Electric Power Equipment Research Articles

Modelling and ride analysis of a hydraulic interconnected suspension based on the hydraulic energy regenerative shock absorbers

Abstract The suspension system is an important part which can mitigate the influences of vibration caused by road roughness where these vibrations are traditionally dissipated by shock absorbers. From the view of energy recovery, a hydraulic interconnected suspension based on the energy regenerative shock absorbers (HIS-HESA) is proposed to improve ride comfort, road holding ability and energy recovery ability simultaneously. This paper mainly focuses on the modelling and ride analysis of a 7-DOF full vehicle suspension model integrated with the HIS-HESA. The mathematical model of the HIS-HESA is described based on the relationship between the pressure drop and the flow rate of every hydraulic element. The characterization of the HIS-HESA is given based on a parametrical analysis under a sinusoidal excitation. Further, the traditional shock absorber and the single HESA have been compared terms of suspension dynamics and energy recovery. Thereafter, the simulation is implemented to compare the vehicle dynamics (body acceleration, tire dynamic load and power regenerated) using HIS-HESA with that of the traditional suspension. The simulation results suggest that the HIS-HESA can attenuate the vibrations to maintain a good ride comfort besides it can also regenerate energy to power electrical equipment on the vehicle. The analysis also indicates that the influence of external resistance within HIS-HESA provides the possibility regarding the semi-active control of the HIS-HESA which will be the research focus in future development.

Optimum Coordination of Overcurrent Relays using Genetic Algorithm and Particle Swarm Optimization

Electrical Systems are seldom subjected to excessive currents caused due to short circuits and ground faults. Therefore, it is mandatory to protect people and primary electric power equipment from damage or disaster using suitable Protective systems. When the current exceeds the threshold level, Overcurrent (OC) Relay is operated. It is important for a protection engineer to maintain coordination time interval (CTI) among relays during overcurrent relay coordination. For quick clearance of faults, various optimization algorithms are applied to relay parameters. In this paper, Genetic algorithm and particle swarm optimization technique are used to deduce the Time Multiplier Setting (TMS) values of relays implemented on a radial network. This aids in achieving suitable OC coordination of relays.

An Experimental Study of the Inductance Parameters of a Smoothing Filter Reactor with a Completely Closed Magnetic Flux

The use of advanced structural concepts for development of electric power equipment of dc traction power supply systems allows one to triple the power density per unit volume. An armored rod radial–cylindrical magnetic system with massive nonlaminated design elements, which is split into sections by nonmagnetic gaps, allows one to provide high mechanical strength without using additional fasteners and pressing elements. This design also provides an admissible level of hysteresis and eddy current losses, as well as meeting the requirements for unconditional linearization of a magnetic flux in the range of working currents. The latter is caused by the performance of smoothing reactors as parts of high-power rectifiers that feed rolling stock.

Intelligent analysis and early warning model of grid meteorological disaster risk

Meteorological disaster is an important factor that affecting the operation of power system stability. Through data mining the relationship between the electric power equipment failure, the limit of water, and the meteorological disaster, we can find the main meteorological factors that cause failure or the limit. In order to effectively reduce the security risk of power grid operation, it is necessary to alarm the fault or the risk of exceeding the limit in advance.

The Effect of Alternating Current Frequency on the Mass and Size Parameters of Transformers and Small-Power Induction Motors

The ac frequencies of 50 and 60 Hz, which are accepted in world practice, have not been substantiated technically and economically as the best for all components of the electric power systems, electrical installations and electrical equipment. Moreover, theory and practice show that, for many electromagnetic and electromechanical devices used in aircraft and water vessels, in construction and road construction machinery with motorwheels, in the agriculture industry, in the timber and timber-processing industry, and in other economic and infrastructural spheres, ac overfrequencies (f > 60 Hz) are preferable. Meanwhile, on the one hand, the wide range of frequencies (100–500 Hz) is considered the optimum, and, on the other hand, the cumbersome analytical expressions for substantiation and calculation of specific machines equipped with the electromagnetic devices, normally including transformers and the widely used inductions motors, are proposed. Simplified procedures for the analysis of the effect of ac frequency on the mass and size parameters of transformers and low-power induction motors are proposed in this article. They allow narrowing the optimum frequency range down to 200–400 Hz and obtaining acceptable results from engineering calculations of this effect.

Arrival Time Difference Estimation of Ultrasonic Signals from Partial Discharge in Electric Power Equipments

Partial discharge of power equipment is one of the common faults in power systems. How to quickly and accurately determine the location of partial discharge is a problem that needs to be solved in practice. The signal arrival time difference estimation technique in signal processing is one of the effective methods to solve this problem. When the power equipment is partially discharged, an ultrasonic signal is generated. Therefore, the local discharge can be positioned according to the ultrasonic signal, however, the traditional signal arrival time difference estimation methods are not ideal for the actual low signal-to-noise ratio and narrow-band ultrasonic signals. In this paper, an improved correlation coefficient waveform comparison time difference estimation algorithm based on complete ensemble empirical mode decomposition with adaptive noise（CEEMDAN）, threshold denoising is proposed, referred to as CEEMDAN-TDE. Firstly, according to the characteristics of the actual ultrasonic signals, the double-exponential decay oscillation model is used to model the partial discharge ultrasonic signals, and Gaussian white noises are added as the interference signals. secondly, the CEEMDAN threshold denoising is used to improve the signal-to-noise ratio of the partial discharge signals; thirdly, the cross-correlation coefficient is calculated, then the arrival time difference can be obtained by comparing the waveforms of the correlation coefficients, and the partial discharge location information is known. The computer simulations of the CEEMDAN-TDE method, and the generalized correlation method, LMS method, and correlation coefficient waveform comparison method estimation are performed. Experimental results show that the estimating performance in arrival time difference of proposed method, CEEMDAN-TDE, is better than the other three methods’ under low SNR and narrowband. The CEEMDAN-TDE method has the hopeful more application in practice.

Decision Model for "Going Global" of China’s Electric Power Technology and Equipment

This paper analyses the status, opportunities and challenges of China’s "going out" of power technology and equipment, points out the problems faced by export of China’s power technology. Based on the market analysis, a decision analysis model for the "going global" market of power technology and equipment for China’s power technology enterprises is designed, by combining the coefficient of variation method with the comprehensive index method.

Разработка метода проверки комплексов цифровой релейной защиты электроэнергетических установок

Разработка метода проверки комплексов цифровой релейной защиты электроэнергетических установок

The Location of Partial Discharge Sources Inside Power Transformers Based on TDOA Database With UHF Sensors

This paper proposes a new method to locate the partial discharge (PD) sources inside the high-voltage power transformers with ultra-high frequency (UHF) sensors, based on the time difference of arrival (TDOA) database. A TDOA database includes the TDOA information of possible PD sources inside a power transformer, which is established under the construction of the system of the tested power transformer and the high accuracy of the minimum distance between a possible PD source and a UHF sensor. We employ the tangent transmission model of PD signals and the shortest path algorithm to solve the distance problem in case of an obstacle obstructing the transmission of PD signals. In order to verify the feasibility and accuracy of this new TDOA database method, we carry out two experiments. One experiment was conducted with a 110kV power transformer and the other was carried out with a platform for PD of electric power equipment. The experimental research results which are composed of location coordinates, transmission path and TDOA information indicate that the TDOA database method can locate single PD source as well as multiple PD sources simultaneously with the location error less than 0.3m.

Анализ методов измерения величины молекулярного веса полимерных материалов изоляционной конструкции энергетического оборудования в процессе его эксплуатации

The need of solving the problem concerned with measuring the polymerization degree (molecular weight) of polymeric dielectric systems is stemming from its practical significance, which implies the availability of a reliable polymerization degree measurement method that would fully meet the power equipment maintenance requirements. The problem is rather intricate in nature, and the requirements are quite stringent. In 2017, the Public Council of Specialists for Diagnostics of Power Electrical Equipment at the Engineering Technical Center (ETC) of UralEnergoEngineering commenced studies of existing and newly developed methods for estimating the polymerization degree of insulating papers that form the insulating structure of power electrical equipment. These studies were carried out with participation of scientific groups, which used different approaches to solving the stated problem. The article presents the results from discussion of polymerization degree measurement methods differing from each other in nature (chemical, optical and electrical), which were outlined in the reports presented at the Interregional Scientific and Practical Workshop held in the Smolensk Branch of the National Research University Moscow Power Engineering Institute (NRU MPEI) on April 26, 2018. It is emphasized (ETC of UralEnergoEngineering, Associate Professor V.N. Osotov) that the chemical method recommended by the relevant regulatory documents does not allow to get a full idea about the paper insulation ageing degree. Indirect methods (analysis of gases dissolved in oil, content of furans in it, etc.) do not yield a quantitative assessment of the ageing degree of the operating insulation system. Alternative methods of nondestructive testing and devices for estimating the polymerization degree of insulating papers: the spectral one (developed by Professor V.K. Kozlov from the Kazan Power Engineering University) and the method of dielectric absorption currents (developed by Professor V.A. Chernyshev from the Smolensk Branch of the NRU MPEI) meet the power equipment maintenance requirements to a fuller extent.

Criteria of creating a multi-level system of electrical equipment diagnostics, control and protection

The reliability of the power electrical equipment (EE) of industrial enterprises, agriculture and medical institutions largely depends on the operating modes and power quality of the supply network. The existing methods of protecting EE, of an X-ray CT scanner, for example, act selectively and their actions are aimed at identifying and protecting electrical equipment from a certain type of a defect. This paper considers the criterion for creating a unified system of control, diagnostics and protection, which is – «EE + supply network» as a unified complex for controlling the switching modes of EE. The total volume of the system consists of five levels of protection types. The number of levels is determined by the type of EE and the magnitude of the possible estimated damage. The first level of protection is the diagnostics of the network state – the initial and subsequent continuous monitoring of the line voltages level and the rate of change of the front of the supply voltage first harmonic component. The second level is the diagnostics of the causes of the current-carrying lines breakage. The third level of protection is EE temperature protection and diagnostics of the thermal overloads causes. The third level is continuous monitoring of temperature indicators of EE. The fourth level is continuous monitoring of bolted connections temperature indicators. The fifth level is control of the insulation resistance value and diagnostics of the reasons for its decrease; moisture isolation protection; EE life prolongation, reliability and trouble-free work ensuring

Influence of trace H 2 O and O 2 on SF 6 decomposition products under arcing conditions in electric power equipment

SF6 has been widely used as an insulating and arc extinguishing medium in electric power equipments. Detection of gas decomposition products is an important means for condition monitoring and fault diagnosis. Trace H2O and O2 have a significant influence on the species and concentrations of SF6 decomposition products. It is important to explore the influence mechanism of trace H2O and O2 on SF6 decomposition products under arcing conditions. A series of SF6 decomposition tests were carried out on a 40.5kV SF6 circuit breaker, and a gas chromatograph and an electrochemical sensor were used to measure decomposed components. First, the H2O content remained constant, and the O2 content and arcing energy changed in the tests. It has been found that the decomposition products of SF6 are SOF2, SO2, CO, CO2, CF4, C2F6 and C3F8. Then, the O2 content remained constant, and the H2O content changed. The decomposition products are mainly SOF2, SO2, CO and CO2. Concentrations of all these decomposition products increase first and then tend to be stable slowly over time, but change differently with the increase of H2O and O2 contents, because H2O and O2 play different roles in the formation process of each decomposition characteristic components.

Magnetic flux control laws in differential electric drive

This paper considers scheme options of the multimotor differential electric drive system. These schemes have competitive energy and weight-size parameters. The number of independent control commands exceed the number of controlled coordinates. Magnetic flux magnitude of the electric machine may be accepted as a control command. Methods of nonlinear programming synthesized the flux control laws in a multimotor differential electric drive system. The minimum weight-size characteristic of the electric power equipment was taken as an optimization criterion. Possibility of founded control laws approximation was shown by the simple piecewise linear equation. Speed control of the electric drive was changed only by one electric machine flux for each of the segments. Fluxes of other machines remained unchanged, equal to the nominal values. Additional losses did not exceed few percent in case of refusal from the exact control law in the area of small loads. Also, it was not observed in the rated area at all.

Temperature detection technology of power equipment based on Fiber Bragg Grating

Abstract The temperature detection and alarm system of power equipment is supposed to be used in power accidents caused by overheating. In our experiment, we build a system to detect the temperature of electrical power equipment. According to the actual temperature fitting curve, the whole system uses the Fiber Bragg Gratings as the signal sensing and transmission media, using the tunable Fabry-Perot (FP) cavity filter to demodulate the fiber and a SLED light source which is considered high reliability. System control and signal processing is carried out by the STM32F407ZGT6 microcontroller and its internal single-cycle DSP. The system has the characteristics of strong anti-interference ability, high reliability and precision, simple installation, convenient maintenance, remote signal transmission.

Effects of filler loading and surface modification on electrical and thermal properties of epoxy/montmorillonite composite☆☆Project supported by the National Natural Science Foundation of China (Grant Nos. 21806129, 51872238, 51407134, and 51521065), the China Postdoctoral Science Foundation (Grant No. 2016M590619), the Natural Science Foundation of Shandong Province, China (Grant No. ZR2016EEQ28), the State Key Laboratory of Electrical Insulation and Power Equipment,

Epoxy-based composites containing montmorillonite (MMT) modified by silylation reaction with γ-aminopropyltriethoxysilane (γ-APTES) and 3-(glycidyloxypropyl) trimethoxysilane (GPTMS) are successfully prepared. The effects of filler loading and surface modification on the electrical and thermal properties of the epoxy/MMT composites are investigated. Compared with the pure epoxy resin, the epoxy/MMT composite, whether MMT is surface-treated or not, shows low dielectric permittivity, low dielectric loss, and enhanced dielectric strength. The MMT in the epoxy/MMT composite also influences the thermal properties of the composite by improving the thermal conductivity and stability. Surface functionalization of MMT not only conduces to the better dispersion of the nanoparticles, but also significantly affects the electric and thermal properties of the hybrid by influencing the interfaces between MMT and epoxy resin. Improved interfaces are good for enhancing the electric and thermal properties of nanocomposites. What is more, the MMT modified with GPTMS rather than γ-APTES is found to have greater influence on improving the interface between the MMT filler and polymer matrices, thus resulting in lower dielectric loss, lower electric conductivity, higher breakdown strength, lower thermal conductivity, and higher thermal stability.

The method for increasing the efficiency of equipment’s maintenance in railway traction power supply systems

Purpose. To develop the method for increasing the efficiency of the equipment’s maintenance and repair system, ensuring necessary level of operational reliability of the equipment, safety and reliability of the electric equipment with minimal expenses on operation. Relevance. Aging of the power equipment in railway power supply systems sharply raised a need for assessment of its states and degree of risk for operation outside rated service life. In critical conditions of technological processes and operational modes of the railways it is necessary to increase the equipment’s operational reliability. The scheduled maintenance and repair system whose main technical and economic criterion is the minimum of equipment’s downtimes on the basis of a rigid regulation of repair cycles, in the conditions of market regulations in the field of repair in many cases does not provide the optimal decisions due to insufficient financing. The solution of this problem is possible by improvement of the maintenance and repair system. Under these conditions the main direction for supporting the operational reliability of power electric equipment on TS is a development of the modern methods based on individual supervision over real changes of technical condition of power equipment. Scientific novelty. In this article the authors proposed an integrated approach, on the basis of which can be developed the effective maintenance and repair system for traction power supply systems. Proposed approach allowed to react quickly to changes of service conditions on traction substations, to control the technical condition of power electric equipment under the conditions of uncertainty, to establish interrelation between quality of service and operational reliability of the equipment, to choose a service strategy on traction substations. Practical importance. The validity of the developed method was confirmed by the results of calculations and practically by choosing the optimal maintenance's option for transformer TDTN-25000/150-70 U1 (ТДТН-25000/150-70 У1) on traction power supply substation.

Investigation on volt-ampere characteristic of secondary arc burning in atmospheric air

The secondary arc, as a common phenomenon in a high voltage power transmission system, is an essence of an electric arc. It not only damages the electrical power equipment but also threatens the safety of the power system. A series of experiments on the secondary arc have been conducted in this work. The volt-ampere curves are measured, the motion trajectories are captured, and the centroid of the secondary arc body is calculated by means of image processing. The experimental results indicate that the secondary arc length can reach several meters, and its volt-ampere curve is completely different from that of short-gap arcs and others operated in some special dielectrics such as vacuum. The evolution of the secondary arc can be generally divided into two stages. In the early stage, the arc column performs a vertical motion and has an upward trend due to thermal buoyancy. Basically, the volt-ampere curve has a shape of a regular hysteresis loop. The impacts of the frequent short-circuit behavior of the arc column on the volt-ampere curve and arcing time are investigated. At the later stage, the secondary arc temperature drops and the zero-off behavior becomes obvious. The volt-ampere curve is inevitably affected. The zero-off duration is obtained, and the key factors are discussed. The dynamics of charged particles in the zero-off interval are analyzed. Furthermore, under the effect of strong wind, it has been found that the secondary arc current is occasionally forced to zero and preceded by the voltage. The mechanism for such a phenomenon is first elucidated from the perspective of energy balance. The results lay a theoretical basis for secondary arc physics.

Application of functional safety to electrical power equipment and systems in process industries

In process industries, the application of functional safety in preventing major incidents is a well-established practice. The functional safety standard IEC 61511 (IEC, 2016) is applied to the safety instrumented system (SIS) protection layers to avoid the undesired events or reduce the likelihood of the events or impacts due to failures in the process, process equipment, or its control system including human interactions. However, there are risks of catastrophic incidents due to electrical equipment failures as well. Therefore, one should not underestimate the importance of the management, design, installation, operation, and maintenance of electrical power systems and protection devices. Regulatory authorities, in some countries, require the owners or operators to address the risks that arise from electrical equipment failure.The risk-based assessment, allocation of safety functions to protection devices, the establishment of integrity requirements, design, installation, operation, and maintenance of electrical protection devices must be managed like the protection layers for the process units. This paper focusses on the application of IEC 61511 to the protection of electrical equipment and systems, available industry guidelines, and the unique challenges in implementing the functional safety standards. The paper guides the electrical engineers with an example risk assessment, identification of protection device and its safety integrity level (SIL), verification of the reliability of the protection device and establishing a maintenance and operation program.

INFLUENCE OF BACKLASH ON AMPLITUDE OF EXCHANGE POWER FLUCTUATIONS IN AUTONOMOUS ELECTRIC POWER EQUIPMENT

The application of autonomous electric power equipment having in their composition parallel operating diesel-generator sets on the basis of synchronous generators is considered. The problem of existence of exchange power fluctuations in such technical systems is described. A mathematical model has been developed that makes it possible to carry out investigations of an autonomous electric power equipment. The technique for constructing maps of the amplitude of the exchange power fluctuations, from the backlash gaps in the speed control circuits of diesel generators is obtained. The use of such cards makes it possible to introduce recommendations on limiting the amplitude of exchange power fluctuations to normative documents, both of a general nature, and specifically for certain types of equipment. In the same way, the cards make it possible to determine the gap gaps existing in the frequency control loop from the measured amplitudes of the exchange power fluctuations.

Insulation characteristics of fluoronitriles / CO2 gas mixture under DC electric field

Environmentally friendly DC gas insulated transmission line (GIL) is currently one of the hot topics in advanced electric power equipment. Recently, fluoronitriles have been widely studied and considered to replace SF6 in GILs. In this paper, the breakdown voltage, insulator flashover voltage, and the partial discharge inception voltage of fluoronitriles/CO 2 gas mixtures are reported in a DC electric field. The mole ratio of the mixed gases are 4 : 96 % and 8 : 92 %, and the gas pressure is in the range 304.7 to 717.83 kPa. Based on the results, the breakdown field strength of fluoronitriles/CO 2 gas mixture shows a growth tendency with increasing gas pressure in a uniform electric field. At 717.83 kPa, the positive breakdown field strength is higher than the negative and reached a maximum. In a non-uniform electric field, the negative breakdown voltage of fluoronitriles/CO 2 gas mixture increases with increasing gas pressure. In the contrast, the positive breakdown voltage decreases with the rise of gas pressure, which exhibits a significant polarity effect. The flashover voltage of fluoronitriles/CO 2 gas mixture increases with increasing gas pressure. At the same gas pressure, the negative flashover voltage is slightly higher than the positive. The negative flashover voltage of fluoronitriles/CO 2 gas mixture at 717.83 kPa is equal to 96.06 % of SF6 gas at 0.5 MPa abs. The negative partial discharge inception voltage (PDIV) of the fluoronitriles/CO 2 gas mixture is greater than the positive, and both 4 : 96 % and 8 : 92 % gas mixtures showed higher PDIV than the SF6. Considering the insulation characteristics, the fluoronitriles/CO 2 mixture has the potential to replace SF6 in DC gas insulated transmission lines.