ABB Ltd

About: ABB Ltd is a company organization based out in Zurich, Switzerland. It is known for research contribution in the topics: Voltage & Signal. The organization has 6222 authors who have published 6852 publications receiving 83994 citations.

Fault Detection and Isolation in Medium-Voltage DC Microgrids: Coordination Between Supply Power Converters and Bus Contactors

Abstract: A fast and effective method for detecting and isolating faults in medium-voltage dc microgrids relies on rapid coordination between power supply converters and bus segmentizing contactors to limit currents and isolate faults without any need for fast communication between these active elements. The power converters independently enter current-limiting mode as soon as they recognize a fault condition and the segmentizing contactors autonomously decide whether or not to open based on their local interpretation of time-to-trip curves as functions of apparent circuit resistance. This method allows converters and contactors to use only local measurements when discerning whether or not to trip in order to isolate the faulted section. Simulation and experimental results show that low-impedance short-circuit faults can be isolated within 10–20 ms and the system can be reenergized within 40–60 ms. The method is effective for a wide range of fault and system configurations, and that range can likely be expanded by applying additional discrimination methods.

HVDC WITH VOLTAGE SOURCE CONVERTERS AND EXTRUDED CABLES FOR UP TO ±300 kV AND 1000 MW

Abstract: SUMMARY VSC HVDC systems have a lot of interesting properties of which the most interesting is the possibility to make connections in or between networks by low weight extruded cables. These connections can be made at a cost that can even be comparable with overhead ac lines. In addition to full power flow control in both directions, the VSC HVDC systems can prevent fault propagation, increase low frequency stability, reduce network losses and increase voltage stability. These attractive features open interesting markets and applications where power shall be transported over long distances at large depths under demanding circumstances and where network stability, safety and reliability are of the highest priority. Today a maximum power handling of the system of at least 1000 MW at ±300 kV dc is attainable, thanks to synchronized development in four major technical areas: IGBT valves, DC cable system, main circuit of converter station and control system. This paper presents the development in those four areas. The VSC valves have increased current handling, lower losses, better cooling and more even voltage sharing so they may be built for drastically higher power rating than previously. A new larger presspack IGBT gives higher converter current handling. The cable system has been expanded in voltage and laying depth. Robust flexible and stiff joints have been developed for the polymeric extruded cables. Testing has proved 300 kVdc capability of the cable system and laying depth larger than 2000 m. The converter main circuit has been modified for greater simplicity, lower investment cost and lower losses. The control system has been developed to be more robust and have more control functionalities including black-start control which can provide full support during grid restoration processes.

High-voltage bushing

Abstract: The high-voltage bushing (1) has a conductor (2) and a core (3) surrounding the conductor (2), wherein the core (3) comprises a sheet-like spacer(4), which spacer (4) is impregnated with an electrically insulating matrix material (6) It is characterized in that the spacer (4) has a multitude of holes (9) that are fillable with the matrix material (6) Preferably, the spacer (4) is net-shaped or meshed It can be a net of fibers The bushing (1) can be a fine-graded bushing (1) with equalizing plates (5) within the core As a matrix material (6), a particle-filled resin (6) can be used

Breakdown of transformer oil

Abstract: Some of the factors affecting the dielectric strength of transformer oil are investigated. These factors include the stabilization phenomenon, oil and electrode pretreatment, the effect of oil velocity, the effect of a capacitance parallel to the test cell, and the effects of electrode area and gap spacing. The experimental apparatus and procedure are described, and the results are presented for each of the above factors. Suggestions for future research are offered. >

Pressure sensor with fibre-integrated bragg grating, comprising an integrated temperature sensor with fibre-integrated bragg grating

Abstract: The invention relates to a wavelength-coded pressure sensor (1) with fibre-integrated Bragg grating, which is especially suitable for use at high pressures and temperatures in oil wells. The sensor principle provided for in the invention is based on the fact that the hydrostatic pressure of a liquid or gaseous medium (11) is converted by means of a transducer (1) into a longitudinal lengthening or compression of the fibre. The transducer (1) comprises a measurement or pressure cylinder (7a) which exchanges pressure with the medium (11), and a reference cylinder (7b) which is shielded from the medium (11) or subjected to a counter pressure. Temperature-compensated transducers (1) with a temperature-independent Bragg wavelength μB can be obtained because a suitable temperature-dependence of the mechanical prestressing of the pressure sensor fibre (3) is achieved through the selection of the materials, lengths and arrangements of the fibre holder support (5a, 5b). A fibre-integrated Bragg grating temperature sensor (19, 20) can also be provided. The invention further relates to transducers (1) with different cylinder arrangements (7a, 7b) and a wavelength multiplex configuration comprising several transducers (1).