Metrology for high voltage direct current (Delivered 2013) ENG07
The research supports a wide implementation of HVDC transmission in Europe. The research addressed metrological challenges that support a reduction of losses in HVDC transmission, eases the introduction of renewable energy sources, enhances the stability of electric power grids, supports low loss long distance energy transmission and ensures fair trade between organisations employing the grid. The main areas of research were Loss evaluation, Power quality and Metering. Read more
The project was coordinated by PhD Anders Bergman at RISE. One of the main outcomes was 1000 kV DC calibration systems maintained at RISE.
Metrology for the electric power industry 14IND08
The project will produce the following results:
- New reference standards and linearity extension methods to prove the accuracy of measurement of lightning impulse test voltages also in the ultra-high voltage regime.
- New calibration references and calibration methods both for very fast voltage transients up to 500 kV and 200 ns rise-time, and for surge current in the kA range and rise-time down to 10 ns.
- Methods and equipment for measurement of losses of power transformers, reactors, capacitors, and power cables at the very low power factors typical for the applications.
- Methods for loss measurement of HVDC converter stations as the difference between input and output power. Part of this will be realisation of a non-invasive, high-precision, current transformer reference.
New, non-conventional technologies are being more and more widely applied e g optical Faraday effect based sensors, hybrid electrical/optical sensors and air core Rogowski coils for current measurement; and voltage dividers or optical Pockels effect based systems for voltage measurement or upgrading of conventional instrument transformers with digital or optical readouts.
These solutions are potential replacements for traditional instrument transformers for power frequency measurement on medium and high voltage power lines, and they show great promise in enabling lightweight, accurate measurement systems for voltage and current, both for fundamental and harmonic frequencies. However, at present they lack the level of accuracy needed for metrological applications.
The aim of the project is to support wider application of novel sensor technologies in future power networks. In order to complement the emergence of the new technologies, the most promising of them have been selected. Read more …
Nationally funded research
Evaluations of a High power, Medium frequency and High voltage transformer prototypes as main part of a Solid State Transformer
It is in many DC-DC power applications desirable – and possible - to minimize size and weight of transformers by increased operation frequency. The technology is young, especially for high power, and many parameters are not well known.
A project has therefore been formulated, in continuation of cooperation between RISE and Chalmers, and financed in common by RISE WMSG platform, Chalmers and ÅForsk foundation. The goal is to evaluate the electrical characteristics of two prototype medium-frequency high-voltage power transformers that were designed as part of a Licentiate thesis at Chalmers.
Working prototypes were built as part of a Master thesis in cooperation with RISE. The project will examine and bring forward the design and manufacturing processes and methodologies necessary to design and build such transformers. The evaluations will comprise both theoretical as well as experimental work. The project is vital and will provide the insights needed for future work to develop an updated version of the transformer.
Development of a high current transformer ratio standard
Accurate measurement high current relies on an accurate transformation of the high current into a low current, typically in the range 1 to 5 A, that can be measured by instruments. Calibration of such current transformers needs access to verifiable references. The research aims at development of methods and technologies to build a mobile 10 kA current reference standard with world-class accuracy at power frequencies.
The project also includes establishment of unbroken traceability chains from 5 A to 10 kA. The main goal is both to extend our in-house capabilities as well as to offer high-current calibration services on-site at our customer’s premises.
Qualification of a modular 1000 kV voltage divider as reference for AC and Switching Impulse voltage
The HVDC project (link needed) led to realisation of a modular divider for 1000 kV DC voltage with outstanding characteristics. The concept is furthermore well suited for on-site work at the premises of the user.
An effort is being made to extend the usefulness of the divider by characterisation of its performance for AC and switching impulse up to a peak voltage of 1000 kV. The goal for performance at AC is to provide a secondary mobile reference standard useful at voltages above 250 kVrms available with our systems based on very accurate compressed gas capacitors.
The goal for switching impulse is to develop a new primary reference up to 1000 kV peak with an accuracy of at least 0.5 %
Amelioration of best calibration uncertainty for DC
In the HVDC project the two 1000 kV voltage dividers owned by RISE could be proven to permit 1000 kV calibrations with a best uncertainty of 0.005 %. Further work has been done and has led to a reduction to 0.002 %.