17IND06 FutureGrid II: Metrology for the next-generation digital substation instrumentation

• Forschungsstelle: METAS
• Projektnummer: F-5212.30098

Schlüsselwörter (Englisch)

Electrical power grid, real-time, digital sensor technology, next generation instrumentation, digital substation, secure time synchronisation, stand-alone merging units

Kurzbeschreibung (Englisch)

Decentralisation of the energy generation due to renewable sources causes an unprecedented shift of the power flow away from the traditional top-to-bottom model, entailing greatly increased reliance on distributed measurements and real-time control. Thus, the future electrical power grid requires next generation instrumentation for substations to ensure stability and security. This project aims to develop the metrological infrastructure for digital sensor technology, their digital data processing, to apply new, precise and secured time synchronisation and to prove product quality, creating a large demand for new devices benefitting instrument manufacturers, increasing their competitiveness and maintaining their leading position worldwide.

This is a joint research project carried out in the framework of the European Metrology Programme for Innovation and Research (EMPIR) (see:http://www.euramet.org/research-innovation/empir/). The EMPIR initiative is co-funded by the European Unions's Horizon 2020 research and innovation programme and the participating states. METAS is one of the project partners in the project.

Projektziele (Englisch)

The specific objectives of the research are:

1. To establish calibration methods to support dynamic testing of digital instrument transformers (IT) for rated voltages up to 400/√3 kV and at least 2 kA. In addition, to support technology integration into digital substations, including real-time monitoring systems associated with power quality (PQ) and synchrophasor measurements with uncertainties from 30 ppm under laboratory conditions and up to 0.1 % under on site conditions.
2. To develop reference standards for the calibration of instruments with digital input or output, in order to support the transition to digital substations. This includes studies on increasing sampling rates beyond those specified in IEC standards, and on the accuracy of distributed digital power measurements.
3. To develop metrological tools for the characterisation of devices that exploit sampled values in digital substations, such as all-digital power and power quality meters and phasor measurement units (PMUs). This includes e.g. studies on limitations due to latency and computation time, and characterisation of error sources in order to provide proposals for an enhanced protocol for sampled values.
4. To develop traceable reference standards for the verification of time and synchronisation methods. This includes study on techniques and algorithms such as PTP and White Rabbit for the synchronisation of sampling to a common time reference, both within and between digital substations. In addition, to carry out studies on secure protocols for time dissemination. To develop and validate satellite-independent PMU utilising distributed sensors.
5. To facilitate the take up of the technology and measurement infrastructure developed in the project. Target stakeholders include the measurement supply chain (instrument manufacturers), standards developing organisations (IEC TC38 WG 55, IEC TC57 WG 10, IEEE TC39, IEEE P1588) and end users (energy distribution companies).

METAS contributes to objectives 3, 4 and 5.

Abstract (Englisch)

• A3.1.1 (software): A user-friendly software platform able to read and transmit sampled values (SV) together with the corresponding analog signal version has been realized at METAS. Several tests with commercially available instruments (e.g. EFOCT from Condis and the digital bridge WM3000I from Zera) allowed to successfully validate the platform developed in the framework of this activity.
• A3.1.3 (Hardware): Studies of the effects that different resolutions, noise, time-stamping and the deploying of different analog-to-digital converters (ADC) have on digital power values have been performed for two different ADC types, a SAR- and a Delta-Sigma-type. These ADCs have been tested with tree different configurations with the same sampling clock and with different sampling clocks.
• A3.1.4 (Metering): Using the platform of A3.1.1, the impact of the harmonics and of the power frequency fluctuations on the metering related quantities has been studied.
• A3.1.5 (Metering): A test system for the comparison of the traditional and SV metering quantities has been developed.
• A3.1.5 (Summary report): The features and test results of all the activities of the first part of the package have been reported in a Summary. This summary has not been delivered by the lead partner of this activity (TUBITAK) yet.
• A3.2.1 (Grid control): Effects of resolution, noise and time stamping on estimation of the relevant parameters using the identified algorithms to implement in a digital PMU prototype have been studied.
• A3.2.2 (Grid control): A software-based real-time demonstrator of a PMU with SV input has been developed.
• A3.2.3 (Grid control): a PMU with SV input prototype has been set up and the parameter extraction as well as the real-time functionality has been analyzed (see below)
• A3.2.5 (Validation Report): METAS is summarizing in these days the activities and results about the digital PMU work performed by the WP3 partners. Up to now no information from partners has been received.
• A3.2.6: (publication): METAS has published a conference paper (AMPS 2021) about the digital PMU work, with title:"Phasor Measurement Unit and Sampled Values: Measurement and Implementation Challenges".

Umsetzung und Anwendungen (Englisch)

The participation of METAS to the project Future Grid II allowed to set up a complete calibration system able to characterize phases and amplitudes of signals (analog and digital) produced by devices working in accordance with the communication protocol IEC 61850-9-2. Two articles [1], [2] have been written describing the METAS SV calibration system. The SV publisher functionality of this test bench makes possible to characterize instruments with SV as input, like for instance the ZERA WM3000I/U, which are non-conventional current/voltage transformer measuring bridges. In this context, a calibration service for these particular devices has been set up at METAS (currently in Lab 5213) and some characterizations for customers have already been performed during the year 2021. A paper describing the challenges of calibration for such instruments has been published [3]. A version of the METAS SV calibrator to employ in the electrical substation is currently under development in the framework of the Innosuisse project (2019-2022) with Condis SA as industrial partner.

The activities about the development of PMUs with digital input allowed METAS to build a stand-alone prototype of such an instrument, which works in real-time exclusively with SV as input data. About this work, we have written a conference paper for AMPS 2021 [4], which has been accepted and now we are planning to write the extended version.

New tests aimed to characterize the response of the Non-Conventional Instrument Transformers (NCITs), whose output is formatted as SV, in dynamic and distorted condition as described in the IEC Std 60255-118-1 has been recently performed at METAS. To this end we have used the Electronic Fiber Optic Current Sensor (EFOCT) loaned to us by Condis for the Innosuisse project. A conference paper, which describes the analysis of the performed tests is currently being finalized and will be submitted for SGSMA 2022 conference

Publikationen / Ergebnisse (Englisch)

[1]        M. Agustoni and G. Frigo, “Characterization of DAC phase offset in IEC 61850-9-2 calibration systems” IEEE Transactions on Instrumentation and Measurement, pp. 1–1, 2021.

[2]        M. Agustoni and G. Frigo, “Characterization of a non-real time sampled values publisher calibrator” à submitted to TIM.

[3]        Frigo, Guglielmo, and Marco Agustoni. 2021. "Calibration of a Digital Current Transformer Measuring Bridge: Metrological Challenges and Uncertainty Contributions" Metrology 1, no. 2: 93-106. https://doi.org/10.3390/metrology1020007

[4]        G. Frigo and M. Agustoni, “Phasor measurement unit and sampled values: Measurement and implementation challenges,” in 2021 IEEE 11thInternational Workshop on Applied Measurements for Power Systems (AMPS) (AMPS 2021), Cagliari, Italy, Sep. 2021

[5]        G. Frigo and M. Agustoni, “Characterization of a Non-Conventional Instrument Transformers in Low-Inertia Power Systems"  to submit for SGSMA 2022.