Harald Schwarz

3D Finite Element analysis of magnetic shunts and aluminum shields in clamping frames of distribution transformers

This paper presents a 3D Finite Element (FE) analysis of stray losses in core-type distribution transformers, where a magnetic shunt and a C-shape electromagnetic shield are utilized to protect a clamping frame of stray fluxes produced by high current leads (HCLs) of low voltage bushings. A real clamping frame of a three-phase core-type oil distribution transformer is utilized to study the electromagnetic behaviour of the shields and magnetic shunts. The electrical steel of the magnetic shunt is modelled utilizing anisotropic properties and aluminum is employed for the electromagnetic shield. Impedance boundaries were utilized in the frame and in the aluminum shield to compute the stray losses. Stray losses in the clamping frame are computed for three cases: 1) frame without any shielding method, 2) frame with a magnetic shunt, and 3) frame with a C-shape aluminum shield. The current in the HCLs were varied from 2 kA to 20 kA. The results obtained between the use of electromagnetic shield and magnetic shunts in frames of distribution transformers are also discussed in this paper.

Urban photovoltaic potential

Due to the progress in the field of solar cells the widespread use of photovoltaic systems in the urban areas appears to have a significant breakthrough. The energy supply will be challenged with high urban photovoltaic consumers. It has to be investigated, whether the existing network structures are able to integrate the large-scale photovoltaic power.

Harmonic impact of decentralized photovoltaic systems and limitation of photovoltaic capacity in low voltage grid

Photovoltaic energy has grown massively in Germany in recent years, so that the government plans to rein in the boom by cutting generous subsidiaries. Still, a larger number of photovoltaic systems will be integrated into the energy supply networks, which are mostly connected to the low voltage grid. This paper aims at finding out the impact of urban decentralized photovoltaic systems on the power quality including harmonics, voltage change and load digestion.

Potentials of microgrids - RES infeed, stationary storage and controllable loads modelling

The general possibility of combining electric vehicles, PV systems and storage devices is useful for the reliability and quality of electricity distribution. It contributes to optimal operation of distribution networks and minimization of transmission losses. The potential of a microgrid concept can be evaluated using a reliable and reality oriented simulation allowing various case studies and resizing of microgrid elements. This paper presents an attempt to develop and simulate and robust system based on long time collection of real data.

A new EMS facility for the test of large widespread systems

A new EMC susceptibility test method for a huge system, like a complete train, is described. The continuous wave (CW) and transient environment of a train are simulated with a repeating electromagnetic nanosecond pulse, which is fed onto a modular construction to realise an infinite enlargement of the test-facility. The produced test field, that fulfils the requirements of an anechoic chamber, is applied only a few seconds and qualifies the method as an economical one.

The influence of vehicle hull on a radiated emission

This paper contributes to an issue related to prediction of potential electromagnetic compatibility problems in a vehicle design process. This work begins a series of articles describing the method of assessment and prediction of electromagnetic radiation of complex, large scale, electrical objects, such as electric cars. This paper examines the influence of a vehicle hulls on an electromagnetic radiation excited by an electrical device located inside it. For this purpose, a simplified model of vehicle electronics is taken. A set of electronic devices and their enclosures can be considered as an unintentional source of electromagnetic field. The impact of hull is analyzed from this point of view. The statistic estimation gives an account of how the hull changes the field strength, and what is the new direction of the main field pattern lobe. Typical resonant frequencies of the hull and Q-factor are considered, as well as various positions inside the car where the electronics can cause potential electromagnetic compatibility problems. Although the estimation is not absolutely precise, the simplified model gives a comprehensive assessment of the electronics emission. The goal is to find out whether the car hull and electronics inside can be still considered as an unintentional emitter, to compare the radiation characteristics with the unintentional emitter model and to know limitations of this approach. Results obtained from the analysis are used in a methodology aimed at prediction of the system-level emission on the basis of component-level emission measurements. However, they can be used in making rapid measurement and radiation prediction methods, which are required at a design and vehicle prototyping stage, etc. in software like rule-checking or expert systems.

A DWT-based endpoint detector for transient signals

This paper addresses the problem of accurately locating the endpoints of transient signals in the presence of background noise. Transient detection is accomplished by means of wavelet thresholding using an appropriate analysis filter bank. The suitable choice of the system parameters - which depends on the used measuring system and the frequency content of the transient signals - is discussed.