scholarly journals Experimental Assessment on Air Clearance of Multiple Valve Unit Considering Switching Impulse and DC Superimposed Switching Impulse

Energies ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2958
Author(s):  
Jae-Hong Koo ◽  
Jae-Kyu Seong ◽  
Ryul Hwang ◽  
Bang-Wook Lee
Keyword(s):  
Wave Front ◽  
High Voltage ◽  
Normal Operation ◽  
Reliable Operation ◽  
Peak Voltage ◽  
Experimental Assessment ◽  
Dielectric Characteristics ◽  
Valve Unit ◽  
Hvdc Transmission ◽  
Flashover Voltage

Multiple valve unit (MVU), which converts AC to DC and DC to AC, is one of the key elements of high voltage DC (HVDC) transmission. Therefore, the insulation design of MVU against overvoltage should be considered for the stable and reliable operation of HVDC transmission system. Especially, the air clearance of MVU should be calculated based the switching impulse, since it is fatal to MVU in terms of electrical insulation. However, the previous studies were limited to wave front, and the air clearance of the switching impulse is specified only for an ultra-high voltage (UHV) above 750 kV. As a result, it is difficult to calculate the air clearance of MVU which must endure for a switching impulse under 750 kV. In addition, when the switching impulse introduced while the MVU is in normal operation, it is superimposed to DC and creates the most severe situation, but the studies on such subjects are also insufficient. Therefore, as a fundamental step to calculate the air clearance of MVU, the dielectric characteristics of switching impulse and DC superimposed switching impulse in air have been investigated. The experiments on switching impulse showed that the critical flashover voltage was varied according to the curvature of electrode in the gap distance, up to eight times of the electrode radius. However, beyond that gap distance, the critical flashover voltage became similar, regardless of the radius of electrodes. In case of the superimposed experiment, it was performed according to DC pre-stress level and the polarities of switching impulse. The results were most severe when the positive switching impulse was superimposed on the positive DC, and the peak voltage at which flashover occurs was independent of DC pre-stress.

scholarly journals Solid-State DC Circuit Breakers and their Comparison in Modular Multilevel Converter Based-HVDC Transmission System

Electronics ◽  
2021 ◽  
Vol 10 (10) ◽  
pp. 1204
Author(s):  
Gul Ahmad Ludin ◽  
Mohammad Amin Amin ◽  
Hidehito Matayoshi ◽  
Shriram S. Rangarajan ◽  
Ashraf M. Hemeida ◽  
...  
Keyword(s):  
Solid State ◽  
High Voltage ◽  
Direct Current ◽  
Circuit Breaker ◽  
Transmission System ◽  
Simulation Software ◽  
Fault Current ◽  
Circuit Breakers ◽  
Hvdc Transmission ◽  
Dc Circuit Breakers

This paper proposes a new and surge-less solid-state direct current (DC) circuit breaker in a high-voltage direct current (HVDC) transmission system to clear the short-circuit fault. The main purpose is the fast interruption and surge-voltage and over-current suppression capability analysis of the breaker during the fault. The breaker is equipped with series insulated-gate bipolar transistor (IGBT) switches to mitigate the stress of high voltage on the switches. Instead of conventional metal oxide varistor (MOV), the resistance–capacitance freewheeling diodes branch is used to bypass the high fault current and repress the over-voltage across the circuit breaker. The topology and different operation modes of the proposed breaker are discussed. In addition, to verify the effectiveness of the proposed circuit breaker, it is compared with two other types of surge-less solid-state DC circuit breakers in terms of surge-voltage and over-current suppression. For this purpose, MATLAB Simulink simulation software is used. The system is designed for the transmission of 20 MW power over a 120 km distance where the voltage of the transmission line is 220 kV. The results show that the fault current is interrupted in a very short time and the surge-voltage and over-current across the proposed breaker are considerably reduced compared to other topologies.

scholarly journals Global experience of HVDC composite insulators in outdoor and indoor environment

2020 ◽  
Vol 59 (1) ◽  
pp. 606-618
Author(s):  
Mohammad Akbar ◽  
Basharat Mehmood
Keyword(s):  
High Voltage ◽  
Direct Current ◽  
Transmission Lines ◽  
Power Transmission ◽  
Green Energy ◽  
Attractive Alternative ◽  
Hvdc Transmission ◽  
Ceramic Insulators ◽  
High Power Transmission ◽  
Aging Performance

AbstractHigh-voltage direct current (HVDC) transmission is known as green-energy transfer technology and has recently become an attractive alternative of high-voltage alternating current (HVAC) due to its high-power transmission capability and lower power loss. Use of composite insulators on direct current (DC) transmission lines experienced rapid growth in recent years due to their high hydrophobicity and better performance in contaminated environment than conventional ceramic insulators. During their service operation on DC lines, insulators are prone to more accumulation of contaminants due to unidirectional electric field. The contaminants under wet conditions allow leakage current to flow on the insulator surface. Being organic in nature, polymeric insulators have a tendency to age under the combined effects of electrical and environmental stresses. To fully understand the long-term aging performance of DC composite insulators, a detailed survey was considered necessary. Towards that end, this paper critically summarizes worldwide experience of aging performance of composite insulators in the field as well as in laboratory conditions.

scholarly journals Operating Performance of Power Systems Integrated HVDC Solution: KonTum-GiaLai Transmission System Case Considering Penetration of Renewable Energy

2020 ◽  
Vol 18 (4.2) ◽  
pp. 32
Author(s):  
Kim Hung Le ◽  
Ngoc Thien Nam Tran ◽  
Viet Tri Nguyen ◽  
The Khanh Truong ◽  
Minh Quan Duong
Keyword(s):  
Renewable Energy ◽  
Power Systems ◽  
High Voltage ◽  
Short Circuit ◽  
Renewable Energy Sources ◽  
Transmission Efficiency ◽  
Transmission System ◽  
Large Power ◽  
Hvdc System ◽  
Hvdc Transmission

The increasing demand for electricity along with the development of distributed generators showed that improving transmission efficiency and reliability is an indispensable requirement in the operation of the power system. Advanced technologies need to be applied to modern power systems for purposes of conveying large power flows, mitigating the risk of faults. High-voltage direct current (HVDC) transmission is now considered an effective solution for investment in large-length power lines, replacing the conventional high-voltage alternative current (HVAC) transmission system, especially in period of increasing generation capacity due to the penetration of renewable energy sources. This study assesses the performance of the HVDC system on an actual power grid based on planning and improvement demands. The calculation results of power flows, power losses and short-circuit faults were investigated using ETAP software X  

Polymer Nanocomposites in High-Voltage Insulation: The Dielectric Characteristics of Doped Polypropylene

2018 ◽  
Vol 12 (2) ◽  
pp. 33-40
Author(s):  
Xiaohong Chi ◽  
Weiwang Wang ◽  
Shengtao Li ◽  
Michel Frechette ◽  
Xiaohong Zhang
Keyword(s):  
Polymer Nanocomposites ◽  
High Voltage ◽  
Dielectric Characteristics ◽  
High Voltage Insulation

scholarly journals Surface Discharge Mechanism on Epoxy Resin in Electronegative Gases and Its Application

2020 ◽  
Vol 10 (19) ◽  
pp. 6673
Author(s):  
Herie Park ◽  
Dong-Young Lim ◽  
Sungwoo Bae
Keyword(s):  
Sulfur Hexafluoride ◽  
Design Method ◽  
Surface Discharge ◽  
Uniform Field ◽  
Dielectric Characteristics ◽  
Discharge Mechanism ◽  
Dry Air ◽  
Surface Flashover ◽  
Flashover Voltage ◽  
Insulation Performance

This study presents the surface discharge characteristics of insulating gases, including sulfur hexafluoride (SF6), dry air, and N2, under a non-uniform field. Surface discharge experiments were conducted, with the gas pressure ranging from 0.1 to 0.6 MPa, on samples of epoxy dielectrics under an AC voltage. The experimental results showed that the surface insulation performance significantly improved in insulating gases possessing electronegative gases, such as SF6 and dry air. Surface flashover voltages of SF6 were saturated with an increasing pressure, compared to dry air and N2. The surface discharge mechanism is proposed to explain the improvement and saturation of dielectric characteristics of the electronegative gas in complex dielectric insulations, as well as its influence on the surface flashover voltage. As an application, an insulation design method is discussed with regards to replacing SF6 gas in high-voltage power equipment based on the knowledge of the physics behind gas discharge.

scholarly journals Dynamic Stability Improvement of Power System with VSC-HVDC Transmission

2018 ◽  
Vol 7 (3.27) ◽  
pp. 500
Author(s):  
R Vasudevan ◽  
S Ramalakshmi
Keyword(s):  
Power System ◽  
Dynamic Stability ◽  
High Voltage ◽  
Transient Stability ◽  
Reactive Power ◽  
Average Frequency ◽  
Management Approach ◽  
Communication Delays ◽  
Hvdc Transmission ◽  
Central Controller

A new management approach for the reactive-power injections of Voltage supply Converters in High Voltage DC (VSC-HVDC) multi-terminal Systems to enhance grid transient stability. A reactive-power supplementary signal is provided for each convertor. Its worth is proportional to the frequency deviation of its consequent AC bus with admiration to the weighed-average frequency of the multiterminal system stations. The hope is to extend (decrease) the magnetism torsion of generators close to those terminals during which the frequency is superior to (below) the weighed-average frequency used. The AC frequency for all VSC stations is ever more accessible regionally for synchronization functions and will be utilized by a central controller. Simulations are allotted victimization PSS/E and therefore the outcome have revealed that transient stability is enlarged victimization this approach. Since this approach uses world capability of all VSC stations, the collision of the communication delays has been analyzed, concluding that the depressing consequence is modest, for realistic latency values. 

scholarly journals Partial discharge detection for stator winding insulation of motors using artificial neural network

2018 ◽  
Vol 10 (7) ◽  
pp. 168781401878612 ◽  
Author(s):  
Yu-Tung Chen ◽  
Jui-Chien Lai ◽  
Yu-Ming Jheng ◽  
Cheng-Chien Kuo ◽  
Hong-Chan Chang
Keyword(s):  
Neural Network ◽  
Artificial Neural Network ◽  
High Voltage ◽  
Partial Discharge ◽  
Recognition Rate ◽  
Gradient Algorithm ◽  
Normal Operation ◽  
Test Models ◽  
Artificial Neural ◽  
Stator Fault

In this article, the insulation fault detection of high-voltage motors by the artificial neural network algorithm is used. The proposed method can evaluate the status of operating motor without interrupting the normal operation. According to the measurement of partial discharge information, this research establishes the relationship of stator failures and pattern features. This study uses common high-voltage motor stator fault types to experimentally produce four types of stator test models with insulation defects; these models are compared with a healthy motor model. Through the learning of the artificial neural network, the experimental results show that the artificial neural network–based stator fault diagnosis system proposed in this article has a recognition rate as high as 90% when the conjugate gradient algorithm is used, and there are 20 neurons in the hidden layer.

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