Analysis of Stray Losses Calculation in Auto-Transformer Using Coupled IEM and FEM Technique

Abstract

Transformers are classified among the most important building blocks of any electric power system network. Transmission and Distribution losses are among the main thing that is emphasized and is taken into consideration by demands of the customer. The T & D loss varies in a range of 10 to 40% which is considered to be significant high. In a process of reducing total T & D losses, Loss capitalization for the modern age transformers has increased in a great extent. This indicates necessity of reducing losses (i.e. no load loss and load loss). Stray losses in the transformer contribute around 15 to 40% in the load losses which is considered to be a significant amount. Hence to match the loss capitalization stray losses shall be reduced. This is achieved by controlling the leakage field. Large rating transformers are with strong electromagnetic field; If the field is not controlled it links with the various structural parts of the transformer and will result in to excessive loss concentration, local heating (i.e. hot spots) and further gasification during service conditions. Various measures e.g. magnetic and nonmagnetic shields are known to control the stray field in the transformers. Effective solution needs to be selected to make shielding measure more optimum. This paper presents a case study involving estimation of stray losses in a 200 MVA, 220/132/11kV Auto transformer using an Integral Equation Method (IEM) and Finite Element Method (FEM) based EDMAG-3D software program.