Development of Inductive Current Transformer 400/5/1 of Class 0.2S for Frequency Range 50 Hz-5 kHz

Area of Science:

• Electrical Engineering
• Materials Science

Background:

• Accurate current measurement is crucial in power systems, especially with increasing harmonic distortion.
• Traditional inductive current transformers (iCTs) often struggle to maintain accuracy across a wide frequency range.
• Developing wideband iCTs is essential for advanced power quality monitoring and protection.

Purpose of the Study:

• To design and develop a window-type inductive current transformer (iCT) with a 400 A rated primary current.
• To achieve a 0.2S accuracy class for sinusoidal and distorted currents from 50 Hz to 5 kHz.
• To evaluate and select optimal magnetic core materials for wideband iCT applications.

Main Methods:

• Design and simulation of a window-type iCT with dual secondary windings (5 A and 1 A).
• Analysis of wideband magnetic properties of electrical steel, permalloy, and nanocrystalline (Nano) materials.
• Experimental testing of four nanocrystalline cores with varying initial magnetic permeabilities.
• Verification of current error and phase displacement against 0.2S accuracy class limits.

Main Results:

• The developed iCT met the 0.2S accuracy class requirements for both 50 Hz sinusoidal and distorted currents up to 5 kHz.
• Nanocrystalline (Nano) magnetic cores were identified as the most suitable material due to their wideband properties.
• Higher initial magnetic permeability in nanocrystalline cores led to increased active power losses, making them less ideal for 50/60 Hz operation.

Conclusions:

• A novel window-type iCT capable of high accuracy across a wide frequency spectrum (50 Hz - 5 kHz) has been successfully developed.
• Nanocrystalline cores offer a viable solution for wideband inductive current transformers, though material selection requires careful consideration of operating frequencies.
• The findings provide valuable insights for designing advanced current measurement devices for modern power grids with significant harmonic content.