scholarly journals Interruption of Medium-Voltage Direct-Currents by Seperation of Contact Elements in Mineral Oil Using an Ultra Fast Electro-Magnetic Actuator

2019 ◽  
Vol 6 (1) ◽  
pp. 73-77
Author(s):  
S. Jugelt ◽  
C. Leu
Keyword(s):  
Electrical Energy ◽  
Mineral Oil ◽  
Magnetic Actuator ◽  
Rapid Separation ◽  
Zero Crossing ◽  
Medium Voltage ◽  
Dielectric Liquids ◽  
Electro Magnetic ◽  
Current Zero ◽  
Energy Grid

The increasing usage of medium-voltage direct-current in upcoming electrical energy grid topologies requests novel solutions for MVDC switching. The interruption of direct-currents is accomplished by enforcing a current zero crossing by adequate means and preventing reignition due to the recovering dc voltage. This paper evaluates the rapid separation of the contact elements in mineral oil leading to a liquid flow around the contact elements and the switching arc. The energy turnover of dielectric liquids interacting with an electric arc is considerably higher leading to heavily increased arc voltages compared to dielectric gases. This paper confirms results of earlier publications and carries them further towards a possible usage in an MVDC switching or protection device. Thus a contact arrangement surrounded by mineral oil in combination with an ultra fast electro-magnetic actuator is introduced and performed measurements are discussed.

Reduction of the Low Voltage Substation Constraints by Inserting Photovoltaic Systems in Underserved Areas

2019 ◽  
Vol 12 (2) ◽  
pp. 105-112
Author(s):  
Benbouza Naima ◽  
Benfarhi Louiza ◽  
Azoui Boubekeur
Keyword(s):  
Low Voltage ◽  
Voltage Drop ◽  
Electrical Energy ◽  
Utilization Rate ◽  
Photovoltaic Systems ◽  
Voltage Distribution ◽  
Medium Voltage ◽  
Pv Systems ◽  
Transformer Substation ◽  
Load Pattern

Background: The improvement of the voltage in power lines and the respect of the low voltage distribution transformer substations constraints (Transformer utilization rate and Voltage drop) are possible by several means: reinforcement of conductor sections, installation of new MV / LV substations (Medium Voltage (MV), Low Voltage (LV)), etc. Methods: Connection of mini-photovoltaic systems (PV) to the network, or to consumers in underserved areas, is a well-adopted solution to solve the problem of voltage drop and lighten the substation transformer, and at the same time provide clean electrical energy. PV systems can therefore contribute to this solution since they produce energy at the deficit site. Results: This paper presents the improvement of transformer substation constraints, supplying an end of low voltage electrical line, by inserting photovoltaic systems at underserved subscribers. Conclusion: This study is applied to a typical load pattern, specified to the consumers region.

Optimized Non-Dead-Time Control of Inverter with Two-Phase Modulated SVPWM

2012 ◽  
Vol 562-564 ◽  
pp. 1531-1536
Author(s):  
Ming Xing Zhu ◽  
Jing Bo Shi
Keyword(s):  
Control Strategy ◽  
Pulse Width Modulation ◽  
Dead Time ◽  
Control Method ◽  
Short Circuit ◽  
Two Phase ◽  
Zero Crossing ◽  
Time Control ◽  
Bus Voltage ◽  
Current Zero

In the inverter control system, two-phase modulated space vector pulse width modulation (SVPWM) algorithm has the advantages of minimum switch loss and higher utilization of direct current (DC) bus voltage. Non-dead-time control strategy can eliminate the problems of the dead time effects. But the traditional non-dead-time control strategy heavily depends on the current zero-crossing detection, which may cause the output voltage distortion or even a short circuit. Based on the analysis of the reason for the distortion, a new optimized non-dead-time control method is proposed. Two methods for the detection of the overlapping area are enumerated. The conclusions are confirmed by the simulation results with MATLAB/ SIMULINK.

PFC Converter with Improved Input Current Zero-crossing Distortion

2017 ◽  
Vol 45 (12) ◽  
pp. 1329-1338 ◽  
Author(s):  
Kuo-Ing Hwu ◽  
Wen-Zhuang Jiang
Keyword(s):  
Input Current ◽  
Zero Crossing ◽  
Current Zero

scholarly journals Operation Modes of HV/MV Substations

2009 ◽  
Vol 25 (25) ◽  
pp. 81-86
Author(s):  
Josifs Survilo ◽  
Antons Kutjuns
Keyword(s):  
High Voltage ◽  
Low Voltage ◽  
Warm Season ◽  
Electrical Energy ◽  
Cold Season ◽  
Power Losses ◽  
Medium Voltage ◽  
The Third ◽  
Operation Modes ◽  
Mode 3

Operation Modes of HV/MV SubstationsA distribution network consists of high voltage grid, medium voltage grid, and low voltage grid. Medium voltage grid is connected to high voltage grid via substations with HV/MV transformers. The substation may contain one, mostly two but sometimes even more transformers. Out of reliability and expenditure considerations the two transformer option prevail over others mentioned. For two transformer substation, there may be made choice out of several operation modes: 1) two (small) transformers, with rated power each over 0.7 of maximum substation load, permanently in operation; 2) one (big) transformer, with rated power over maximum substation load, permanently in operation and small transformer in constant cold reserve; 3) big transformer in operation in cold season, small transformer-in warm one. Considering transformer load losses and no load losses and observing transformer loading factor β it can be said that the mode 1) is less advantageous. The least power losses has the mode 3). There may be singled out yet three extra modes of two transformer substations: 4) two big transformers in permanent operation; 5) one big transformer permanently in operation and one such transformer in cold reserve; 6) two small transformers in operation in cold season of the year, in warm season-one small transformer on duty. At present mostly two transformers of equal power each are installed on substations and in operation is one of them, hence extra mode 5). When one transformer becomes faulty, it can be changed for smaller one and the third operation mode can be practiced. Extra mode 4) is unpractical in all aspects. The mode 6) has greater losses than the mode 3) and is not considered in detail. To prove the advantage of the third mode in sense of power losses, the notion of effective utilization time of power losses was introduced and it was proven that relative value of this quantity diminishes with loading factor β. The use of advantageous substation option would make it possible to save notable amount of electrical energy but smaller transformer lifetime of this option must be taken into account as well.

Design and Implementation of Actuator Controller for Greenhouse Control System

2014 ◽  
Vol 532 ◽  
pp. 62-69
Author(s):  
Yi Chuan Gao ◽  
Guo Chang Liu
Keyword(s):  
Control System ◽  
Short Circuit ◽  
Alternating Current ◽  
Electric Arc ◽  
Zero Crossing ◽  
Three Phase ◽  
Detection Circuit ◽  
Task Program ◽  
Current Zero ◽  
Greenhouse Control

A novel actuator controller for greenhouse control system is proposed in this paper. This controller can solve the problems existing in traditional greenhouse control system such as generating electric arc, short circuit risk, lack of communication and smart ability. We adopt five separate magnetic latching relays to control the three-phase motor. In order to prevent generating electric arc in the process of turning off relay, the alternating current zero-crossing detection circuit is designed. In software side, the relay-off task program is running in the real-time operating system, which can ensure turn-off operation at the point of alternating current zero-crossing. In addition, the controller is capable of detecting motors operation parameter and having multiple communication interfaces. Finally, we implement our controller in practice and experimental results meet the design requirements.

scholarly journals Optimization and Experimental Study of the Semi-Closed Short-Gap Arc-Extinguishing Chamber Based on a Magnetohydrodynamics Model

Energies ◽  
2018 ◽  
Vol 11 (12) ◽  
pp. 3335 ◽  
Author(s):  
Wenbin Jia ◽  
Wenxia Sima ◽  
Tao Yuan ◽  
Ming Yang ◽  
Potao Sun
Keyword(s):  
High Speed ◽  
Basic Structure ◽  
Optimization Method ◽  
Original Structure ◽  
Arc Plasma ◽  
Zero Crossing ◽  
In Series ◽  
Power Frequency ◽  
Motion Characteristics ◽  
Current Zero

The multi-chamber arc-extinguishing structure (MAS), which consists of a lot of semi-closed short-gap arc-extinguishing chambers (SSAC) in series, can be used in parallel gap lightning protection devices to improve the ability to extinguish power frequency follow current. The arc-extinguishing ability of single SSAC directly affects the arc-extinguishing performance of the whole MAS. Therefore, the arc-extinguishing performance of MAS can be improved by optimizing single SSACs. A two-dimensional model of the arc plasma in a SSAC is built based on the magneto-hydrodynamic (MHD) theory. The motion characteristics of an arc in the SSAC are simulated and analyzed. An optimization method of the SSAC structure is proposed. Finally, an impact test platform is built to verify the effectiveness of the optimized SSAC structure. Results show that the short-gap arc forms a high-speed airflow in the SSAC and the arc plasma sprays rapidly to the outlet until the arc is extinguished at its current zero-crossing point. The amplitude of airflow velocity in the optimized structure can be increased to about 8-fold the velocity in the basic structure. Experiments also show that the dissipation time of an arc in the optimized SSAC is 79.2 μs, which is much less than that in the original structure (422.4 μs).

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