At the Institute of Power Transmission and High Voltage Technology (IEH) we develop and improve measurement techniques for the measurement of high amplitude impulse voltages and transient electromagnetic fields.

In the last years one main topic in this field has become the detection and measurement of partial discharges. Here we basically deal with modern methods of noise reduction, with acoustic PD measurement techniques and with unconventional UHF partial discharge measurement and localisation techniques.

 

The operation of electric power networks above their initial dimensioning levels and longer than their estimated lifespan requires a detailed monitoring of the operating conditions to ensure a safe supply with electric power also in the future (Life Cycle Management). For this task the diagnostic tools which are necessary for different apparatus are developed or improved (e. g. partial discharge measurement, Frequency Response Analysis, moisture determination, dissolved gas analysis, vibration measurement, on-line monitoring). These tools can be used to predict the overload capacity and residual life time of a H.V. apparatus. On the other side service and maintenance strategies for H.V. equipment are developed (asset management).

Regarding the design of high voltage equipment new materials (e. g. natural and synthetic esters) are investigated concerning their physical, chemical and electric properties. By means of modern software tools, e. g. finite element analysis (FEM) and Computational Fluid Dynamics (CFD), the oil flow distribution and the thermal behaviour of power transformers can be investigated and optimized. The research area Gaseous Dielectrics is characterized by topics like investigation of dielectric properties of pure SF6 and SF6-gas mixtures, the influence of atmospheric conditions on the dielectric strength of technical insulation designs and the investigation of generation and damping of very fast transients in gas-insulated switchgear.

In this research area new methods, concepts and procedures are developed for the analysis, operation and design of the future decentralized power system with large shares of renewable energies (smart grids). Most relevant topics are:

  • Control and operation approaches for distributed generators, storage systems, electrical vehicles and controllable loads
  • Concepts for flexible decentralized power system architectures and approaches for their optimized design
  • Control and operation approaches (incl. state estimation) for decentralized power systems
  • Methods for reduction of complexity in simulation, optimization and operation approaches with regard to interdisciplinary analysis across voltage levels and energy sectors.

For many years the field of “Electromagnetic Compatibility” has been one of the most important activities at IEH. In the beginning of this work we started with the generation and measurement of electromagnetic field impulses with extremely high amplitudes and very short rise times. The aims have been the simulation of NEMP, LEMP and the simulation of circuit breaker operations in GIS.

Recent EMC research works concentrate on the automotive EMC. One topic is the correlation between full vehicle and single component EMC emission measurement procedures. The main aim is to estimate the emission behaviour of a single component in the car which is not yet available in an early state of its development. Another topic deals with EMC of automotive electric power networks. Due to novel high power electric devices, especially in electric vehicles, it is possible that new impulsive disturbances occur on the electric power supply of the vehicle. These impulsive disturbances may cause new disturbing potential which is not covered by the actual EMC susceptibility standards. The goal of this work is to detect and classify these new impulsive disturbances and also to develop new measurement tools for a convenient recording of these sporadic impulses in the automotive power network with as few coupling disturbances as possible.

Last but not least our activities in the potential-free electric and magnetic field measurement have to be mentioned. For several decades some of our colleagues have been very successful in this domain. In the last few years there have been made significant developments and improvements, especially by the use of VCSEL laser diodes with small operating currents and a high bandwidth.

Power electronics are solid-state electronics used in power systems. They are an essential part of the wind energy system, helping to provide active power control. Power electronics even offer wind turbines and wind plants the possibility to provide ancillary services to the grid.

Magnetic vectorpotential of a transversal flux machine. Image: IEW.

The generator of a wind turbine converts the mechanical energy at the shaft into electrical energy that can be fed into the power grid. The calculation and modeling of this core component is therefore indispensable for the overall design of the drive train and of the entire wind turbine.

Current questions in the field of wind power with respect to the drive train refer to general drive concepts such as the connection of the generator via a reduction gearbox or without a gearbox as a direct drive. This includes different generator concepts and generator types, such as the doubly-fed induction machine, the electrically excited synchronous machine and the permanent magnetic excited synchronous machine, which each have advantages and disadvantages in the respective drive concepts.

The Institute for Electrical Energy Conversion (IEW) is engaged in the field of modeling, design and control of electrical drives. In addition to calculations using the Finite Element Method (FEM), analytical models are further developed and refined in order to provide efficient computation tools with different detail resolution from component to system view. 

Magnetic flux density of a transversal flux machine. Figure: IEW

The IEW provides in-depth component knowledge in the area of calculation, design, manufacturing and control of electrical drives, as well as system knowledge about the associated power electronics and about the boundary conditions required in the application as a generator for grid feed such as sinusoidal feed with low distortion factor, frequency stability and controllable active- and reactive power output

Block diagram for the force calculation of an electrical machine with field-oriented control. Image: IEW

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