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The growing use of renewable energy sources and sustainable technologies has increased the attractiveness of low-voltage DC distribution grids. Despite initial research and standardization work, the definition of power quality (PQ) issues and their related compatibility levels in DC grids and the related measurement techniques remain in their infancy. The lack of available measurement results obtained in real-world situations is a major shortcoming. In this paper, the results of a measurement campaign obtained in a configurable bipolar 350 V/700 V DC microgrid in an urban environment are presented. Voltage and current signals were registered continuously at different positions in the microgrid with a sampling rate of 500 kSa/s while changing the configuration of the microgrid; the resulting data were analyzed afterwards, with a focus on DC voltage and current variation, ripple, and spectral analysis. The measurements were taken with custom-designed metrology-sound measurement equipment. The measurement results provide input to the development of DC PQ analysis tools and the standardization of DC PQ measurement methods. Furthermore, the experience obtained will be beneficial for utility companies and regulatory authorities for reliable planning-level and compatibility-level surveys. [ABSTRACT FROM AUTHOR]

In 2015, the energy measurement of some static electricity meters was found to be sensitive to specific conducted electromagnetic disturbances with very fast current changes caused by highly nonlinear loads, leading to meter errors up to several hundred percent. This article describes new results on the electromagnetic compatibility (EMC) of 16 different meters from all over Europe when exposed to real-world disturbance signals. Those test signals were obtained from household appliances and onsite measurements at metered supply points all over Europe. The results show that also the interference signals recorded onsite can cause measurement errors as large as several hundred percent, even for meters that pass the present EMC standards. This unambiguously demonstrates that the present immunity testing standards do not cover the most disturbing conducted interference occurring in present daily-life situations due to the increased use of nonlinear electronics. Furthermore, to enable the adoption of potential new test waveforms in future standards for electricity meter testing, artificial test waveforms were constructed based on real-world waveforms using a piece-wise linear model. These artificial test waveforms were demonstrated to cause meter errors similar to those caused by the original real-life waveforms they are representing, showing that they are suitable candidates for use in improved standardization of electricity meter testing. [ABSTRACT FROM AUTHOR]

A sampling current ratio measurement system has been developed to calibrate the voltage dependence of ratio error and phase displacement of current transformers (CTs) used for medium-voltage (MV) and high-voltage (HV) applications. The influence of voltage-induced leakage current on the apparent ratio error and phase displacement of the reference circuit was unambiguously demonstrated using a novel measurement method. Measurement results for voltages up to 24 kV show that the observed leakage current is purely capacitive and caused by the shielded cable capacitance of the HV cable used to feed the current. The maximum ratio error and phase displacement were found to be about 100 parts in 106 and $100~\mu $ rad for the smallest current of 100 A used for these investigations. Since these values scale linearly with the applied voltage and inversely proportional with current, the assumption of negligible voltage dependence used in other reference systems presented in literature is questionable. Using the corrected reference circuit, a commercial class 0.2S MV CT with 2500-A nominal current was calibrated at voltage levels up to 24 kV. The voltage dependence of ratio error and phase displacement for primary currents up to 500 A was demonstrated to be capacitive as well, with a maximum impact on the current ratio of almost 0.9% for a primary current of 100 A (corresponding to 3.6% at 1% of nominal current). This value is beyond the limits of in-force standards, which emphasizes the necessity of implementing voltage dependence testing in those standards. [ABSTRACT FROM AUTHOR]

To assess the reliability of dc energy measurement equipment on-board trains, a setup was developed to characterize current transducers under realistic operating conditions. The operating principle is based on a current ratio measurement technique. The reference sensor is a high-precision zero-flux current transducer in combination with a broadband high-precision current shunt. The influence of ac distortion on this reference sensor was found to be within a few parts in 106 using an initial version of the setup, in which ac distortion was applied through a separate winding. A revised version of the setup employs a programmable electronic load to apply dynamic currents up to 600 A. The setup was used to characterize a 100 $\mu \Omega $ high-current shunt resistor. The effect of dissipative heating on the dc transresistance error was around 0.03 %, with a settling time of about half an hour. The short-term intrinsic current dependence was also around 0.03 %. The effect of ac distortion was within a few parts in 106. The intrinsic current dependence and the onset of the heating effect were also observed when exposing the sensor to a dynamic current profile that was recorded during a trip between two successive underground train stations on Metro de Madrid. These results demonstrate that the setup described in this paper is very effective for characterizing dc current sensors for practical railway applications. Future work will concentrate on even more demanding current signals, such as chopped signals, and on other types of sensors and measurement systems. [ABSTRACT FROM AUTHOR]

An optoelectronic pulse drive system based on commercially available telecoms optoelectronic components and a field-programmable gate array has been developed. In order to allow the use of ac-coupled optoelectronic components, a method of adding and subtracting complementary pulses was developed. The system was used to drive a Josephson junction array to synthesize quantum-accurate voltage waveforms. These waveforms will be used in voltage waveform metrology applications. Results from the synthesis of sinusoidal unipolar voltage waveforms from 3 to 300 kHz are presented. The margin of operation was measured and shown to require an optical pulse height stability better than 0.15 mW. The use of delta–sigma code with repeated sections, suitable for a quantum voltage digitizer was also examined. A test code corresponding to a delta–sigma feedback loop rate of 250 MHz was used to synthesize a 3.125 kHz sinusoidal waveform. [ABSTRACT FROM AUTHOR]

AC–DC measurements have been performed on a commercial thermal transfer standard (TTS) using a pulse-driven ac Josephson voltage standard with a small cryostat enabling shorter voltage leads. A 20 mV RMS output voltage was chosen, close to the maximum value that can be obtained without lowfrequency compensation (at a sigma-delta code amplitude of about 10 %) and close to the upper limit of the TTS in its 22 mV range. The measured deviation at higher frequencies, which is due to the length of the voltage leads, was an order of magnitude smaller than was observed before with a normal cryostat. The observed square dependence on the signal frequency and cable length follows exactly the expected behavior. All results agree well with the calibrations performed using a micropot reference system. Furthermore, the influence of other cables and equipment was investigated. The measurement results can be quantitatively understood both in terms of a lumped circuit description and in terms of reflected waves. [ABSTRACT FROM AUTHOR]

A sampling current ratio measurement system has been developed, tested, and validated for the accurate complex ratio measurement of ac current transducers. Calibrations can be performed for primary currents up to 10 kA with typical expanded uncertainties of 5\cdot 10^\mathrm \mathbf -6 in magnitude and 5 $\mu $ rad in phase ( $k=2$ ). A unique property of the system is the use of digitizers for sampling of the secondary current signals and step-down transformers with a large number of current ratios. Therefore, the system does not require the current transducer under test to be a current transformer having a nominal ratio equal to the reference current transformer. Furthermore, it allows for the accurate calibration of a large variety of different current transformers and other types of current transducers. A bilateral comparison between VSL and NRC confirms the stated uncertainty. [ABSTRACT FROM PUBLISHER]

A measurement setup is developed for the accurate ratio measurement of ac current transformers (CTs) for primary currents up to 5 kA. A unique property of the system is the use of high-quality digitizers for sampling of the secondary current signals and step-down transformers with different current ratios. This allows for accurate comparison of CTs even when their nominal ratios are not equal. The calibration results of the key components in the setup show that the sampling current ratio bridge has a ratio uncertainty of better than 2 \muA/A in magnitude and 0.8 \murad in phase for CT-under-test current ratios that do not differ by more than a factor of 5 from one of the ratios in the reference CT. The linearity of the bridge for input currents changing between 1% and 120% of nominal input current is better than 4 \muA/A in magnitude and 0.5 \murad in phase. [ABSTRACT FROM PUBLISHER]

This paper describes a power measurement setup that is able to measure power up to the MHz region. The setup consists of a commercial digitizer together with a switch unit, and buffer amplifiers to alternately measure the voltage and current channel. A reference AC voltmeter provides an absolute reference by simultaneous measurement of the rms voltage of one channel, which significantly reduces the need for flat frequency response of the setup. The method described in this paper makes complex voltage ratio measurements possible in the range of 50 Hz up to 1 MHz with an uncertainty of a few parts in 10^6 and in addition can be applied in wideband power measurements. Using our new method, the frequency response of cables and several other components is no longer a limiting factor for power measurements up to 1 MHz. [ABSTRACT FROM PUBLISHER]

A Josephson arbitrary waveform synthesizer (JAWS) has been developed in order to generate quantum-based ac voltage signals. The key component of this JAWS is a modified commercial 30-Gb/s pattern generator that can generate ternary patterns (containing the values +1, 0, and -1, resulting in bipolar pulses). The new pulse-drive electronics have been successfully tested by driving Josephson arrays with bipolar current pulses from 1 to 30 Gb/s in order to study their current-voltage characteristics and the spectra of the JAWS signals. [ABSTRACT FROM AUTHOR]

The European Josephson arbitrary waveform synthesizer (JAWS) project addresses the Jack of instrumentation and knowledge for accurate and traceable measurement and generation of alternating (AC) voltage with arbitrary waveforms. The objective is to develop a standard based on a JAWS, a precise instrument that links the generated voltage to the Josephson effect, which in turn: relates voltage to fundamental constants and frequency. The standard alms at synthesized voltages up to 10 mV, frequencies up to 10 kHz and uncertainty smaller than 100 μV/V as a first step. This paper reports on the progress in developing the key components for JAWS. [ABSTRACT FROM AUTHOR]

A high accuracy current source has been developed for the generation of very small currents (below 200 pA) based on applying a linear voltage ramp to a capacitor. Using software-controlled compensation for the nonlinearity of the voltage ramp, a stable current can be reached within a few seconds. A voltage ramp within typically 10.10-6 of any desired value between less than 1 mV/s and several hundreds of mV/s can be realized. Using a high quality air-dielectric capacitor, currents below 200 pA can be generated With an uncertainty of 20 μA/A (k = 2), with a lower limit 0f 2.0 aA (k=2). [ABSTRACT FROM AUTHOR]

Presents a study that exploited two complementary single electron tunneling devices for use in electrical current metrology. Set current source; Current steps for the R-pump with smaller junctions for different frequencies and series resistances; Summary and conclusion.

Presents a study that analyzed different measurements setups for a programmable Josephson voltage standard. Arrays and measurement setups; Results of the study; Conclusion.

The energy efficiency of transportation is a crucial point for the rail and metro system today. The optimized recovery of the energy provided by the electrical braking can lead to savings of about 10% to 30%. Such figures can be reached by infrastructure measures which allow the recovery of the breaking energy that is not directly consumed by the rail system and dissipated in rheostat resistors. A methodology for the accurate estimate of such energy is valuable for a reliable evaluation of the cost–benefit ratio associated with the infrastructural investment. The energy can be estimated by measuring a braking current flowing in the rheostats. The varying duty-cycle associated with the high dynamic variation, from zero to thousands of amperes, makes the current measurement very challenging. Moreover, the digitization of such waveforms introduces systematic errors that affect the energy estimation. To overcome these issues, this paper proposes a technique to measure the power and energy dissipated by the rheostat of a DC operated train with high accuracy. By means of an accurate model of the electrical braking circuit (chopper and rheostat) and the frequency characterization of the current transducer, a correction coefficient as a function of the duty-cycle is estimated. The method is then applied to data recorded during a measurement campaign performed on-board a 1.5 kV train of Metro de Madrid during normal operation. Using the proposed technique, the estimation of the dissipated braking energy is improved by 20%. [ABSTRACT FROM AUTHOR]