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rapporti - Deliverable

Sistemi di misura di riferimento di tensione e corrente per applicazioni in laboratorio e in sito

rapporti - Deliverable

Sistemi di misura di riferimento di tensione e corrente per applicazioni in laboratorio e in sito

L’evoluzione del sistema elettrico e delle tecnologie utilizzate impone l’adozione diarchitetture innovative per la caratterizzazione metrologica dei trasformatori di misura. Sono in particolare proposti e analizzati sistemi di misura di riferimento per la taratura di trasformatori low power, di trasformatori di tensione induttivi in presenza di armoniche. Sono inoltre presentate le modifiche e i sistemi di emergenza implementati sull’apparecchiatura LiOnHV.

In High Voltage measurement field, the need is more and more felt of technical solutions suitable to handle some issues about:
• the on-site calibration of current transformers (CTs) and voltage transformers (VTs), with particular reference to those used in energy measuring equipment;
• the metrological characterization of innovative classes of instrument transformers, so called “nonconventional”, “electronic” or “low power”: such equipment should be more and more commonly used with the spread of communication protocols based on IEC 61850 and of smart grids e supergrids;
• the evolution of power quality measurements in high voltage, with particular reference to the impact and the influence of instrument transformers within the measuring equipment. In order to pursue these goals, on the basis of the experience gained with on-site tests, some components of the equipment for the verification on-site of the accuracy of instrument transformers, which has beennamed as LiOnHV , have been optimized and new steps have been achieved in order to set up suitable Reference Measuring Systems (RMSs) in order to allow:
• on-site verification of the accuracy of CTs and VTs by means of a purposely developed equipment, to be installed in HV network by means of live line working methods, without impact on normal service conditions;
• the identification of possible RMS architectures suitable for non-conventional instrument transformers and a preliminary evaluation of the associated uncertainty balances;
• the identification of possible sources and RMS architectures, suitable to characterize the behaviour of inductive instrument transformers when primary signal is affected by harmonics.The following important achievements have been obtained:
• an emergency system for the Simplified Transportable Disconnector (STD) of the LiOnHV equipment;
• the set-up of a prototype of a supply source and RMS suitable for the metrological characterization of inductive voltage transformers in presence of harmonics;
• a critical analysis of the RMS traditionally used for the calibration of low power instrument transformers having analogue output. The results obtained contribute to open new perspectives, not only from a purely metrological point of view but also and mainly within the frame of the regulation of electricity market and of supply, in its peculiar aspects of efficiency and quality, supporting the evolution of the research and of the standardization about this subject.

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