This paper describes the setup of a traceable calibration system for conventional or non-conventional current sensors even with digital output. The system is lately developed at PTB within the frame of the European project “FUTUREGRID II”. Details of the system components are presented. The absolute phase errors of the two-channel generator related to the pulse per second time reference of the global positioning system can be configured to almost zero. The accuracies of the reference current transformers are within ±10 μA/A and μrad at power frequency. The sampled value receiver box is firstly validated for the sample rate of 4 kHz according to the IEC standard 61869-9 [1].

Sampling-based calibration systems for calibrating “Sampled Value” (SV)-based instruments for substation automation require synchronised and time-aligned sampling processes. As the signal frequency of the power grid is always asynchronous to the standardised sampling frequencies according to IEC 61869-9, the sampled waveforms of the calibration system and of the SV-based device under test can be resampled to be synchronised and to allow better accuracy in the following measurements based on the Discrete Fourier Transform (DFT) of the resampled waveforms. The paper presents simulations and results for different resampling algorithms. A modified sinc interpolation method with a finite impulse response (FIR) is presented. The deviation of the results for the root mean square (RMS) and phase angle is in the order of 10−8 V/V (or rad) for normalised frequencies of up to 20% of the sampling frequency. No practical degradation in the presence of noise and harmonics could be observed. In addition, laboratory experiments demonstrate the realization of the proposed resampling process in the future SV-based calibration systems for SV-based instrumentation.

The work progress on a new current transformer test set at PTB is described. The operation range for the ratio based bridge is intended for frequencies from 16.7 Hz up to 20 kHz. Equal setups of magnetically shielded current comparators with primary windings for currents from 100 mA up to 5 A convert the secondary currents of the standard current transformer and of the transformer under test (DUT) into proportional voltages. The errors of the DUT are calculated from the subsequent measurement of the complex voltage ratio. At 50 Hz, the measuring system offers a basic accuracy in the order of less than ± 2 ppm or μrad respectively.

This paper describes a simple and easy to implement algorithm for synchronizing analog-to-digital converters to the fundamental of a continuous periodic signal. It is based on the discrete-Fourier transform (DFT) on sampled data and uses DFT- leakage detection to ensure a synchronous sampling. It may be applied to distorted waveforms in general, irrespective of the type of ADC used, and no windowing functions on sampled data need to be applied.

This paper reports the incorporation of a Josephson waveform synthesizer (JWS) into the primary standard for AC electrical power at the Physikalisch-Technische Bundesanstalt (PTB). The increase to 10 V of the amplitude delivered by the JWS has allowed matching of the levels of the signals measured to determine the active, reactive, and apparent power-at the 120-V and 5-A level, which is also measured by the device under test. The inherent noise- and drift-free voltages delivered by the JWS allow calibration of the core sampling voltmeter of the PTB primary power standard with an uncertainty of 0.4 muV/V(k = 1) in 100 signal periods and as part of the measuring sequence.