Search

Different from typical circuit breakers, breakers used to switch AC filters in convertor stations have to operate frequently according to the real-time operation mode and daily load changes. Therefore, the performance of filter breakers decreases very quickly, which leads to frequent accidents. Both preinsertion resistors and controlled switching devices can suppress switching transients. In this paper, a comparative analysis of whether a controlled switching device and preinsertion resistor should be adopted is carried out using PSCAD. The transient is calculated as the combined result of the switching angle and preinsertion resistor value, and the optimal configurations are proposed. After determining the resistor value and whether a controlled switching device should be included, the reference voltage of the arrester should be reevaluated.

The Solid-State direct current (DC) circuit breaker (SSCB) is a key equipment to ensure the safe and reliable operation of medium-voltage DC (MVDC) distribution networks. A distribution network solid-state DC circuit breaker with current-limiting function (CLSSCB) topology is proposed in this paper. The CLSSCB adds current-limiting circuit and continuous current branch on the basis of traditional SSCB. The current limiting circuit can significantly reduce the rise rate and peak value of the fault current by using auxiliary current limiting reactance and current limiting impedance. The continuous current branch uses the freewheeling diode to reduce the energy absorption of the non-fault side arrester and effectively shorten the fault clearing time through the input of the freewheeling resistance. In this paper, the working principle of CLSSCB is analyzed in detail and theoretically deduced, and the selection method of key device parameters of CLSSCB is given. The CLSSCB simulation experimental model based on the PSCAD/ EMTDC software is built, and the feasibility and effectiveness of the proposed scheme are verified in the single-end and two-end DC distribution network scenarios, respectively.

Ensuring thermal stability is an important aspect of an arrester design process. In this paper, the thermal stability of station class surge arresters is investigated using a coupled electrothermal numerical model. An ungraded 550-kV-station class arrester model is successfully validated against temperature measurements in power grid operation. The arrester cooling rate is introduced to determine the thermal stability threshold. Thermally stable and unstable scenarios are compared. The influence of selected arrester design parameters on the stability threshold is analyzed. It is shown that an improved heat transfer in the arrester air gap increases the thermal stability threshold significantly. Additionally, the nonlinear zinc oxide material characteristics influence the thermal stability threshold strongly. Furthermore, a thermal stability prediction approach based on few, computationally less expensive simulations is proposed. Finally, the results are confirmed for an arrester model that is equipped with a field-grading system. The paper shows that the presented field simulation approach can be reliably used to determine the stability threshold of an arrester, thus, reducing the need for costly laboratory tests.

Accurate evaluating the lightning induced voltages of distributed networks has been the subject for several decades. The technique on the interface between the field-to-line coupling model and power system simulators are of particular interest. In this article, a solution of the Agrawal's field-to-line coupling model is derived and an easy-to-implement macro-model is developed. Combining with the “Frequency Dependent (Phase) Model” component included in PSCAD, the proposed macro-model can be directly integrated into PSCAD to evaluate the lightning induced voltages on the overhead lines. The validity and efficiency of the proposed method is demonstrated by several examples. Finally, a 1-km 35 kV overhead line above an imperfectly conducting ground is studied, and the influences of the metal-oxide arrester to the lightning induced voltages are discussed.

This paper studies the AC pollution breakdown characteristics of the EGLA and broaden current knowledge of pollution flashover. Compared with the flashover of the normal insulator, three kinds of specificity of the EGLA were found. Firstly, the pollution flashover process can be divided into three categories. Secondly, the wet flashover voltage, Uf _wet, of the novel insulator is higher than the dry flashover voltage, Uf _dry. Thirdly, the piecewise fitting methods with aESDD^-b+d and aESDD^-b+ cESDD^-d are more suitable for fitting the empirical formula of flashover voltage. Furthermore, to explain specificity, the electric potential and electric field distribution are calculated based on the finite element method. Calculated results indicate that when the EGLA is covered with a 0.5mm water film, the maximum electric field intensity decreased from 2.17 kV/cm to 1.99 kV/cm. Also, U_arrester (the withstand voltage of the insulation section) was obtained from the tests and it presents a discontinuous and random increasing trend until flashover occurs, which is considered to be one of the important reasons for the specificity. Besides, based on the Obenaus model and Hampton's criterion, we further analyzed the arc development process by a simplified plate model

Hybrid circuit breakers (CBs) are the most promising technology to isolate DC faults in modular multilevel converter (MMC)‐based DC grids. However, they consist of expensive power electronic components that are sensitive to high overvoltage and overcurrent. This study proposes a hybrid high‐voltage DC circuit breaker with an energy absorption branch of a parallel arrester structure, and investigates the possibility of reducing the fault current and the switching overvoltage. First, the basic principle of an energy absorption branch with a parallel arrester structure is presented. Then, the simultaneous and sequential insertion strategies are illustrated. Second, each strategy and each structure are combined separately to analyse their respective characteristics in reducing the overvoltage, the fault current, the energy absorption and the fault clearance time. The sequential insertion strategy of the proposed energy absorption branch is proved to have the best performance. Finally, the trade‐offs between these four metrics are achieved through the non‐dominated sorting genetic algorithm II (NSGA‐II). A general method to determine the parameters of the proposed energy absorption branch from the Pareto front based on different preferences is provided. Simulations on PSCAD show that sequential insertion of the proposed energy absorption branch with the optimal parameters is able to suppress the switching overvoltage and limit the fault current to a relatively low extent simultaneously.

This paper presents a study on the performance of a fourth rail direct current (DC) urban transit affected by an indirect lightning strike. The indirect lightning strike was replicated and represented by a lightning-induced overvoltage by means of the Rusck model, with the sum of two Heidler functions as its lightning channel base current input, on a perfect conducting ground. This study aims to determine whether an indirect lightning strike has any influence with regard to the performance of the LRT Kelana Jaya line, a fourth rail DC urban transit station arrester. The simulations were carried out using the Electromagnetic Transients Program–Restructured Version (EMTP–RV), which includes the comparison performance results between the 3EB4-010 arrester and PDTA09 arrester when induced by a 90 kA (9/200 µs). The results demonstrated that the PDTA09 arrester showed better coordination with the insulated rail bracket of the fourth rail. It allowed a lower residual voltage and a more dynamic response, eventually resulting in better voltage gradient in the pre-breakdown region and decreased residual voltage ratio in the high current region.

Lightning performance evaluation is aimed at classifying transmission lines into different risk levels of thunderstorm-induced trip-out. Its applications range from better lightning protection guidance, arrester installation design, transmission line retrofits, and line corridor design. Previous studies fail to consider the real-time lightning intensity, which is an essential factor of lightning trip-out that must not be ignored. This article proposes a novel lightning performance evaluation model based on the idea that the tower, which has a record of lightning trip-out with weaker real-time lightning intensity, is more susceptible to trip out, which means low lightning performance. In order to quantify the lightning intensity, this article puts forward a new definition of lightning intensity which includes three kinds of real-time characteristics, that is the location, the current of lightning strike, and the number of times the lightning movement track crosses the transmission line. More specifically, with the rapid development of lightning location system, a novel Lightning Identification, Tracking, and Analysis algorithm is proposed to search lightning movement track based on a database of 17 million lightning records. When lightning trip-out happens, the lightning performance level is graded according to the real-time lightning intensity. By comparing the similarity of static characteristics, the lightning performance level is extended to the tower, which has no record of lightning trip-out. By comparison with the traditional model, the proposed model is closer to the actual situation and can significantly improve the accuracy of lightning performance evaluation, which is improved by 66.7%.

Based on the actual damage data of high-voltage electrical equipment in electric substations in the Wenchuan earthquake, this paper uses the cumulative Gaussian distribution function to describe the relationship between the damage rate of high-voltage electrical equipment and the instrumental seismic intensity. The instrumental seismic intensity at strong motion observation stations in the Wenchuan earthquake is calculated, and the Kriging interpolation method is used to estimate the instrumental seismic intensity at 110 kV and above voltage level substations in Mianyang, Deyang, Guangyuan, and Chengdu of Sichuan Province. A cumulative Gaussian distribution function is then used to fit the damage rate-instrumental seismic intensity relationship curve for six types of high-voltage electrical equipment such as the transformer, circuit breaker, voltage mutual inductor, current mutual inductor, isolating switch, and lightning arrester. The results show that transformers have the highest vulnerability during earthquakes, and they suffered a certain level of damage even under low instrumental intensity. The second most vulnerable equipment is the circuit breaker, followed by the lightning arrester, transformer, and isolating switch, which share a similar vulnerability curve.

Aging of metal oxide surge arresters is mainly affected by the high electric stress near the high voltage electrode. It has been observed that the distribution of voltage and electric field along an arrester is non‐uniform. In this paper, the effect of grading ring geometrical parameters is investigated in order to achieve a more uniform electric field and voltage distribution. A 3D finite element method was employed based on COMSOL MULTIPHYSICS software to calculate these latter. The optimal design of grading ring is achieved by minimizing the electric field along the active column of varistors using a reduced number of simulations based on the Taguchi design and a bat algorithm. Initially, simulation results for a single grading ring were analysed. By using an optimal design of the single ring, the electric field is reduced by 42% in the top of the 220 kV metal oxide surge arrester and the voltage distribution can be improved. It was proposed to install an additional ring at the top of the metal oxide surge arrester. Simulation results shows that using of an optimal design of grading rings, the distribution of voltage and electric field along the surge arrester can be made as uniform as possible.

The DC solid state circuit breaker (SSCB) is the key equipment to construct the DC distribution network. In this paper, an improved topological scheme of RC buffer and metal oxide arrester (MOA) in parallel is proposed, which can not only improve the capacity of circuit breaker to cut off large current, but also reduce the pressure of MOA absorbing energy and shorten the time of fault clearing. A 10kV DC SSCB is designed based on the proposed topology, and a model of the influence of different RC buffer parameters on MOA and DC SSCB is built in PSCAD. The simulation results show that the energy absorbed by MOA is linearly decreasing with buffer capacitance C s and total inductance L of the system. As the buffer resistance R s increases, the energy absorbed by the MOA decreases first and then increases. Too small snubber resistance will cause the DC SSCB breaking overvoltage and fault current to oscillate; excessive snubber capacitor will cause the DC SSCB breaking overvoltage to be too high. Therefore, it is necessary to select the optimal RC parameters under different fault currents, which can not only reduce the pressure of MOA, but also improve the shutdown capability of DC SSCB.

Zinc oxide (ZnO) lightning arresters have good protection performance and have been widely used in power systems. ZnO varistor is the core component of the arrester, and its electrical performance determines the overvoltage protection level of the arrester. ZnO varistor will produce space charge accumulation phenomenon under the action of electric field. In order to study the space charge characteristics of ZnO varistors more deeply, a bipolar carrier transport model considering the change of grain boundary structure was established, and the law of carrier migration in ZnO grain boundaries was simulated. From the three aspects of pressure time, ambient temperature, and depletion layer density, the space charge distribution inside the grain boundary, Schottky barrier height, and grain boundary leakage current are systematically studied.

Fracking is widely applied to enhance shale gas mining, and insight into the fracture behaviors of shale rocks is important. To characterize the fracture properties of Lower Silurian Longmaxi shale, a chevron-notched deep beam specimen, which inherits the advantages of notched deep beam and chevron-notched specimens, is introduced, and several three-point bend tests were conducted on the Longmaxi shale specimens in three principal fracture orientations: the divider, short-transverse, and arrester orientations; the anisotropy in the critical shape coefficient, fracture toughness and fracture energy were then examined and highlighted. The results demonstrate that the critical shape coefficient depends on the anisotropic elasticity of the investigated shale, and a maximum error in the calculated fracture toughness of 9.2% could occur if a critical shape coefficient for isotropic rock is adopted. For the tested shale, the mode I fracture toughness in the divider orientation is close to that in the arrester orientation, with both values being approximately 1.5 times that in the short-transverse orientation; in addition, a progressive decrease in fracture energy from the arrester orientation to the short-transverse orientation is apparent. The fracture surface morphology was observed by scanning electron microscopy, and obvious material deterioration was found near the fracture surfaces for the arrester and divider samples.

The single-phase-to-ground fault (SPGF) affects the reliability and security of the distribution system greatly. Accurate online recognition of fault causes can help improve the efficiency of weak components finding and maintenance. In this article, various symptom features of the SPGF by typical causes are analyzed and a fuzzy inference system (FIS) for fault cause recognition is established for overhead lines in nonsolidly earthed distribution networks. Based on the survey of fault causes in a certain city in China, artificial grounding experiments are designed for six typical fault causes, including arrester breakdown, insulator flashover, line-to-crossbar discharge, line fallen on wet mud, line fallen on wet sand, and line fallen into the pond for waveform data collection. Through multiple time–frequency analysis on waveform data of various causes, five features are extracted and the statistical results are obtained, including self-recoverability, zero current time, transition time, degree of distortion, and randomness. Based on the above, a FIS for cause recognition for SPGFs is established. The experimental results and the comparison with the BPNN model show that the proposed method has good performance and feasibility.

This paper demonstrated the design of a Metal Oxide Surge Arrester for a 132 kV system with a rated voltage of 120 kV according to specifications. The study model was chosen to be Pinceti model which is a derivation of the IEEE standard model of Lightning arrester design. The design specifications for the lab tests on 120kV rated arrester for ZnO material were obtained from the catalogue of Ohio Brass Pvt. Ltd. The parameters for the lumped components were derived from the manufacturer’s data sheet while the non-linear characteristic was derived from curve fitting based on the Pinceti provided curves in literature, using Matlab Curve Fitting Tool. The design was simulated on EMTP-RV commercial software and the results before optimization as well as after optimization are presented. A cross comparison with the manufacturers data results in 1.113% relative error, which is in competition with similar designs for different rated and system voltages in literature. The study presents an improved model of a metal oxide arrester for 132kV system, with its lumped and exponential parameters presented in detail.

The thermal behaviour of the surge arrester is vital to assess its operational condition. The surge arrester usually shows a process of temperature rising during a long-term operation, particularly after subjecting to a surge. Therefore, the research on the temperature characteristics of ZnO arresters contributes to achieve the goal of the performance changes of the ZnO arresters over different temperatures. In this study, based on four types of ZnO arresters from different factories, the variation of the volt–ampere curve, DC characteristic parameters and non-linear coefficient of the whole ZnO arrester at different temperatures were analysed. The relationship between the temperature and non-linear coefficients was obtained through the method of the extraction of the non-linear coefficients. Through the multiple impulse current tests, the temperature of the arrester was well calculated by measuring the corresponding volt–ampere curve, and the relationship between the surface temperature and V–I characteristics of the arrester is verified by the impulse test results. The obtained results provide a new idea for the application of the surface temperature of the arrester in the performance monitoring of the arrester.

The voltage across a zinc oxide (ZnO) element, in which a lightning impulse current is injected, and the temperature distribution in the ZnO element have been computed using the finite-difference time-domain (FDTD) method. The ZnO element having a length of 36 mm and a radius of 16 mm is represented with many 2 mm × 2 mm × 4 mm rectangular cells, each of which has a nonlinear resistivity in each of the x , y , and z directions dependent on the electric field in each direction and the temperature in each cell. Waveforms of the voltage across the ZnO element and maximum temperatures, computed using the FDTD method, for lightning impulse currents having magnitudes of about 30–65 kA, have been compared with those measured by the authors. Furthermore, the voltage across a 66- or 77-kV transmission-line surge arrester, composed of nine stacked ZnO elements, and the distribution of temperature in the arrester have been computed for a 50-kA lightning impulse current.

This paper describes an air gap that switches one of the sections of capacitive storage, which consists of 234 K41I-7 capacitors (5 kV, 23.4 mF). The arrester is launched from a special plasma initiator. The design of the arrester used elements that allow a large electric charge to pass with the ability for subsequent rapid replacement. The response time delay of the arrester is ~20 μs with instability of the response time of the order of 10 μs. This air gap was used to switch a capacitive storage device consisting of 160 K75-100 capacitors (176 mF, 6 kV).

This study introduces an arrangement of surge arrester, Rogowski coil, and triac to attain service continuity of distribution networks. This new arrangement is proposed to limit the arrester failure due to lightning flashes striking distribution feeders. The arrester failure is probably happened due to the increase of absorbed energy over the withstand capability. As the lightning flash has multiple discharges, an equivalent single wave model is computed to evaluate the arrester discharge energy. The arrester discharge current is monitored using a single Rogowski coil. Then, the arrester's dynamic characteristic (current–voltage) is utilised to estimate the discharge energy using only the arrester current. The arrester and associated Rogowski coil are distributed in an 11 kV distribution network. Due to travelling-waves reflections of the direct lightning striking the distribution feeder, the discharge energy of the installed arresters in the network is different than the computed energy using the lightning flash current as an impulse current source directly applied on the arrester device. Finally, the parallel triac with the arrester is suggested and triggered for limiting the arrester's failure. The detailed model of this proposed arrangement is evaluated via an electromagnetic simulation software. The failure assessment is statistically evaluated using the MATLAB software.

形態: カラー図版あり, Physical characteristics: Original contains color illustrations, Accepted: 2020-08-05, 資料番号: PA2120014000

This paper proposes a time-domain method to calculate the fault response in multiterminal dc (MTdc) grids and the performance of hybrid dc breakers. The proposed method, based on traveling waves: 1) provides a sound representation of fault performance by considering all created traveling waves; 2) introduces a new approach to estimate the reflection coefficients; and 3) provides an approximation of the worst case fault location. Then, based on the analytical results, three parameters of the hybrid dc circuit breaker, i.e., current limiting reactor, arrester rated voltage, and time delay are optimally selected with respect to maximum overcurrent, maximum overvoltage, fault clearance time, and energy absorption in arresters through multiobjective optimization. Accuracy and performance of the proposed method are evaluated and verified by time-domain simulation studies in the power systems computer aided design (PSCAD)/electromagnetic transients including DC (EMTDC) environment using frequency-dependent models. The results confirm reasonable accuracy of the proposed fault performance calculation and represent a further step towards optimized design of hybrid dc circuit breakers.

We report the results of laboratory investigations of the behaviour during explosion mitigation by channels typical of those used in commercial explosion arrester devices. Experimental results are presented first of shock and detonation wave interaction with a miniaturized matrix of narrow channels aligned parallel to the incoming flows. The results with a larger scale device using the same channel dimensions tested at more extreme conditions representative of overdriven detonation certification test conditions are consistent with the reduced scale laboratory measurements. To evaluate the applicability of laboratory scale evaluation of arrester elements for other types of explosion arrester, a further preliminary study is also reported with deflagration arrester elements. Finally, the present observations are interpreted in the light of published theories potentially relevant to explaining successful explosion mitigation, or otherwise, by commercial arrester devices. Using this approach, laboratory scale measurements are shown to be as a useful tool for investigating the dominant explosion mitigation mechanisms relevant to practical end user application safety devices and provide an opportunity for assisting with the design and evaluation of practical explosion, especially designs that could be supported by more comprehensive detailed CFD simulations where the supporting laboratory test configurations could also facilitate the use of more sophisticated diagnostic methods

The peak value of continuous operating voltage (PCOV) has a direct influence on the reference voltage of valve arrester, which appreciably influences the manufacturing cost of the line-commutated converter (LCC). Since simulations with high accuracy based on broadband models are memory intensive and time consuming, it is important to determine the operating conditions for PCOV calculation to reduce computational burden. This study establishes piecewise expressions of ideal valve voltages in different converter operation modes, which is the basis for the investigation of commutation overshoots. A simplified circuit is established to evaluate the valve voltage stress, with a modification introduced on the calculation of voltage peaks across blocking valves, which is neglected by previous literature. Then, this study proves theoretically that the 6-pulse rectifier operation mode and the long-term overload power transmission with the maximum delay angle should be the corresponding operating condition for PCOV calculation. Conclusions derived from the analytical analysis have been validated by simulations based on broadband models for practical projects.

Monitoring and diagnostics of metal-oxide surge arresters (MOSAs) have been a research topic for decades. During these years, many monitoring and diagnostic methods have been developed. However, only a few studies perform a comparative analysis of these methods with respect to their performance in different operating conditions. This study briefly explains the most commonly analysed MOSA monitoring techniques and performs a comparative analysis of these techniques on an experimental basis, considering different operating conditions of the arrester. The experimental setting is made to simulate different operating conditions regarding operating voltage root mean square value, voltage harmonics, and temperature conditions. The results show the reliability of MOSA indicators in the analysed conditions, suggesting which indicators and methods should be used for the purpose of MOSA diagnostics.

An increase in transient enclosure voltage can threaten the personal safety of workers and the normal operation of secondary equipment and may cause discharge between the flanges of gas insulated switchgear (GIS) enclosures. This study considered the spark-discharge fault between GIS enclosure flanges of a 500-kV nuclear power plant in China when the disconnect switch is operated in the background. The dynamic arc model during the operation of the disconnect switch was improved in this study, and the equivalent calculation model of transient enclosure voltage (TEV) caused by very fast transient overvoltage generated during the operation of the disconnect switch was established using the electromagnetic transient program ATP-EMTP. Suppression measures of the discharge phenomena were also discussed. The results demonstrated that the transient enclosure voltage caused by the operation of the disconnect switch can reach 75 kV in the most severe case, which causes discharge between the flanges. Reducing the residual charge on the island side of the disconnect switch, installing a metal oxide arrester, and reducing the inductance of the ground wire have different inhibitory effects on this discharge phenomenon, but they all have their limitations. The most simple and effective control measure is to use a short joint between two flanges. The study conclusions can be used as reference for preventing such discharge phenomena.

In ultra HVDC transmission system, arcing horn gap breakdown makes the arc hard to extinguish, threatening transmission safety. Multi-chamber arrester (MCA) is applied in extinguishing the arc to ensure safety. Here, we investigated the arc motion characteristics of the MCA to analyze its arc extinguishing ability. First, a three-dimensional model of the arc plasma in a single chamber was established based on magneto-hydrodynamic (MHD) theory, and the arc motion inside and outside the chamber were analyzed. Next, changes of temperature, velocity and pressure field were simulated. The results showed that the time required for arc totally exiting the chamber is approximately $96~\mu \text{s}$ , the airflow maximun velocity is about 865 m/s, and the highest pressure is more than 4 atm. Particularly, there is a flow reflux at the outlet, as the air flows inward from the outside and form an “oscillation”. Moreover, the arc motion characteristics of different discharge currents within different chamber structure were analyzed. It was found that the spacing between anode and cathode, the radius of electrodes and the outlet radius are the key factors regulating the airflow velocity, and the outlet radius of the chamber has the greatest influence. At last, the accuracy of our model was validated with experimental data.

The presence of stray capacitance in ZnO (Zinc Oxide) surge arresters causes hurdles in arrester operation and non-uniform voltage distribution along the arrester column, especially for High Voltage (HV) and Extra high voltage (EHV) applications. Since the magnitude of stray capacitance is directly proportional to the arrester height; the shortening of surge arresters is a preeminent method to enhance the arrester performance and voltage distribution. Particularly, this stray capacitive effect delays the arrester operation from in-action to action mode, especially against very fast surges. Moreover, the shortening of the arrester column improves the voltage distribution and hence the electric field varies between the stacks. Therefore, this research work focuses on the preparation of two new high gradient arrester materials doping with rare earth oxides. The microstructures of the newly developed materials are analyzed. It is found that there is a reduction of grain sizes and an increase of voltage gradients in the newly developed arrester materials. From this, the height requirement per unit is estimated and compared with the conventional ZnO arrester. Using these high gradient materials, the reduction of height and compactness of the arrester assembly may be achieved greatly. Thus, the developed ZnO surge arrester with high gradient materials enhances the arrester behavior with the attendant improvement of voltage distribution due to its reduced height and stray effect.