Extreme High Voltage Research Articles

Characterization and novel application of power over fiber for electronics in a harsh environment

Power-over-Fiber (PoF) technology has been used extensively in settings where high voltages require isolation from ground. In a novel application of PoF, power is provided to photon detector modules located on a surface at ∼ 300 kV with respect to ground in the planned DUNE experiment. In cryogenic environments, PoF offers a reliable means of power transmission, leveraging optical fibers to transfer optical power. PoF technology excels in maintaining low noise levels when delivering power to sensitive electronic systems operating in extreme temperatures and high voltage environments. This paper presents the R&D effort of PoF in extreme conditions and underscores its capacity to revolutionize power delivery and management in critical applications, offering a dependable solution with low noise, optimal efficiency (∼ 51%), and superior isolation.

Superjunction Reliability Analysis Under Extreme High Positive and Negative Gate Voltage Stress

High gate stress test is an extremely important part of power device reliability test. On this basis, a 650 V super junction device is designed and fabricated, conventional stress test including high temperature gate bias (HTGB), high temperature reverse bias (HTRB) test results show that the device possess good reliability. The degradation of performance parameters under extreme high gate stress (including positive and negative) and the corresponding mechanism is further studied. It is found that the main performance parameters of superjunction MOSFET (SJ-MOSFET) will change significantly when the gate voltage stress is greater than 70 V. Under the positive high gate voltage stress, the threshold voltage decreases significantly. Under the negative high gate voltage stress, the threshold voltage also shifted to the left. Comparing the device under the same value of positive and negative high gate stress, it is found that the degradation degree of the device under positive stress is far greater than that under negative stress. Theoretical analysis combined with experimental data believes that the two degradation mechanisms are different. For positive stress, tunneling electrons collide on their way to the gate electrode creating electron–hole pairs, and the holes are captured by traps. But for negative gate voltage, holes tunnel and serve as extra gate positive charge directly. The electron injection efficiency is much higher than hole injection efficiency. Besides, the n-type region is larger at the bottom of the gate. Simultaneously, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{C}$</tex-math> </inline-formula> – <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\textit{V}$</tex-math> </inline-formula> measurement is also taken to prove the hypothesis.

Unbalanced currents of EHV multi-circuit lines and coordination of zero-sequence overcurrent relayings

With features of large transmission capability and high utilization efficiency of transmission corridor, multi-circuit transmission lines sharing tower or corridor are widely applied in extremely high voltage (EHV) systems. However, mal-operation of zero-sequence overcurrent relaying for multi-circuit transmission lines could occur, and this paper is focused to solve this problem. Overview of typical multi-circuits transmission lines, including phase arrangement and erection form, are introduced first. Then, simulation model of a typical 500 kV triple-circuit transmission line in real project is established in Power Systems Computer Aided Design (PSCAD), and it is verified by real record data provided by power utility in China. By using this simulation model, factors on current unbalances are discussed in detail, and the simulation results have shown that mal-operation of zero-sequence overcurrent relaying is caused by large unbalanced current in normal operation and under faults. Consequently, a lateral coordination scheme for zero-sequence overcurrent relayings among multi-circuit lines is proposed to avoid the mal-operation caused by unbalanced current to the greatest extent without receiving samples from remote end or adjacent circuits, and the reliability of protective relaying is improved significantly.

Reliability limitations from crystal defects in thick GaN epitaxial layers

The vertical power switching devices made from GaN and related nitride semiconductors contain a high density of crystal defects, especially in the thick epitaxial drift layers. Most of these defects are present initially in starting wafers and some are generated during device processing. There is little conclusive evidence so far on the exact role that the crystal defects play on device performance, manufacturing yield, and more importantly, long-term field-reliability especially when devices are operating under extreme stressful high voltage environments. This paper provides the progress of characterization of thick GaN power semiconductor material epitaxial layers and the potential impact crystal defects may have on high-density power switching electronics. The investigation also presents simulated results of the electric field distribution through thick epitaxial (greater than 10 mm) region.

Identification of Corrosion Degree for Grounded Screen of Extra High Voltage Transmission Line in Coastal Area Based on Infrared Thermal Image

Yao, N.; Wu, X., and Cai, Y., 2018. Identification of corrosion degree for grounded screen of extra high voltage transmission line in coastal area based on infrared thermal image. In: Liu, Z.L. and Mi, C. (eds.), Advances in Sustainable Port and Ocean Engineering. Journal of Coastal Research, Special Issue No. 83, pp. 124–128. Coconut Creek (Florida), ISSN 0749-0208.In the traditional recognition methods of corrosion degree of grounding grid of extreme high voltage transmission line, the noise in the infrared thermal images causes the inaccurate corrosion position and the large recognition error. Therefore, the recognition method of corrosion degree based on the infrared thermal image was proposed. Through the color histogram method, the color coherence vector method and the color correlogram method, the extraction of corrosion area characteristics in grounding grid image of extreme high voltage transmission line was realized. On this basis, HSI color space conversion was used to obtain the infrared image edge information. The median filter was used to preserve the advantage of edge information. The gradient method was used to extract the highest temperature area, realizing the identification of corrosion area of grounding grid of extreme high voltage transmission line. Experimental results show that the proposed method can accurately locate the corrosion area. It has the high recognition accuracy.

Study on Factors Affecting Residual Magnetism of Phase Selection of Extreme High Voltage Transformer and Its Calculation Method

As one of the core components in the extreme high voltage power grid, the extreme high voltage transformer has a large rated capacity, and the level of magnetizing inrush current generated by the air-to-air transformer is high. At the same time, a large amount of harmonics are injected into the power grid. In severe cases, a long duration and a slow decay can be generated. The voltage has an adverse effect on the near-area grid and equipment (especially power electronics). In order to further improve the safety and reliability of systems and equipment, effective measures need to be taken to suppress them. At present, the measures that can be used to limit the main transformer closing current include the circuit breaker installation closing resistor and the phase selection closing technology. However, since the closing resistance does not exceed 10 ms, it limits the main transformer closing excitation current, harmonics and over The effect of voltage is relatively limited, and the conventional phase-selection closing technology cannot consider the influence of transformer remanence, and its limiting effect is also not ideal. Foreign research and the use of phase-selection closing technology that takes residual magnetism in some ultra-high-pressure projects to solve the problem of air-to-air inrush current has gained some experience. In theory, this measure is expected to solve the extreme high voltage large-capacity transformer very ideally. Inrush current, harmonics, waveform distortion and overvoltage caused by closing. In this paper, the influencing factors of remanence of extreme high voltage transformers in phase-selective switching technology are studied. According to the research results, the specific scheme of voltage integral to measure residual magnetism is established.

Остаточные напряжения как возможная причина повреждения оборудования и риска для персонала при отключении воздушных линий электропередачи. Часть 1

To prevent substation equipment damage and to ensure safety of substation personnel under high voltage and extremely high voltage (EHV) overhead transmission line (TL) outage on the example of 500 kV TL outage voltages between switchable phase switch contacts are calculated. It is shown that under operating in the idle mode EHV TL outage, after arc clearing between switch contact connected to the phase at TL beginning and earth aperiodic voltage with the highest value exceeding the peak value of nominal phase voltage is created.The switch contact connected to the mains voltage, relative to the ground remains periodic nominal phase voltage. The resulting voltage between open contacts of the switch becomes aperiodic shifted periodic voltage with highest value exceeding the double peak value of nominal phase voltage that can cause breakdown of the switch. If there is a break switch phase, it will light the arc and switch under arc will go idle mode operating current, the voltage will recover to idle mode value, the current will stop, the arc goes out, aperiodic voltage will appear, etc. Such a process in a closed cycle can last a long time. Thus, output voltages high values can cause breakdown along the switches surface, damage to switches and health risk factor for the staff performing the bypass substation.

Method for accurately measuring the power‐frequency parameters of EHV/UHV transmission lines

Power-frequency parameters of long-distance extreme-high-voltage (EHV) and ultra-high-voltage (UHV) transmission lines are the basis of power system modelling and analysis, but these parameters are especially difficult to accurately measure due to the reactance-dominated nature and strong external interference. An accurate power-frequency parameter measurement approach is proposed in this study. The idea is to utilise frequency response curve to indirectly extrapolate transmission line parameters at power frequency. As no direct measurement is conducted at power frequency, the potential power-frequency interference is avoided. A resonance-based measurement method is employed to eliminate the effect of large impedance phase angle of EHV/UHV systems and identify positive- and zero-sequence resistance with enhanced accuracy. In order to validate the effectiveness of the proposed approach, a prototype instrument was developed and used to measure power-frequency parameters of a scale-down laboratory transmission line system. Comparative results confirmed the accuracy priority of the proposed approach over existing power-frequency measurement methods. In addition, the anti-interference performance in terms of the impact of the parallel in-service transmission line also indicates the proposed approach is more advantageous as it has lower capacity requirement on the measurement device.

Impact of the EHV Power System on Geomagnetically Induced Currents in the UHV Power System

Earlier calculations of geomagnetically induced currents (GICs) in Chinese power grids have mainly concentrated on the highest voltage-level system whose geomagnetic risk is considered to be the largest, thus ignoring secondary voltage-level systems. With the 1000-kV system being newly added to China's power system, it is significant to figure out the interaction between GIC in the 500 kV [extremely high voltage (EHV)] system and GIC in the 1000 kV [ultra-high voltage (UHV)] system. Based on the North China-Central China-East China Power Grids, this paper establishes a single-voltage grid by only considering the 1000-kV system and a dual-voltage grid by considering the 1000- and 500-kV systems and investigates GIC in these two grids by developing their GIC “Full-node models.” The impact of the 500-kV system on GIC in the 1000-kV system is analyzed. GIC risks in the UHV and EHV systems are assessed by comparing calculated GIC data with monitored values of GIC. The results show that the impact of the 500-kV system on GIC in the 1000-kV system is obvious, both the EHV and the UHV grid have a high GIC risk. So calculating GIC in the UHV system and in the EHV system should utilize GIC modeling methods for multivoltage power grids.

Statistical Distribution of Energization Overvoltages of EHV Cables

Statistical distributions of switching overvoltages have been used for decades for the determination of insulation levels of extremely high voltage (EHV) systems. Existing statistical distributions obtained in the 1970s are for overhead lines, and statistical distributions of switching overvoltages of EHV cables are not available to date. This paper derives the statistical distribution of energization overvoltages of EHV cables. Through the comparison of the statistical distributions of EHV cables and overhead lines, it has been found that line energization overvoltages on the cables are lower than those on the overhead lines with respect to maximum, 2%, and mean values. As the minimum value is almost at the same level, standard deviations are smaller for the cables. The obtained statistical distributions in this paper are of a great importance in considering insulation levels of cable systems.

Derivation of Theoretical Formulas of the Frequency Component Contained in the Overvoltage Related to Long EHV Cables

Recent studies of long extremely high-voltage (EHV) cables show the importance of performing temporary overvoltage analyses. As the switching of EHV cables can trigger temporary overvoltages, it is important to find the dominant frequency component contained in the switching overvoltages of these cables. Since there are no theoretical formulas to find the dominant frequency, it is generally found by means of time domain simulations or frequency scans. The derivation of theoretical formulas has been desired as the formulas would be useful in verifying the results of time-domain simulations or frequency scans. In addition, the formulas could eliminate the necessity of building simulation models of some network components. In order to address this need, this paper derives theoretical formulas to find the dominant frequency in long cable energization overvoltages. The accuracy and practical usefulness of the formulas are confirmed by comparing them with the results of time-domain simulations.

Analysis of Lightning Shielding Failure for 500-kV Overhead Transmission Lines Based on an Improved Leader Progression Model

An improved leader progression model (LPM) for analyzing the shielding failure performance of overhead transmission lines is established, and implemented in calculating the shielding failure rate and shielding failure flashover rate of 500-kV transmission lines. This paper discusses the inadequate parts of the existing LPM and presents improvements to meliorate the model for applications on extremely high voltage (EHV) transmission lines. The model is improved mainly in three aspects: 1) the background electric field produced by the lightning cloud is simulated by multielectrode configuration, 2) different inception criteria of upward leaders for shielding wires and phase conductors are chosen, and 3) the impact of power frequency operating voltage on the shielding failure flashover rate is considered. The improved model is applied to analyze the shielding failure performance of 500-kV transmission lines in China considering the flat and hilly terrain conditions. The shielding failure flashover rates by existing models and the improved model are calculated and compared with the operating data of 500-kV transmission lines. It is shown that the predicted result of the improved LPM is in accordance with the operating experience. The improved model is suitable for the lightning shielding assessment and applicable in the design of EHVAC transmission lines.

Steiner Tree 이론을 이용한 우편물 교환센터인 최적 워치선정

Faster, safer and cheaper mailing of the postal matter is essential for surviving in the competitive market of home-delivery service. In the past, the domestic delivery business has been nu by only a few number of companies. But more and more number of companies including medium size ones are participating in the business, and the competition is getting severe. This paper proposes a method to select the optimal location of mail distribution centers that minimally connect the local mail centers of some major cities in Korea using the Steiner Tree theory, which is about connecting a finite number of points with a minimal length of paths and has been used in the distribution system optimization and optimal routing of the transmission lines of the electric power system. By using Steiner Tree theory in finding the best location of the postal delivery hub, we may expect the reduction of transportation cost and the increase of profit, resulting in acquiring the superior position in the competitive delivery business. It is expected that we may use the Steiner Tree theory in finding the best location of the electric power substation for the nott higher EHV(extreme high voltage) transmission network.

高電圧太陽電池アレイ

In order to manage gigantic power of SSPS (Space Solar Power System) efficiently, use of extreme high voltage is necessary unless we minimize the transmission distance by employing a sandwich type of generator/transmitter panel. For 1 GW-class SSPS, the power transmission/generation voltage of 10 kV is necessary to keep the cable mass below a few hundred tons. To realize high voltage photovoltaic power generation, arcing caused by environmental interaction must be overcome. Three issues are reviewed. The first is degradation of solar cell performance due to repetitive arcing resulted from surface charging in GEO. The second is sustained arc phenomenon that may lead to catastrophic loss of significant portion of the total power. The third is micrometeoroid or space debris impact and resulting sustained arc. A design of high voltage solar array is proposed to prevent solar cell degradation due to repeated trigger arcs and sustained arc.

Magnetoelectric coupling, efficiency, and voltage gain effect in piezoelectric-piezomagnetic laminate composites

The magnetoelectric (ME) effect of piezoelectric-magnetostrictive laminate composites, which is a product tensor, has been studied. Based on piezoelectric and piezomagnetic constituent equations, the longitudinal-mode vibration and equivalent circuits have been derived. The effective magnetoelectric coupling coefficient, voltage-gain, and output efficiency have been determined. Our results show: (i) that there is an extreme high voltage gain effect of >260 under resonance drive: the induced ME voltage is much higher than the input voltage to the coils for magnetic excitation; (ii) that there is an optimum ratio of the piezoelectric to piezomagnetic layer thicknesses, which results in maximum effective magnetoelectric coupling; and (iii) that the maximum output efficiency of magnetoelectric laminate at resonance drive is ∼98%, if eddy currents are neglected. This high ME voltage gain effect offers potential for power transformer applications.

Transient positional protection of transmission lines using complex wavelets analysis

This paper presents a new high-speed protection scheme, transient positional protection (TPP), for power transmission lines. This scheme is developed using complex wavelet analysis, based on the concept of transient-based protection (TBP), in which the fault-generated high-frequency transient signals contained in the primary voltages are utilized to detect fault position according to their relative travelling time and polarities. Combined information (CI) is obtained from complex wavelet coefficients to extract and localize a band of specified high-frequency components propagating along the transmission line. A typical 400 kV extremely high voltage (EHV) transmission system has been simulated by PSCAD/EMTDC to evaluate the scheme. The simulation results show that this scheme is capable of providing correct responses under various system configurations and fault conditions.

EHV series capacitor banks: a new approach to platform to grounds signalling, relay protection and supervision

A method for platform-to-ground signaling, relay protection, and supervision of EHV (extremely high voltage) series capacitor banks is presented. The system comprises optical current transducers, optical fiber system, interface unit, and microprocessor-based protection supervision and control equipment located in the control room. The optical current transducer, located at high potential, does not need its own power supply, since it is powered with light from ground level via the optical fiber system. The microprocessor-based protection and supervision system comprises all the protection functions required for the series capacitor bank. In addition, it includes a number of supervision and logging functions. Typical applications of the new system, besides EHV series capacitor banks, are for current measurements in substations and other EHV installations. Operating experience from an unattended 400 kV pilot installation was excellent.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Validated techniques for modeling shell-form EHV transformers

An EHV (extremely high voltage) shelf-form autotransformer has been thoroughly instrumented and tested for frequency response and step response. The results have been used to develop and validate computer models for predicting the transient behavior of transformers at the design stage. The models are based on relatively simple constant-parameter circuit models. The procedures have been applied to other shell-form EHV transformers with similar results: the dominant response in the 8 to 20 kHz range is easily reproduced, while the model sometimes produces some spurious higher-frequency oscillations. The discrepancies may be a limitation imposed by the constant-parameter circuit model and can frequently be eliminated by lumping two or three coils together. A streamlined, user-friendly impulse calculation program has been developed for a PC, yielding execution times acceptable for the design environment.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>