Measurement campaigns of the project 19NRM07 HV-com²
WP1 Definitions, software and instrumentation
Voltage Generators
New methods for generating reference combined and composite wave shapes in low voltage were studied. Three different low voltage calibrators from national labs, LNE, VTT, and TUBITAK have been built and validated. LNE technique is based on a linear high voltage and high-speed amplifier use to generate with only one block composite and combined voltage wave shapes. VTT solution consists of combining existing DC or AC calibrator with a calculable impulse voltage calibrator to generate composite voltage wave shapes. TUBITAK technique is based on the use ofblocking elements and combining existing DC or AC calibrator with an impulse voltage calibrator to generate composite voltage wave shapes. The calibrators performances were carefully tested and evaluated. The preliminary calibrators comparison allowed us to select one to take part in the inter-laboratory comparison that started in May 2022 for the recording instruments calibration. Using the voltage amplifier approach, a voltage level of 900 V in both polarities was reached for combined and composite wave shapes with a target uncertainty of 0.2 % for the peak value and less than 1% for the time parameters.
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LNE calibrator for combined and composite voltages based on a high voltage amplifier
Linear high voltage amplifier circuit
VTT Low voltage calibrator for composite voltages
VTT components of Low voltage calibrator for composite voltages
Circuit diagram of a DC and a calculable impulse voltage calibrator (series connection)
TUBITAK Low voltage calibrator for composite voltages
Waveforms collected from Industry
For the combined test voltage, the wave shapes to be evaluated are AC superimposed with LI or SI. Whereas, the wave shapes to be evaluated for composite voltage test are AC or DC superimposed with LI or SI. The required performance of the measuring systems depends on these wave shapes and should be carefully evaluated. In addition, software for the evaluation of the test voltage should also be able to evaluate the test voltage parameters with the required uncertainty.
Several combined and composite waveforms have been collected from industrial partners. These recordings have been evaluated using nine evaluation software developed by ten labs, VTT, TAU, PTB, FFII, LNE, RISE, INRIM, TUBITAK, TUG, and Haefely, based on different methods. The validation of the nine software has been done by comparing the evaluation results of the relevant parameters of the collected waveforms. The comparison of the waveforms parameters using evaluation software has led to the uncertainty estimation for combined and composite test voltages.
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Evaluation of AC superimposed with LI
Evaluation of AC superimposed with SI
Examples of composite waveforms collected from Industry
New evaluation software for combined and composite wave shapes
Composite voltage evaluation 1
Composite voltage evaluation 2
LVMI comparison on May – November 2022
For the combined and composite test voltages, no adequate traceability of these wave shapes exists. The requirements for approved measuring systems and their calibration are described in IEC 60060-2 but limited to the most used types of test voltages like DC, AC, LI, and SI. The performance evaluation of the recording instruments for combined and composite wave shapes depends on the ability of these devices to record both voltage components of the test object with a required resolution in time and amplitude. New calibration procedures of reference calibrators and recording instruments used to measure composite and combined wave shapes are under preparation and will be validated through an inter-laboratory comparison. A round-robin test is ongoing between seven labs, LNE, PTB, VTT, INRIM, Haefely, FFII, and TUBITAK, to qualify their digital recording instruments. These were optimized and characterised to fine-tune the performance. The comparison results will lead to measurement uncertainty evaluation for combined and composite wave shapes in low voltage at full scale. The traceability of the digital recording instruments will be created by setting up traceability methods.
Pictures of the Inter-laboratory comparison of LVMI
Experimental setup used to calibrate the digital recording instruments
Circuit diagram of the low voltage wave shapes generation and measurement
WP2: Traceable reference systems
Measurement campaign at PTB 27.06.2022 – 08.07.2022
The new modular universal voltage divider developed in this project was compared to two existing reference level universal voltage dividers. Comparison was carried out with different composite voltage combinations including both DC or AC superimposed with lightning or switching impulses up to 300 kV. The measured test voltage differences were less than 2 % meeting the project target uncertainty. Successful demonstration with combined voltages was also carried out to verify the operation of the dividers under such test.
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Setup at PTB measurement campaign
WP3: Existing measuring systems at testing laboratories
Measurement campaign at TU Graz 12.09.2022 – 23.09.2022
To assess the effects of composite voltages on linearity and measurement uncertainty of high voltage measurement systems based on universal dividers, a comparison campaign was carried out at Graz University of Technology in September 2022. During this campaign, the measurement results of two commercially available measurement systems from different manufacturers were compared with the reference measurement system designed in HV-com² project. In light of the increasing importance of HVDC equipment, the investigations were focused on the combination of DC and lightning as well as switching impulse voltages. The dividers were tested up to a DC voltage of 350 kV DC, with a maximum bipolar voltage stress of 1100 kV.
The investigations showed that a DC component does not lead to any significant effects regarding the measurement systems’ impulse voltage measurement performance, especially regarding the dynamic behaviour. All systems retained their high overall accuracy during all superimposed voltage tests. The obtained results will be used to investigate how universal voltage dividers intended for the measurement of superimposed voltages can be calibrated and how this process can be standardized.
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Team of the measurement campaign at TU Graz
Measurement campaign at TU Dresden 01.11.2022 – 15.11.2022
To verify the capability of onsite qualification of existing measuring systems for composite test voltages an additional comparison campaign was carried out at Technische Universität Dresden (TUD) with support from PTB in November 2022. During this campaign, the measurement results of one commercial measurement system used also during TU Graz campaign and an existing commercial measurement system from TUD for voltages up to 500 kV were compared with the reference measurement system designed within the HV-com² project. Measurements were carried out with DC, switching and lightning impulse voltages and their superposition. Subsequently the parameters peak voltage UP or test voltage Ut, time to peak TP or front time T1, time-to-half value T2 and the dc voltage U0 according to IEC 60060-1 were evaluated and compared between the measurement systems..
In some cases, the limits that were defined within the project were not fulfilled due to the deviation factors that were determined from the measurements. However, it could be shown that especially the time parameters are within the limits defined by IEC 60060-2 for pure voltage stress.
The deviation of the scale factors of the dividers used in this study was very small. Further tests showed that the different scale factors for each voltage type due to the calibration of the voltage dividers can lead to a larger deviation factor for the superposition of different voltages.
The obtained results will be used also to investigate how universal voltage dividers intended for the measurement of superimposed voltages can be qualified and how this process can be standardized.
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