High-voltage Electric Systems Research Articles

Artificial intelligence approaches for accurate assessment of insulator cleanliness in high-voltage electrical systems

Artificial intelligence approaches for accurate assessment of insulator cleanliness in high-voltage electrical systems

Experimental Investigation of Modified Level Shift PWM with Capacitor Voltage Balancing on Single Phase Modular Multilevel Converter

Modular Multilevel Converters (MMCs) are a prominent voltage source converter topology that is rapidly gaining popularity in medium/high power/voltage applications, including high-voltage DC transmission systems and electric vehicle systems. However, MMC has the critical issue of unbalanced submodule capacitor voltages and circulating current. The MMC distributes DC-link energy evenly among its submodule capacitors, rather than storing it in a large capacitor like conventional voltage source converters. In MMC, the submodule floating capacitors interface the DC input voltage and AC output voltage. Therefore, capacitor voltages must be balanced. The existing capacitor voltage control struggles to handle many gate pulses at medium and high voltages. An effective control scheme is needed to solve the issues mentioned earlier. This paper presents a performance analysis of a 1-Φ MMC using a modified level shift PWM technique based on Universal Control Modulation Scheme (UCMS) and a sorting-based capacitor voltage balancing algorithm. MATLAB/Simulink software implements the proposed control method for a 1-Φ , seven-level MMC. The outcomes of the simulation demonstration reveal that phase disposition PWM offers less harmonic distortion of output phase voltage than the other level shift PWM techniques, such as phase disposition PWM and alternate phase disposition PWM. The simulation results also demonstrate the effective use of the sorting-based capacitor balancing algorithm to regulate the voltages of the submodule capacitors. Finally, the real-time GUI tool validates the simulation results using an experimental prototype of 1-Φ MMC with the dSPACE MicroLabBox 1202.

Novel Reference Method for the Characterization of PD Measuring Systems Using HFCT Sensors.

During their lifespan, high-voltage (HV) electrical systems are subjected to operating conditions in which electrical, mechanical, thermal and environmental-related stresses occur. These conditions over time lead to unforeseen failures caused by various types of defects. For this reason, there are several technologies for measuring and monitoring the electrical systems, with the aim of minimizing the number of faults. The early detection of defects, preferably in their incipient state, will enable the necessary corrective actions to be taken in order to avoid unforeseen failures. These failures generally lead to human risks and material damage, lack of power supply and significant economic losses. An efficient maintenance technique for the early detection of defects consists of the supervision of the dielectrics status in the installations by means of on-line partial discharge (PD) measurement. Nowadays, there are numerous systems in the market for the measurement of PD in HV installations. The most efficient with a reasonable cost will be those that offer greater security guarantees and the best positioned in the market. Currently, technology developers and users of PD measuring systems face difficulties related to the lack of reference procedures for their complete characterization and to the technical and economic drawback of performing the characterization tests on site or in laboratory installations. To deal with the previous difficulties, in this paper a novel method for the complete and standardized characterization of PD measuring systems is presented. The applicability of this method is mainly adapted for the characterization of systems operating in on-line applications using high-frequency current transformer (HFCT) sensors. For the appropriate application of the method, an associated and necessary scale modular test platform is used. In the test platform, the real on-site measuring conditions of an HV insulated distribution line are simulated in a controlled way. Practical characterizations, showing the convenience and advantages of applying the method using the modular test platform, are also presented.

Simultaneous Inhibition of Conduction Loss and Enhancement of Polarization Intensity of Polyetherimide Dielectrics for High-Temperature Capacitive Energy Storage.

Polymer dielectrics with excellent high-temperature capacitive energy storage performance are in urgent demand for modern power electronic devices and high-voltage electrical systems. Nevertheless, the energy storage capability usually degrades dramatically at increased temperatures, owing to the exponentially increased conduction loss. Herein, a trace of commercially available aluminum nitride (AlN) nanoparticles is incorporated into the poly(ether imide) (PEI) matrix to inhibit the conduction loss. The nanostructured AlN component with a large specific surface area can provide abundant sites for the collision of carriers. More importantly, the generated new trap energy levels can immobilize the carriers, accordingly contributing to the reduction in leakage current. From this, the discharged energy density at 150 °C of PEI composites increases by 82.13% from 2.63 J/cm3 for pristine PEI to 4.79 J/cm3 for PEI composites. This work establishes a facile approach to enhancing the high-temperature capacitive performance of polymer dielectrics.

Model for Integrating the Electricity Cost Consumption and Power Demand into Aggregate Production Planning

The constant increases in electricity tax costs and the mandatory contracting of power demand in advance by companies connected to the high-voltage electrical system drive organizations to improve energy planning in their production processes. In addition, market uncertainties make only stochastic methods insufficient for forecasting future production demand. To fill this gap, this study proposes a model that integrates the cost with electricity consumption and power demand into the aggregate production planning, considering the market uncertainties. The model was empirically applied in the food industry, considering a family of potato chips products. From the collected data, a demand forecast was carried out for a later realization of the aggregate planning, using the Holt–Winters forecast model. Before modeling, the new energy demand was calculated, and finally, the model solution verification was performed. In the case study, after application, it was possible to reduce two workers and a cost reduction of R$ 14,288.00. Moreover, the proposal managed to define a power demand that minimized the costs of electric energy and the total costs of the aggregate production planning.

Plasmonic photonic crystal fiber sensor for optical partial discharge detection

Detection of partial discharge (PD) is vital to reassure the operation reliability of high voltage (HV) electrical power systems. Optical detection methods have been developed in recent years due to their high sensitivity and immunity to electromagnetic interference. In this work, D-shaped photonic crystal fiber sensor based on surface plasmon resonance is reported for optical PD detection in HV equipment. A photochromic spirooxazine dye-doped silica sol–gel is utilized for sensing the UV radiation emitted from the PD. The sol–gel refractive index depends on the radiation intensity which affects the resonance wavelength where coupling occurs between the core and surface plasmon modes. The sensing performance is demonstrated with the help of full vectorial finite element method (FVFEM). The geometrical parameters are studied to maximize the sensor sensitivity where high sensitivity of 2.4 nm/mW.cm−2 is achieved. To the best of our knowledge, it is the first time to use a simple design of plasmonic PCF for optical PD detection.

Experimental Analysis of Wax Micro-Droplet 3D Printing Based on a High-Voltage Electric Field-Driven Jet Deposition Technology

High-voltage electric field-driven jet deposition technology is a novel high resolution micro scale 3D printing method. In this paper, a novel micro 3D printing method is proposed to fabricate wax micro-structures. The mechanism of the Taylor cone generation and droplet eject deposition was analyzed, and a high-voltage electric field-driven jet printing experimental system was developed based on the principle of forming. The effects of process parameters, such as pulse voltages, gas pressures, pulse width, pulse frequency, and movement velocity, on wax printing were investigated. The experimental results show that the increasing of pulse width and duration of pulse high voltage increased at the same pulse frequency, resulting in the micro-droplet diameter being increased. The deposited droplet underwent a process of spreading, shrinking, and solidifying. The local remelting and bonding were acquired between the contact surfaces of the adjacent deposited droplets. According to the experiment results, a horizontal line and a vertical micro-column were fabricated by adjusting the process parameters; their size deviation was controlled within 2%. This research shows that it is feasible to fabricate the micro-scale wax structure using high-voltage electric field-driven jet deposition technology.

Simulation and Modelling of Transient Electric Fields in HVDC Insulation Systems Based on Polarization Current Measurements

Simulating and modelling electric field dynamics in the insulation of medium- and high-voltage DC electrical systems is needed to support insulation design optimization and to evaluate the impact of voltage transients on ageing mechanisms and insulation reliability. In order to perform accurate simulations, appropriate physical models must be adopted for the insulating material properties, particularly conductivity, which drives the electric field in a steady-state condition and contributes to determining the field behavior during voltage and load transients. In order to model insulation conductivity, polarization, and conduction, mechanisms must be inferred through charging and discharging current measurements, generally performed at different values of electric field and temperatures in flat specimens of the material under study. In general, both mechanisms are present, but one of them may be predominant with respect to the other depending on type of material. In this paper, we showed that models based on predominant polarization mechanisms were suitable to describe impregnated paper, but not polymers used for HV and MV DC insulation. In the latter case, indeed, trapping–detrapping and conduction phenomena were predominant compared to polarization, thus conductivity models had to be considered, in addition to or as a replacement of the polarization model, in order to carry out proper electric field simulations.

Design of Distributed Substation High Voltage Electrical Equipment Online Monitoring System Based on Image Segmentation Technology

As an important support mechanism for real-time monitoring and display of system frequency, harmonic voltage, harmonic current, three-phase voltage unbalance, voltage fluctuation and flicker, true power factor and other power quality parameters specified in national standard, especially for fast and accurate data processing and improving test frequency and level, the online monitoring of substation is an important support mechanism for real-time monitoring and display of system frequency, harmonic voltage, harmonic current, three-phase voltage unbalance, voltage fluctuation and flicker, true power factor and other power quality parameters specified in national standard. The research of distributed substation high voltage electrical equipment online system based on image segmentation has important practical value. However, the design system of the online monitoring network of some substation electrical equipment can not effectively follow the development needs of society and industry, and there is an urgent need for effective reform. Based on this, this paper first analyzes the problems existing in the design system construction of online monitoring network of distributed substation electrical equipment, and then gives the construction strategy of online monitoring system of high voltage electrical equipment in view of these problems.

Effects of ultrahigh permittivity ceramic on water freezing by high voltage electric field-assisted freezing system

• High voltage electric field-assisted freezing (HVEFF) on water sample was studied. • Ultra-high permittivity ceramic (UHPC) was used for the 1 st time in the freezing. • Decreasing percentage of supercooling degree was 90.3% under UHPC-HVEFF at 9 kV. • UHPC greatly improved water freezing performance when integrated to HVEFF. • UHPC possessed potentials for enlarging the sample-treating capacity of HVEFF. To investigate the effect of ultra-high permittivity ceramic (UHPC) on water freezing, a UHPC-based high voltage electric field-assisted freezing system (UHPC-HVEFF) and a low permittivity acrylic-based high voltage electric field-assisted freezing system (LPA-HVEFF) were developed. The freezing behaviours of water under UHPC-HVEFF and LPA-HVEFF at 0, 3, 6, 9 kV were comparatively studied. Hierarchical cluster analysis (HCA) was used to visualize the difference between UHPC-HVEFF and LPA-HVEFF. COMSOL was used to simulate the distribution of electric field strength in the water sample under HVEF. It was found that the decreasing percentage of the supercooling degree of the water reached 34.9%, 89.2% and 90.3% under UHPC-HVEFF at 3, 6 and 9 kV, respectively, whereas those were only 2.40%, 10.4% and 24.6% under LPA-HVEFF at 3, 6 and 9 kV, respectively. Results from the simulation indicated that the electric field strength in the water under UHPC-HVEFF was on average 11.7-7.5 times that of LPA-HVEFF, thus contributing to the high freezing efficiency of UHPC-HVEFF. This study indicated that UHPC possessed great potential to increase the sample-treating capacity of HVEF-assisted freezing system.

Novel high voltage polymer insulators using computational and data-driven techniques.

One of the key bottlenecks in the development of high voltage electrical systems is the identification of suitable insulating materials capable of supporting high voltages. Under high voltage scenarios, conventional polymer based insulators, which are one of the popular choices of insulators, suffer from the drawback of space charge accumulation, which leads to degradation in desirable electronic properties and facilitates dielectric breakdown. In this work, we aid the development of novel polymers for high voltage insulation applications by enabling the rapid prediction of properties that are correlated with dielectric breakdown, i.e.,the bandgap (Egap) of the polymer and electron injection barrier (Φe) at the electrode-insulator interface. To accomplish this, density functional theory based methods are used to develop large, chemically diverse datasets of Φe and Egap. The deviation of the computed properties from experimental observations is addressed using a statistical technique called Bayesian calibration. Furthermore, to enable rapid estimation of these properties for a large set of polymers, machine learning models are developed using the created dataset. These models are further used to predict Egap and Φe for a set of 13k previously known polymers. Polymers with high values of these properties are selected as potential high voltage insulators and are recommended for synthesis. Finally, the models developed here are deployed at www.polymergenome.org to enable the community use.

Investigation on the Work Efficiency of the LC Passive Harmonic Filter Chosen Topologies

The use of passive harmonic filters (PHFs) in an electrical system is in most cases for the fundamental harmonic reactive power compensation and harmonics mitigation. In comparison to other filters applied to improve the power quality, such as the shunt active power filter or hybrid active power filter, their main advantages are the low investment costs and easy applicability in low-, medium-, and high-voltage electrical systems. However, their installation demands a deep analysis of the electrical system as well as a thorough knowledge of the topology to be installed. Their work efficiency is influenced by the parameters of the electrical system (grid, load, and filter itself) which must be well-known before installation. The aim of this paper is to present an investigation on the work efficiency of the LC passive harmonic filter chosen topologies. The PHFs are investigated in the frequency domain through their impedance versus frequency characteristics as well as in the time domain through an electrical system. A comparative study between filters is also considered. The investigations on the case examples of PHFs are based on simulations and some laboratory studies are also presented.

Analysis of the Possibility of Ice Melting Intensity Monitoring by Direct Current in High-Voltage Electrical Systems

The Rostov nuclear power plant is the largest energy center in the South of Russia. Electricity from the nuclear power plant is transmitted to nodal substations across the territory of the Southern region, the climatic conditions of which contribute to the formation of ice deposits on power lines, this determines the urgency of the problem of ice melting. Existing systems for early detection of ice and melting it on wires of 110-500 kV overhead lines allow preventing wire breakage and destruction of supports. In modern methods ice melting is performed with alternating and direct current using special transformers and rectifiers with a melting voltage of 10 kV and a melting current of up to 3600 A, currents and voltages to prevent overheating of contacts in melting circuits and compliance with melting parameters. In circuits using direct current, there is no reliable method for controlling its magnitude. The paper considers the possibility of using a fiber-optic current sensor with a measurement range from 1 to 3600 A.

Field Grading Composites Tailored by Electrophoresis—Part 2: Permittivity Gradient in Non-Uniform Electric Field

A series of three articles present an innovative way to build advanced functionally graded materials (FGM) based on polymer/ceramic composites tailored by electrophoresis from the process principle to their field grading application in power electronics. In this Part 2, it was studied the impact of a non-uniform electric field on the high-k SrTiO3 particle organization within an epoxy matrix. In that purpose, DBC substrates with sharp metallization tracks were used to generate a strong electric field divergence. This non-uniform field has been used to organize the particles around the field reinforcement regions during the electrophoresis process. It was discovered that the particles self-arrange into a conformal composite FGM layer that presents a local permittivity gradient: the highest ε being located around the electric field peak areas. This new process could be used to selectively `heal' the electric field-induced weaknesses of any high voltage electrical system by using its own design.

STUDY AND PERFORMANCE OF PARTIAL DISCHARGE OF MODEL FOR DIFFERENT TYPE INSULATION MATERIALS WITH CAPACITANCE VALUE

The properties of the insulating material must be the best to avoid failure of electrical equipment. Partial discharges act as electrical sparks that occur within insulation and the high-voltage electrical system. The different types of voltage and current pulses are produced, which last for a very short time. Partial discharge is taking place in high voltage power equipment such as cables, transmission lines and transformers, etc.

A REVIEW OF STUDY AND ANALYSIS OF PARTIAL DISCHARGE FOR DIFFERENT INSULATION MATERIALS WITH CAPACITANCE VALUE

In the high voltage (HV) electrical power system, a variety of solid, liquid and gaseous materials are used for insulation purposes to protect incipient faults within the HV power equipment. Among these, solid insulation is widely used for high voltage equipment in high voltage power systems. Most insulation materials are not perfect in all respects and always contain some impurities. In high voltage (HV) electrical equipment, the quality of the insulation plays a very important role. Continued growth in the power system has provided the opportunity to protect equipment for healthy operation throughout its useful life.

Experimental Study on Pressure Wave Characteristics of High-Voltage Discharge in Water With Hemispherical Electrodes

High-voltage pulse discharge in water is a promising technology to enhance the permeability of coal seam and rock mass by generating fractures within them. With the aim of improving the stability and efficiency of this technology, a high voltage electric pulse experiment system was constructed. The discharge electrodes in the experiment was hemispherical. The positive and negative electrodes were arranged on the same axis with adjustable spacing. Five sets of experiments were undertaken with the electrode spacing of 1mm, 2mm, 3mm, 4mm, and 5mm, respectively. In the experiments, an oscilloscope was used to analyze the voltage, current, and pressure wave signals. The experimental results of two typical voltage-current curves indicate that the peak pressure of plasma shock wave follows a parabolic trend with the electrode spacing, and there is an optimal electrode spacing for a given discharge voltage. The peak pressure of plasma shock wave tends to increase linearly with the increase of discharge voltage. The greater the electrode spacing, the greater the sensitivity of shock wave peak pressure to the discharge voltage. The shock wave peak pressure sensitivity of 5 mm discharge spacing is 4.7 times that of 1 mm discharge spacing. The experimental results for the voltages of 9 kV, 12 kV, and 24 kV with the optimal electrode spacing show that a power function is the best fit for the attenuation of the peak pressure of shock wave with its propagation distance.

Is the Utility Transmission Syndicate Forever?

Is the Utility Transmission Syndicate Forever?

High voltage electric power supply system with contactless power take-off

Autonomous power supplies of light marking, monitoring, relay protection and emergency control systems of digital high voltage networks are considered, in particular, capacitive power take-offs from high-voltage three-phase power lines with voltage of 110 and 220 kV. Energy is collected in the immediate vicinity of the equipment, ensuring its operation without laying a separate power supply network and with minimal human involvement. The results of the analysis show a rather high technical and economic efficiency of the considered power supply system.

Ionospheric drag for accelerated deorbit from upper low earth orbit

Orbit debris mitigation restrictions placed on the growing number of miniaturised spacecraft often constrain their operational altitudes to less than approximately 600km where drag accelerations are sufficient to deorbit the spacecraft within 25 year guidelines. Operation at higher, Low Earth Orbit (LEO) altitudes often necessitates active measures to deorbit miniaturised spacecraft such as propulsion systems. However, the inclusion of propulsion systems is not always desirable because of the added cost and complexity. This work investigates the feasibility of ionospheric drag, the component of drag caused by an electrically charged body’s exchange of momentum with the ionosphere, to accelerate the deorbit of miniaturised spacecraft in high LEO (600–1000 km altitude). This work studies how actively charging the surface of a miniaturised satellite in high LEO may enhance the overall magnitude of the drag acceleration, due to the ionospheric drag, acting to deorbit the spacecraft. This is achieved using surrogate models of the charged drag coefficient, as a function of plasma scaling parameters, generated by Particle-in-Cell simulations. The charged drag coefficient surrogate model is incorporated into an orbit propagator where deorbit times are predicted over various orbital and vehicular initial conditions. Results suggest that the magnitude of ionospheric drag can be an order of magnitude larger than the neutral drag at 850 km altitude compared to approximately half the magnitude of neutral drag at 500 km altitude. Therefore, ionospheric drag is relatively more efficient at deorbiting spacecraft at high LEO compared to neutral drag. Additionally, the magnitude of ionospheric drag is tailorable based on changes in the electrical surface potential of the satellite relative to a quasi-neutral free-stream plasma. The primary payload of many miniaturised spacecraft often require high-voltage electrical systems. These same electrical systems could conceivably be utilised to generate ionospheric drag via surface charging, at the end of the mission-life, at little additional cost or system complexity. Thus, the implications of this work include the possible uncovering of a simple mechanism for deorbiting miniaturised spacecraft from high LEO altitudes for compliance with orbit debris mitigation guidelines.