Short-circuit Tests Research Articles

Improved fault location method for AT traction power network based on EMU load test

The autotransformer (AT) neutral current ratio method is widely used for fault location in the AT traction power network. With the development of high-speed electrified railways, a large number of data show that the relation between the AT neutral current ratio and the distance from the beginning of the fault AT section to the fault point (Q–L relation) is mostly nonlinear. Therefore, the linear Q–L relation in the traditional fault location method always leads to large errors. To solve this problem, a large number of load-related current data that can be used to describe the Q–L relation are obtained through the load test of the electric multiple unit (EMU). Thus, an improved fault location method based on the back propagation (BP) neural network is proposed in this paper. On this basis, a comparison between the improved method and the traditional method shows that the maximum absolute error and the average absolute error of the improved method are 0.651 km and 0.334 km lower than those of the traditional method, respectively, which demonstrates that the improved method can effectively eliminate the influence of nonlinear factors and greatly improve the accuracy of fault location for the AT traction power network. Finally, combined with a short-circuit test, the accuracy of the improved method is verified.

Design and application of short circuit test scheme for Hu Zhou DPFC project

The short circuit test of distributed power flow controller (DPFC) is still a blank in the world. In order to test the effectiveness and adaptability of DPFC in case of line failure, it is necessary to carry out short circuit tests in DPFC projects. Based on the Hu Zhou DPFC Project, this paper proposes the control and protect strategy of DPFC which is coordinated with the protect strategy of AC line, designs single phase short circuit grounding test scheme of the AC line where DPFC is located. In the application, the action logic of DPFC under single-phase grounding fault is verified, the single phase short circuit test of DPFC were completed for the first time, and the transient voltage and current were obtained. It provides technical support for the popularization and application of DPFC project.

Research on large-capacity impulse test technology for distribution transformer based on energy storage intelligent power

Large-capacity impulse test of distribution transformer requires a large amount of instantaneous energy, while the impulse mode of conventional dedicated high-voltage line and generator requires synchronous switch, adjusted impedance, generator, etc., which has low operability and the risk of affecting system stability. To solve the problems in the large-capacity impulse test of distribution transformers, this paper proposes a high-current impulse test method based on energy storage technology, power electronics technology and intelligent control technology. The stepless continuous adjustable voltage of large capacity short circuit test, precise control of test current peak factor and stable output are realized, and the corresponding smart energy storage power supply for the large capacity test of a distribution transformer is developed. Through simulation and live test, the design of the energy storage intelligent power supply proposed in this paper greatly reduces the power supply side capacity requirements of large capacity impulse test of power distribution, and has excellent operability in field test.

High-Performance Breaking and Intelligent of Miniature Circuit Breakers.

The exploitation and utilization of clean energy such as wind and photovoltaic power plays an important role in the reduction in carbon emissions to achieve the goal of “emission peak and carbon neutral”, but such a quantity of clean energy accessing the electric system will foster the transition of the electric power system structure. The intelligentization of power equipment will be an inevitable trend of development. High breaking performance, remote control and a digital detection platform of miniature circuit breaker, a protective equipment of a power distribution system, have also been inevitable requirements of the power Iot system. Based on the above, this paper studies three aspects: high-performance AC and DC general switching technology, remote control technology and operation status’ digital monitoring. A new DC non-polar breaking technology is proposed, which improves the short circuit breaking ability. An experimental prototype using the above techniques was fabricated and passed the DC 1000 V/10 kA short-circuit breaking test. On the basis of the above, an intelligent circuit breaker is developed, which contains multiple functions: remote switching, real-time temperature detection, energy metering and fault warning. Moreover, a software for digital condition monitoring and remote control is developed. This work has certain theoretical and practical significance for the development of the power Internet of things.

Effect of nozzle ablation amount on the generation amount of decomposition products for SF 6 circuit breaker

Non-uniform arc burning in the nozzle is a common latent fault of SF6 circuit breaker, which will affect its breaking performance. When arcing, PTFE in the nozzle is vaporized and involved in the formation reaction of SF6 decomposition products. Non-uniform arc burning leads to PTFE excessive vaporization and significantly affects the type and concentration of some SF6 decomposition products, which can provide a basis for the latent fault diagnosis. In this paper, 16 times of 31.5kA short-circuit current breaking tests were carried out by two 40.5kV SF6 circuit breakers respectively. The uniform and non-uniform ablation nozzles were obtained. It was found that the concentrations of SOF2, SO2 and SO2F2 were almost not affected by the amount of nozzle ablation. However, when the mass loss of excessive ablation nozzle is 1.8g more than the normal one, CF4, C2F6, CS2 and CO2 of excessive ablation nozzle are 807.5uL/L, 22.5uL/L, 9.0uL/L and 116.9uL/L more than the normal one, respectively. CF4, C2F6, CS2 and CO2 can be used as characteristic decomposition products to diagnose non-uniform arc burning in the nozzle. This study is of great significance for the latent fault diagnosis of SF6 circuit breakers based on decomposition product analysis.

Safety Assessment for External Short Circuit of Li-Ion Battery in ESS Application Based on Operation and Environment Factors

In recent years, the demand for medium and large secondary batteries in EV (electric vehicle) and ESS (energy storage systems) applications has been rapidly increasing worldwide, and accordingly, the market size is increasing exponentially. However, the recent fire accidents related to secondary batteries for EVs and ESS are having a negative impact on the battery market. Therefore, this paper implements an accident simulation device to perform an external short-circuit test, one of the typical safety tests for NMC-series prismatic and pouch-type batteries that are widely used among battery cells used in medium and large secondary batteries. The implemented accident simulation device for the external short-circuit test is composed of short-circuit resistance, measuring device, control device, etc., and is configured to analyze external short-circuit characteristics according to various test conditions. Based on this, an external short-circuit test according to the type, short-circuit resistance and SOC (states of charge) of the lithium-ion battery was performed to confirm the current and temperature characteristics according to each condition. As a result of performing an external short-circuit test for each protection device in the battery module and preprocessing temperature, it is certain that the module fuse operates over 120 times faster than the cell fuse based on the same SOC conditions, and the quantity of electric charge in the module fuse is over 110 times smaller than of the cell fuse in the case of a short-circuit fault. It is also found that the highest and lowest preprocessing temperatures are considered to be severe conditions. Based on the proposed mechanism of an external short circuit in a Li-ion battery and the test device for the external short circuit, it is confirmed that this paper can contribute to the safety assessment of Li-ion battery-based ESS.

Electrical distribution grid of Kirkuk City: A case study of load flow and short circuit valuation using ETAP

The load flow study and short circuit analysis can be considered as the backbone of the electrical power network. This study based on real data collected from 12 substations, each substation contains many feeders provide the electricity network of Kirkuk city (a city in Iraq located at the north of Baghdad). The methodology of this article depended on using the Electrical Transient Analyzer Program (ETAP) software in assessing the performance of Iraqi electrical distribution network (Kirkuk city as a model) by starting modeling and simulation in order to assess the reliability through testing the load flow, and short circuit test. A complete study of load flow assessment of an actual Kirkuk city power distribution network with actual load values is presented (data have been taken from the Directorate of Electricity Distribution of Kirkuk city). The results of modeling the whole city and the detailed reports of this study can give us a comprehensive assessment with the presence of actual loads values, including total demand, PF, transmission line parameters, and the weakness points of the electrical grid.

Susceptibility Issues of Control Instrumentation in Electromagnetic Environment of High Current Laboratory

The paper is a continuation of the research works of the authors. The aim of it is identifying the electromagnetic environment in which the control equipment of the short-circuit test stand operates. Exceptional attention was devoted to the issues related to the operation of the time-phase controller system. Measurements and identification of the electromagnetic environment were carried out on a specific short-circuit test stand, where short-circuit currents are generated by the medium-voltage (MV) short-circuit transformers. Short circuit tests are always preceded by powering the MV side of the test transformer by unloading the low-voltage (LV) side. Thereafter, the controller must wait for the release of the operator to start the test. Sometimes an electromagnetically disturbed controller starts the test without release. Such situation is undesired and can be destructive for the tested objects. Identification of the transient fields during the powering of the test transformer is indispensable for assessing the hazard of EM interference of the controller. Earlier research by the authors showed that the repetitive damped oscillating waves (DOW) are a component of the electromagnetic environment. Adequate instrumentation to cope with the problem are D-dot and B-dot field probes is needed. The paper reports such measurements along with recording the voltage signals. It was suspected that repetitive ignition and extinction of the short arc by closing the circuit breaker in the MV circuit is the origin of the DOW. Additional investigation of the circuit breaker in stand-alone operation is excluded in this hypothesis. The only possibility of the DOW is pulse traveling back and forth in the MV circuit, which is a line with distributed parameters.

Numerical calculation and experimental verification of subtransient- and transient reactances of a pumped storage machine

The subtransient reactance Xd′′ and transient reactance Xd′ of large-capacity alternators are crucial parameters to determine the fault current magnitude and design the protection system for the machine. The traditional calculation method of Xd′′ and Xd′ will bring errors in the graphical decomposition process which depends on the subjective judgement of different individuals, and the analytical method is also inherently imprecise. In this paper, the superconductor simulation method (SSM) incorporated with field-circuit coupled finite element model is presented. The SSM has high accuracy and is capable of considering the saturation effect, skin effect and arbitrary structure of the machine. The unsaturated and saturated values of Xd′′ and Xd′ of a pumped storage machine are calculated with the proposed SSM. The method of establishing the field-circuit coupled model, governing equations and the superconductor simulation method are introduced in detail. The short-circuit test is conducted on the real machine and the calculated results of both Xd′′ and Xd′ are verified by the measured values.

Calculation of current distribution in parallel-connected transformer winding sections in the case of asymmetric magnetic field during short-circuit test

In this paper, an algorithm for calculating the asymmetric current distribution in parallel-connected high-voltage winding sections of a transformer during a short-circuit test caused by an asymmetric magnetic field is described. This calculation is essential in multi-winding transformers, such as traction transformers and rectifier transformers, which have a high-voltage winding consisting of sections connected in parallel, where the number of sections is equal to the number of low-voltage windings and only one low-voltage winding is shorted during the short-circuit test.An optimization method, combined with a semi-analytical transformer model based on conformal mapping, is used to calculate the magnetic field and find a combination of currents in parallel-connected sections assuming equal induced voltages, i.e. flux linkages, in each section.The results of the calculation show good agreement with measurements carried out on the traction transformer for an electric multiple unit.

A novel bidirectional nonuniform hybrid circuit breaker considering different direction protection requirements

Hybrid switching technologies such as zero voltage switching (ZVS) and zero current switching (ZCS) are widely accepted to protect DC power systems from different kinds of faults. However, in some cases such as the protection of DC generators in the electrical distribution system of modern ships, different protection strategies are needed for faults in different directions and both ZVS and ZCS technologies may be needed in one circuit breaker. This special protection requirement will lead to being more complicated in the bidirectional protection of the system and limits the application of the hybrid circuit breakers. Therefore, a novel bidirectional nonuniform hybrid circuit breaker based on a special combination of ZVS and ZCS technologies is proposed to simplify the overall topology of the circuit breaker. The proposed scheme can interrupt high rate-of-rise fault current in one direction by ZCS technology while interrupting short-circuit current in another direction with short-circuit short-delay strategy by ZVS technology. First, the topology and working principle of the proposed bidirectional nonuniform hybrid circuit breaker are introduced. Moreover, three current commutation processes involved in both directions of fault current interrupting are analysed to achieve the optimal connection structure. Furthermore, a high-speed driving mechanism of the vacuum interrupter (VI) based on the flexible conjunction of an electromagnetic repulsion (EMR) driver and a permanent magnetic (PM) system is introduced and the structure of the optimal connection is designed. Finally, the proposed topology of the hybrid circuit breaker is validated using a realistic 800 V/1600 A prototype. The short-circuit breaking off tests of both directions are conducted. The feasibility of the proposed scheme is verified with these tests.

Two Novel Approaches for Identification of Synchronous Machine Parameters From Short-Circuit Current Waveform

In this article, two novel approaches for identifying the synchronous generator (SG) parameters are presented. The proposed approaches use an experimentally obtained armature current during the short-circuit test as input data. Both approaches are simple, cost-effective, and practical since they do not require any additional equipment for signal generation nor applying any of the advanced control techniques. The first approach relies on fitting the analytical total armature current waveform with the experimental one, while the second approach relies on matching the observed waveform with an analytical waveform of asymmetrical and alternating components. Instead of traditional graphical methods typically used in standardized procedures, this article also proposes a novel hybrid metaheuristic algorithm to identify the SG's parameters. The experimental verification of the proposed methods is carried out on 100 MVA SG at the Bajina Basta hydropower plant in Serbia.

Review of Pulse Test Setup for the Switching Characterization of GaN Power Devices

Pulse test techniques are widely adopted in characterizing both the static and dynamic performances of semiconductor devices considering various device structures and operating conditions. For gallium nitride (GaN) devices, due to the current collapse phenomenon, fast and accurate measurement of their key electrical parameters, such as dynamic ON-state resistance <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {ds}, \mathrm{\scriptscriptstyle ON}}$ </tex-math></inline-formula> , switching rising time, fall time, switching losses, and short-circuit (SC) robustness, becomes essential. This article presents a comprehensive review of state-of-the-art pulse test setup methods such as the double-pulse test (DPT), multiple-pulse test (MPT), and SC test (SCT) for the first time, which facilitates the GaN device structure design and practical applications in high efficiency and power density power converters.

New insight on the risk profile pertaining to lithium-ion batteries under thermal runaway as affected by system modularity and subsequent oxidation regime

It is now well established that lithium-ion battery technology is a key electrical energy storage device in the fight against the global warming, helping us to make transportation more sustainable and securing intermittent renewable energy sources. The requirement to keep the thermal runaway (TR) hazard under control is among remaining issues for continuous and sustainable use of lithium-ion batteries. This experimental work brings a new insight on the issue, by performing and analyzing of a series of NMC pouch cell internal short circuit tests reflecting progressively the overall level of integration of such cells when modularly assembled in sub-systems to constitute the full pack. While replicating always the same TR triggering procedure in these experiments, our heat, gas and particle emission analyses reveal that the consequences in terms of chemical (e.g. toxic and corrosive) and thermal threats arising from a default cell running into thermal runaway may greatly vary according of the level of integration mocked up during the abuse test. This work also shows that thermochemical reactions/combustion regimes and their transitions following TR (towards possible flaming combustion or simply ending-up by hot gas degassing) are among key determinants of the whole risk pattern.

Analysis and optimization of leakage impedance in a transformer with additional winding: A numerical and experimental study

Transformers are one of the most important elements of electrical power systems. In several conditions, the same transformer is connected to many different networks with different voltage levels and the replacement of the transformer is one of the most difficult tasks for the power suppliers. Tap winding transformer can be used to overcome the problems of the variable primary or secondary voltages. However, tap winding positions and type significantly affect the overall leakage impedance and it is one of the major concerns for the tap winding transformer designers. In this paper, the tap winding transformer distance was optimized with additional tap winding on the high voltage winding side. To optimize and calculate the leakage impedance in the tap winding transformers with three different voltage levels, finite element analysis was used. The prototype tap winding transformer was manufactured with the help of the finite element method. The difference between the short-circuit experimental test and the finite element method result was less than 1%. The experimental results show that optimal calculation of the leakage impedance in the tap winding transformer can be achieved with help of the finite element analysis.

A Comparative Study on Reliability and Ruggedness of Kelvin and Non-Kelvin Packaged SiC Mosfets

This article evaluates silicon carbide (SiC) <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet’</small> s reliability and ruggedness comprehensively between two widely employed device package types: common source and Kelvin source. Multiple accelerated lifetime tests are conducted to comprehensively investigate SiC <sc xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">mosfet</small> ’s reliability at both package and die levels. Specifically, a conventional high electric field test is applied to induce gate oxide degradation, whereas package degradation is investigated by the widely adopted power cycling test. To mimic gate oxide degradation patterns closer to realistic cases, an active channel gate bias test is proposed in this study, and a fair comparison is made regarding the device's degradation pattern in the conventional high electric field test. Throughout accelerated lifetime tests, devices’ electrical parameters, consumable lifetime, and end-of-life failure modes are comprehensively evaluated. For ruggedness comparison, a single-shot short-circuit test is conducted on both common-source and Kelvin-source packaged devices with the same die technique and configuration. Other than analytical discussions with experimental waveforms, failure analysis is also conducted to investigate the device's failure mode and root cause. In respect of experimental results in accelerated lifetime tests and short-circuit tests, the existence of the common-source inductance and resistance may mitigate the electrothermal stress applied on the chip with lower gate–source voltage under load current and results in mitigated device instability and longer consumable lifetime.

Systematic Analysis and Characterization of Extreme Failure for IGCT in MMC-HVdc System—Part II: Failure Mechanism and Short Circuit Characteristics

Short circuit failure mode (SCFM) of integrated gate commutated thyristor (IGCT) under extreme failure is of vital importance in high voltage direct current power transmission based on modular multilevel converter technology. Due to the sealing housing package of IGCT, the short circuit mechanism is hard to be clarified. Considering this limitation, the current density changes in IGCT with different failure modes are studied under different current levels in a built integrated test system with the placed magnetic sensor array and thermal couple array. Then, the short circuit mechanism of failed IGCT is proposed based on the experimental results. IGCT with turn-<small>off</small> failure performs self-triggering effect due to the focused short current and increased temperature in the initial destruction area, which is usually located in a single position of the outer cathode rings. While IGCT with surge current failure shares the short current among multiple initial destruction areas, which are usually distributed evenly in the wafer area. Scanning electron microscope picture and energy dispersive X-Ray spectroscopy (EDX) analysis show that the formed conducting alloy has spread into the molybdenum plate deeply and the phenomenon of atom diffusion (molybdenum, silicon and aluminum) near the interface is observed. Finally, long term short circuit tests of more than 12&#x00A0;h with both turn-<small>off</small> failure and surge current failure under 3000&#x00A0;A prove the stable SCFM of IGCT.

FINITE-ELEMENT CALCULATION OF ELECTROMAGNETIC FORCES IN THE DEFERENT SHAPES OF DISTRIBUTION TRANSFORMERS WINDING UNDER SHORT CIRCUIT CONDITION

This paper is concerned with calculating the electromagnetic forces in the windings of distribution transformers with different shapes of coils. The electromagnetic forces as well as the magnetic flux density and their distribution were analyzed and calculated using Finite Element Method (FEM). The Finite Element models of the distribution transformers with non-linear magnetic characteristics for the iron core are built using FEM software "ANSYS". In this paper, the static analysis method is based on two-dimensional models, and these models have been solved by using the formula for the magnetic vector voltage (A). Three types of three-phase distribution transformers were adopted, each with a capacity of 250 kVA and a voltage ratio is 11/0.416 kV. These types of transformers with different shapes of coils are stack core transformer with oval coil, wound core transformer with rectangular coil, and stack core transformer with cylindrical coil. The results obtained from the FEM analysis agreed with the design calculations which depend on the conventional design formulas. The most important contributions of this study are to building two-dimensional models for different types of distribution transformers. Calculating electromagnetic forces in transformers winding during short circuit conditions in different coil shapes. Studding the effect of the shape of the coils on the calculation of the electromagnetic forces in them. This work can save time, effort, and cost for transformer manufacturers in calculating the electromagnetic forces, also using this model for the virtual test leads to avoid the risk, and efforts spent to do the real short-circuit test.

Analysis of the Operation of Cascade Current Transformers for Measurements of Short-Circuit Currents with a Non-Periodic Component with a Large Time Constant of Its Decay

Simulations of emergency states and tests of resistance of electrical devices to emergencies are performed in specialized high-power laboratories, the so-called short-circuit laboratories. For most electrical power devices, such measurements are required by international standards. The basic equipment of short-circuit testing laboratories consists of current transformers for measuring short-circuit currents. These transformers should not only enable the accurate conversion of sinusoidal currents—which is typical for conventional current transformers, but also asymmetrical short-circuit currents containing an aperiodic component, which classic current transformers cannot reproduce. Therefore, manufacturers and designers try to meet the market demands and design these special class 0.2 current transformers. To meet the high technical requirements, the field-circuit method with three-dimensional space–time analysis of electromagnetic fields was used during design, considering physical phenomena in ferromagnetic cores (i.e., hysteresis and eddy current losses) and the load of the secondary winding of the current transformer by the measurement system. The article presents simulations of secondary currents for the short-circuit current transformer model, and the results were confirmed by measurements and oscillograms of the currents flowing in the windings of the real model. The prototype of the designed short-circuit transformer meets the IEC/EN standard requirements. When measuring harmonic currents, the transformation errors meet the requirements of class 0.2. During the short-circuit current waveforms, the maximum instantaneous peak error does not exceed 1% of the error for all the subsequent maxima of the current waveform during the specified transient switching cycle. In comparison, the standard allows this error to be 10%.

Analysis and suppression of voltage oscillation at DC circuit breaker terminal in DC fault transient process

High-frequency voltage oscillation occurs at the initial stage of DC short-circuit fault in the modular multilevel converter (MMC)-based high-voltage direct-current systems, which directly threatens the reliable operation of the secondary equipment in DC circuit breakers (DCCBs). Therefore, this paper focusses on the voltage oscillation characteristic at DCCB terminals, considered the stray parameters of connecting lines, the parasitic parameters of main equipment and the impedance of grounding grid, established equivalent circuit models of MMC-HVDC converter station at the initial stage of pole-to-pole and pole-to-ground fault, and obtained the analytical formula for the voltage oscillation frequency. Then, the comparison with the DC short-circuit test data of ±200 kV MMC-HVDC converter station verified the validity of the models and revealed the mechanism of voltage oscillation. Finally, the influence of the parameters of the converter station on the oscillation characteristics was discussed. It was proposed to install the DCCB at the MMC valve's terminal near the DC side, and the oscillation frequency is about 10–60 kHz, which is more than 5 times lower than that at the DC reactor's terminal near the DC pole bus, and the disturbance of oscillation to DCCB was alleviated.