit the high-order heat transfer model of GTO according to its transient thermal behavior. All the algorithms are integrated in a software package based on which to carry through power loss analysis and output the transient and average junction temperature data or curves.