Recent studies involving large errors in static electricity meters when exposed to step changes in the current waveform are reviewed. Triggered by these findings, a joint European research project has recently started to further evaluate these effects. A description is given of this pre-normative research programme which aims to provide evidence and techniques to resolve this unsatisfactory meter error situation. The need or otherwise for a regulatory and standardisation response to these large meter errors is discussed.

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In an applied research project on the development of a pulsed microwave sulfur lamp prototype of 1 kW, we have discovered an amazing phenomenon in which the plasma forms a ball staying at the center of the bulb despite gravity, thus protecting the glass from melting. In this paper, it is shown that this results from an acoustic resonance in a spherical mode. Measurements of the plasma response to short pulses are presented showing beats at the spherical resonance. It is demonstrated that the beats could result from the simultaneous excitation of two normal modes with a frequency difference of approximately 1%. One of the two frequencies matches precisely the microwave pulses repetition, a little below 30 kHz. Thus this one is due to a forced oscillation, whereas the other one is due to a free oscillation. The phase velocity of sound was calculated as a function of temperature in order to find the series of temperatures at which a resonance would occur if the bulb were an isothermal solid sphere. The mean temperature inside the actual bulb was determined from the only doublet of this series, that has characteristic frequencies close enough to cause the observed beats. In addition, one of these two modes has a spherical symmetry that can explain the plasma ball formation. The obtained mean temperature is consistent with the direct measurements on the bulb surface as well as with the temperature in the core of a similar plasma found in the literature. We have also proposed a model of the resonance onset based on the acoustic dispersion and the sound amplification due to electromagnetic coupling. Key words. molecular plasma-pulsed microwave plasma-plasma confinement-acoustic resonanceacoustic dispersion-sound amplification due to electromagnetic coupling-plasma of sulfur-electrodeless light bulb-high-pressure lamps-light sources

In recent years, low-voltage DC (LVDC) grids allow for a more efficient and sustainable integration of renewable energy sources. In order to facilitate such transition, though, several normative and metrological aspects need to be addressed. In particular, the calibration and type-testing of DC power and energy meters shall rely on traceable reference systems, capable of assessing the meters' performance in nominal and distorted conditions. This represents a preliminary yet crucial step towards the actual deployment of LVDC grids in modern power systems. In this paper, we present the design of a DC power reference system and discuss the main implementation challenges. In this regard, we identify the most significant uncertainty sources and propose ad hoc measurement procedures and hardware solutions to minimize their contributions.

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