Suchergebnisse

Mongolia is a landlocked country situated between two powerful neighbors Russia to the north, China to the south. Due to Mongolia's geographical positioning, the country has limited diplomatic options to showcase its power both at the global and regional levels. Thus, Mongolia was forced to initiate political and economic reforms to cope up with the post-cold war global politics. In recent times, Mongolia's unexplored and abundant natural resources are key factors of Mongolia's socio-economic development. Yet, Mongolia is often cited as an example of a "resource curse". Mongolia was unable to use its natural resources efficiently hence suffered from resource deficient economic, political, and social challenges. Mongolia's geographical location and its landlocked position between China and Russia constrained Mongolia's ambition to shift from an import-based economy to an export-oriented powerful economy in North-East Asia. However, Mongolia's natural resources, political stability, and non-alignment approach have great potential to decrease Mongolia's overdependence on imports from neighboring countries. Mongolia in the post-cold war era regime is adopting a diverse and multilateral approach. With a brief overview of the economic, political, physical challenges faced by Mongolia, the paper highlights the potential of Mongolia's energy sources.

SF6-gas is widely used in medium and high voltageswitchgear today because of its excellent insulation andcurrent interruption capabilities. However, due to itshigh global warming potential, there is a politicalpressure to replace it wherever possible, resulting in aneed for new solutions in the design of compact lowcostswitchgear. An evident response is to review andfurther develop the technologies that were promisingbefore the entry of SF6. One of these was the applicationof gas-emitting insulation materials, in a process ofablation.This paper reviews the range of commercial breakerdesigns that have taken advantage of ablation in theinterruption process from the 1930s until today. Themain designs and developments are outlined and someimportant parameters are explained, such as the steadystate ablation-dominated arc, arc quenching anddielectric recovery in the presence of ablation material.The ratings of the mentioned products, as well as morerecent experiments, indicate that there is a design limitfor simple ablation-assisted breakers at around 20 kV,but the reasons for the apparent limit are not thoroughlystudied or explained.Reviving the knowledge of ablation breakers, andcombining this with new knowledge and new toolscould prove valuable to the development of SF6-freeMV switchgear.

This paper describes the setup and characterization of a set of wideband Current-to-Voltage (C-to-V) transformers equipped with symmetrical primary windings. The objective is to use the C-to-V transformer set to calibrate digital instrument transformer (IT) accurately at power frequency and within a wider frequency range to cover power quality aspects. The errors of the 50 A and the 200 A reference current transformer (CT) were within ±10 ppm and μrad at 50 Hz. The frequency responses of the two CTs up to 12 kHz were below 0.1 % and 0.2 crad. ; The project 17IND06 Future Grid II has received funding from EMPIR Programme co-financed by the Participating States and from the European Union's Horizon 2020 research and innovation programme

The first electric low-voltage vehicles were constructed in the mid-19th century, but by the early 20th century they were progressively replacedby successors with internal combustion engines. As the consequences ofusing fossil fuels are better understood, our society is now transitioning back. The strong driving force towards electric transportation can be traced to several events and trends. The foremost of these is perhaps the rising awareness of climate change and the necessary reduction of the environmental footprint, as well associated political will for change. Alongside this, the pioneering automotive company Tesla, Inc. showed what electric cars are capable of and how to easily charge them along the road. The diesel gate unearthed in 2015, also played a major role. This transition is not without challenges, however. An electric car is expected to be reasonable priced, sustainable, environmentally friendly and electrically safe, even in case of an accident. Overnight charging at home should be possible, as well as the ability to quickly charge while in transit. While the industry has long experience with high-voltage electrical machines, the required battery technology is quite new and low-voltage in nature. Currently, the battery is the most costly part of an electric drivetrain and it has the highest environmental impact. Efficient battery use is therefore key for sustainability and a responsible consumption of the resources available. Nonetheless, most electric vehicles today use lethal high-voltage traction drives which require a considerable isolation effort and complex battery pack. Previous research results showed that a 48 V drivetrain compared to a high-voltage one, increases the drive-cycle efficiency. Hence, similar driving range can be reached with a smaller battery. This thesis provides an introduction to low-voltage, high-current, battery-powered traction drives. With the aim of increasing efficiency, safety and redundancy while reducing cost, a solution that breaks with century-old electric machine design principles is proposed and investigated. An overview and motivation to further investigate 48 V drivetrains with intrinsically safe and redundant machines is provided. The main focus of this work is the practical implementation of multi-phase low-voltage but high-current machines with integrated power electronics as well as components for a 48 V drivetrain. With this work, it is confirmed that today's MOSFETs are not the limiting factor towards low-voltage, high-current drives. In the first part of this work, two small-scale prototype machines were constructed and tested. The air-cooled, small-scale 1.2 kW proto-type reached a copper fill-factor of 0.84. The machine's low terminal-to-terminal resistance of 0.23 mΩ, including the MOSFET-based power electronics, allowed continuous driving currents up to 600 A. The resistive MOSFET losses stayed below 21 W. The second part focuses on the key components for a 48 V high-power drivetrain. A W-shaped coil for a multiphase 48 V machine with direct in-conductor cooling was designed and tested. With glycolwater, it reached a current density of 49.5 A/mm2 with 0.312 l/min flowrate. Furthermore, a reconfigurable battery pack for 48 V driving andhigh-voltage charging was investigated. ; Vid tidpunkten för disputationen var följande delarbeten opublicerade: delarbete 5 inskickat, delarbete 8 manuskript. At the time of the doctoral defence the following papers were unpublished: paper 5 submitted, paper 8 in manuscript.

Purpose. Development and evaluation, on the basis of existing ultra-high-voltage generator of pulsed voltages and currents of GINT-4 type, of the new scheme of design of its charging-discharging circuit (CDC), and creation of modernized powerful ultra-high-voltage high-current generator of GINT-2 type to form microsecond voltage pulses with amplitudes up to ±2 MV and current with amplitude up to ±150 kA in the electrical load, with electrical energy stored in its capacitive energy storage (CES) up to 1 MJ. Methodology. Fundamentals of theoretical and applied electrical engineering, electrical power engineering, electrophysical principles of high-voltage and high pulsed current engineering, fundamentals of electromagnetic compatibility (EMC), instrument engineering, high-voltage instrumentation and standardization. Results. The new scheme of design of CDC of the modernized powerful ultra-high-voltage, heavy-current generator of GINT-2 type of outdoor placement, that allows obtaining, with preservation of the main electrotechnical elemental base of existing powerful prototype generator GINT-4 (rated output voltage ±4 MV with rated electrical energy stored in CES of 1 MJ and maximal amplitude of output current pulse in electrical load up to ±75 kA) pulses of current of microsecond duration with doubled amplitude (up to ±150 kA) in the long (from 1 to 4 m length) air gap of standard two-electrode discharging «needle-plane» system, in comparison with parameters of current pulses with amplitudes up to ±75 kA that are formed in the discharging circuit of generator of GINT-4 type with the use of the analogous air discharging system, has been developed. Experimental evaluations of the developed new discharging circuit in CDC of the modernized generator of GINT-4 type has been performed in field conditions, and its advantages over the old discharging circuit in composition of CDC of generator of GINT-4 type have been shown. Calculated evaluations of rise rates of high pulsed current (HPC) in plasma channel of air spark ...