Resonance Behaviour of Shielded High-Voltage Laboratories and the Effect of Interference on Impulse Measurements

Abstract

As the national metrology institute of Germany, the Physikalisch-Technische Bundesanstalt (PTB) is dedicated to ensure the quality of metrology in Germany by performing its tasks. The working group 2.32 for High-voltage metrology developed a transient recorder with a corresponding software. In the Process of testing the new measuring system there were superimposed oscillations observed. In this paper we want to investigate these observations. Moreover, the influence of the oscillations on the analysis of the measurement data is not investigated so far. The recorded curves in the laboratory are analysed according to de IEC 60060-1:2010 in which context the measurement data is treated by software-based filters and algorithms that perform a nonlinear regression. If the input data is biased too much by interference it can be possible that the measurement and the resulting values are negatively affected. The impulse generator with its spark gaps is assumed to be the source of a high energetic transient electric field. Like many other laboratories the PTB’s high-voltage laboratory is fully shielded with copper foil on the inside of every wall, the floor and the ceiling. The architecture of this laboratory room forms an almost perfectly rectangular box-shaped cavity with electric conductive walls. This formation is capable of behaving like a hollow waveguide conductor for certain frequencies. Thus, it is possible that the resonance frequency of the laboratory room is excited by the impulse generator.