Analysis and improvement of grounding transformer's ability to resist outlet short-circuit

Abstract

Currently, there are issues such as insufficient research on the physical characteristics of windings in grounding transformers under outlet short circuit conditions and a high number of damage accidents. Given this issues, a dry-type grounding transformer is chosen as the research subject. A three-dimensional multi-physics field coupling model is constructed using finite element simulation software. The aim is to analyze changes and distribution patterns of multiple physical parameters such as winding electromagnetic fields, winding temperature rise, and winding stress deformation under the outlet short circuit condition of the low voltage side of the grounding transformer. The key factors influencing grounding transformer's ability to resist outlet short circuit are also explored. Results indicate that after an outlet short circuit occurs in the grounding transformer, the magnetic flux and equivalent stress on its winding side, influenced by its yoke core and adjacent pillar cores, are greater than those on the front side, resulting in extremely uneven overall deformation. Due to the grounding transformer's special winding structure and operating mode, the transient temperature of its low voltage winding during outlet short circuit faults can reach 140.9 ℃, which is much higher than that of the high voltage winding. Finally, measures are proposed to improve the grounding transformer's ability to resist outlet short-circuit based on the dual constraints of dynamic and thermal stability, and structural optimization is carried out for the weak areas of grounding transformer to resist outlet short-circuit.

Keywords

• grounding transformer
• outlet short-circuit
• multi-physics field coupling
• winding deformation
• winding temperature rise
• improved short-circuit resistance