Development of a Wideband Current-to-Voltage Transformer Set for Currents up to 2 kA

Abstract

This paper describes the setup and characterization of a set of wideband Current-to-Voltage (C-to-V) transformers equipped with symmetrical primary windings. The objective is to use the C-to-V transformer set to calibrate digital instrument transformer (IT) accurately at power frequency and within a wider frequency range to cover power quality aspects. The errors of the 50 A and the 200 A reference current transformer (CT) were within ±10 ppm and μrad at 50 Hz. The frequency responses of the two CTs up to 12 kHz were below 0.1 % and 0.2 crad.

Traceable calibration system for non-conventional current sensors with analogue or digital output

“…1. high current generation system (marked as red block), a set of analogue reference CTs (marked as green block) with associated precision resistors [8] and a precision 2-channel measuring system (marked as purple block) [9], [10]. The synchronization signals (marked as "Sync."…”

“…The rated primary currents of the C-to-V transformer set ranges from 8.3 A to 1500 A. Four commercial zero-flux CTs with rated currents of 50 A (CT50), 200 A (CT200 [8]), 600 A (CT600) and 2 kA (CT1500) were used to establish the reference CTs . To convert the different secondary currents of these CTs into a 1 V output voltage, a resistor box was built, containing six precision resistors from 1 Ω to 20 Ω.…”

“…7 (below). According to the previous work [8], the characterisation of the C-to-V transformers was carried out by separating the behaviour at power frequency and the frequency response. The errors of the current transformers (εi(f) and δi(f)) are represented by εi(f) = εi(f0) + Δεi(f) and δi(f) = δi(f0) + Δδi(f), where εi(f0) and δi(f0) refer to the CT errors at power frequency and Δεi(f) and Δδi(f) refer to the frequency response of the CTs.…”

Measurement Methods and Procedures for Assessing Accuracy of Instrument Transformers for Power Quality Measurements

“…Study and definition of ITs errors and uncertainty contributions in the PQ phenomena measurement require that suitable systems are developed, to enable the characterization of ITs with reference waveforms representative of the actual disturbances of PQ. Starting from knowledge gathered in past projects [2]- [5], existing laboratory set-ups will be modified, extended and integrated into reference systems for the traceable calibration of current and voltage ITs, under realistic PQ phenomena. They will allow characterization of different technologies of current and voltage ITs, from the still extensively used inductive ITs to the more recent generation of Low Power Instrument Transformers (LPIT) with analog or digital output.…”