Effect of Primary Cable Position on Accuracy in Non-Toroidal-Shaped Pass-Through Current Transformer.

Area of Science:

• Electrical Engineering
• Electromagnetics
• Power Systems

Background:

• Non-toroidal current transformers (CTs) offer advantages for high-current measurement due to their large airgap, allowing multiple cables per phase.
• The positioning of primary current-carrying cables within the CT window is critical for accurate operation.
• Non-uniform magnetic fields can arise from off-center cable placement, potentially leading to local core saturation.

Purpose of the Study:

• To investigate the influence of primary cable positioning on the performance of non-toroidal protection CTs.
• To identify the conditions under which partial saturation occurs in these CTs.
• To determine the acceptable region for cable placement to maintain CT accuracy.

Main Methods:

• Finite Element Analysis (FEA) was employed to simulate magnetic field distribution and identify areas of core saturation.
• Experimental tests were conducted on non-toroidal protection CTs with varying cable positions.
• Measurements were taken for currents up to 5 kA to validate simulation results.

Main Results:

• FEA simulations confirmed that off-center cable positions induce partial saturation in specific areas of the magnetic core.
• The study delineated the admissible region for cable positioning to ensure accurate CT performance.
• Experimental validation corroborated the FEA findings, demonstrating the impact of cable placement on CT accuracy.

Conclusions:

• The position of primary cables is a critical factor affecting the accuracy of non-toroidal protection CTs.
• Deviations from optimal cable positioning can lead to partial saturation and inaccurate current ratio.
• Proper installation guidelines based on FEA and experimental data are essential for reliable operation of these CTs.