Results of an International Comparison of Instrument Current Transformers up to 10 kA at 50 Hz Frequency

2021

Energies

In the framework of the empir projects myrails and windefcy, metas developed a primary standard for electrical power using commercial off-the-shelf components. The only custom part is the software that controls the sampling system and determines the amplitude and phase of the different frequency components of voltage and current. The system operates from dc up to 9 kHz, even with distorted signals. The basic system is limited to 700 V and 21 A. Its power uncertainty is 15 μW/VA at power frequencies and increases to 1.8 mW/VA at 9 kHz. With the extension up to 1000 V and 360 A, the system reaches power uncertainties of 20 μW/VA at power frequencies, increasing to 510 μW/VA at 9 kHz. For higher voltages or higher currents, the same principle is used. However, the uncertainties are dominated by the stability of the sources. The voltage and current channels can also be used independently to calibrate and test power quality instruments. Thanks to a time-stamping system, the system can also be used to calibrate phasor measurement units, which are synchronised to utc.

Section: Extension Using Amplifiers and Step-up Transformersmentioning

confidence: 99%

Sampling Primary Power Standard from DC up to 9 kHz Using Commercial Off-The-Shelf Components

2021

Energies

Section: Extension Using Amplifiers and Step-up Transformersmentioning

confidence: 99%

Sampling primary power standard from DC up to 9 kHz using commercial off-the-shelf components

2020 3rd International Colloquium on Intelligent Grid Metrology (SMAGRIMET)

2020

“…They can be designed for such transformers with differences below 50 × 10 −6 and reach uncertainties below 0.01 × 10 −6 . Most participants in the last European current transformer comparison used bridges [5].…”

Section: Introductionmentioning

confidence: 99%

Optimised calibration programmes for comparators for instrument transformers

Tm - Technisches Messen

2021

Traditionally, instrument transformers are calibrated using bridges. By definition, bridges use the null method of measurement. The traditional calibration programme for instrument transformer bridges characterise namely this null measurement. Many new commercial comparators for instrument transformer use a very different method. They sample the secondary signals of reference and device under test (dut) transformer independently. Based on the samples, magnitude and phase of both signals are determined. Ratio error and phase displacement are calculated. Consequently, the significance of their calibration using the traditional calibration programme is limited. Moreover, the operating range of modern comparators is much larger than that of bridges. The additional versatility cannot be used without an adapted calibration programme. This article analyses the calibration programmes for both technologies. An experimental study confirms both the suitability of the new calibration programme and the need to chose the calibration programme depending on the technology of the device to be calibrated. The conclusion is very general and applies to all measurement problems where an operating principle is replaced by another – when changing the operating principle, it is important to check the calibration programme and adapt it if necessary.