Dirk Peier

Thermal and Electrical Properties of Aluminum Nitride Filled Epoxy-resin Compound

Epoxy resin compounds are manufactured with silica glass and aluminum nitride as filling material at various filling ratios. The thermal conductivity and electrical properties, like dielectric loss or electric strength, are measured and compared as regards to an utilization as electrical insulator.

Absolute Determination of High DC Voltages by Means of Frequency Measurement

A novel absolute measuring procedure is presented for the definition of fixed points of the voltage in the 100 kV range. The method is based on transit time measurements with accelerated electrons. By utilizing the selective interaction of a monoenergetic electron beam with the electromagnetic field of a special cavity resonator, the voltage is referred to fundamental constants and the base unit second. Possible balance voltages are indicated by a current detector. Experimental investigations are carried out with resonators in the normal conducting range. With a copper resonator operating at the temperature of boiling nitrogen (77 K), the relative uncertainty of the voltage points is estimated to be ± 4 × 10-4. The technically realizable uncertainty can be reduced to ± 1 × 10-5 by the proposed application of a superconducting niobium resonator. Thus this measuring device becomes suitable as a primary standard for the high-voltage range.

Fiber optical online monitoring for high-voltage transformers

The increasing significance of a current state dependent maintenance and the demand for a reliability and an economical operation of power industry devices led to a discussion about monitoring and diagnosis possibilities for high-voltage (h-v) transformers which are one of the most important valuable network components. In the area of high field devices only the use of optical measurement techniques offers the possibility to supervise the characteristic measurands, e.g. critical temperatures or the occurance of Partial Discharges (PDs). Therefore a temperature detector based on Fiber Bragg Gratings (FBG) is presented, who allows a semi-distributed measurement at the active part of the h-v transformer. In this connection some points dealing with cost-effective signal processing units and details about a succesful integration of the sensing elements are investigated and the experimental results are shown. Partial discharges at transformers mainly occure in the insulating oil and on oil-surfaces. Hereby the quantity and amplitude of the PDs are relevant to the actual assessment of the transformer. To analyze the reason for occurrence of PDs it is necessary to localize and characterize the PD source. For on-line detection of PDs the measuring equipment must be placed into the oil. For this application a potential free experimental setup, based on a fiber optical system, for PD detection is described. By using a Mach-Zehnder-Interferometer for acousto-optic measurement the existence of PDs can be detected. By using fiber optical sensors for temperature and PD detection it is possible to watch the operating conditions of h-v transformers and avoid critical states.

Electric strength and dieletric properties of µm-polymer-films

The electric strength and the dielectric properties of different polymers with film thicknesses from s = 1 … 100 µm are presented. The experimental data of the electric strength of PMMA and an acrylic polyester resin is obtained without partial discharges by the use of a special test item design. Based on these results a model is then presented which may describe the breakdown mechanism in consideration of the molecular properties of the polymer. Therefore the formalism of Townsend mechanism, which is known from the breakdown of gases, is used. The results of this model calculation match the experimental data.

Analytical and numerical computation of the electric field of a hyperboloid-plane geometry with and without space charges

In the important context of dielectric aging and space charges in dielectrics the computation of the local electric field of electrode geometries is of big significance. Therefore, a computation method for the electric field of hyperboloid-plane electrode setups with and without space charges is described in this paper. In absence of space charges the electric field can be calculated analytically. In case of space charges there is no such analytical solution. Therefore, a more general, numerical approach based on the method of the finite differences is proposed. Furthermore, some experimental examinations on this electrode configuration are presented.

Measurements of the Induced Power in a Shape Shifting Transmission Line According to Immunity Tests in Reverberation and Semi Anechoic Chamber

Measurements of the induced power in a shape shifting transmission line are performed in the semi anechoic and reverberation chamber. The test setups are according to immunity tests. The device under test is a bar antenna, seen as transmission line, which is investigated for 3 geometric constellations. The differences between the measurement results in both test environments are pointed out. Finally, a maximum hold, over all measurements in the semi anechoic chamber, is compared to one measurement in the reverberation chamber.

On the conductivity of pure epoxy in time and frequency domain

This paper contains examinations concerning the conducting behavior of pure epoxy resin in time and frequency domain First, time resolved current measurements are presented to analyze the behavior in time domain experimentally. The conducting behavior is recorded in dependence of temperature and applied DC-voltage. Based on the experimental examinations an equivalent circuit diagram is developed which offers the possibility to simulate the measured charging and discharging currents and to perform frequency depending examinations in the range significantly lower 1 Hz.

Electrical mode stirring by reactively loaded antennas in reverberating chambers for EMC

Electrical mode-stirring in reverberating chambers for EMC is accomplished by antennas which are loaded by variable reactances. The principle is derived from a network model of the chamber, which employs measurable coupling factors. The concept is experimentally confirmed in the GHzrange for a chamber with four conical antennas. One antenna is connected to a generator; the other three antennas are reactively loaded by variable short circuit plungers.

Pd measurement system for predicting the long-term behaviour of ignition transformers

High requirements have to be met with regard to the quality of ignition systems due to the integration of power and sensor electronics in ignition transformers and the simultaneous more compact form of construction of Otto engines. This has to be proved by means of short-time tests with the newly-produced systems. Partial discharge diagnosis has been an important measure for quality checks in the field of high voltage engineering since many years. The use of partial discharge diagnosis for the prognosis of the long-term behaviour of ignition transformers with an acceptable amount of technical devices is documented in the following.

Langzeitverhaltens von Zündtransform atoren

Die Integration von Leistungs- und Sensorelektronik in Zundtransformatoren bei der gleichzeitig kompakteren Bauweise moderner Ottomotoren stellt hohe Anforderungen an die Qualitat von Zundsystemen, die durch Kurzzeittests im Neuzustand zu belegen ist. Die Einsetzbarkeit der Teilentladungsdiagnose, die bei energietechnischen Betriebsmitteln seit Jahren fester Bestandteil qualitatssichernder Masnahmen ist, zur Prognose des Langzeitverhaltens von Zundtransformatoren mit vertretbarem apparativen Aufwand, wird im Folgenden dokumentiert.