Stray Load Loss Valuation in Electrical Transformers: A Review

Abstract

The electricity production opus in South Africa has transformed over the last few years from predominantly coal power generation to a blend of renewable energy generation. The necessity emerges to ascertain whether electrical transformer design philosophies in local manufacturers are contemporary in reference to customer specifications, under increasing penetration of harmonics and distortion as a result of increasing deployment of decentralized power systems. Accurate computation of transformer stray load loss is imperative in localizing the hotspot regions and design of adequate insulation system and consequently cooling system. This loss must also be met by manufacturers based on the customer specifications to avoid penalties. The review of current scientific works affirms the ongoing interest in utilizing the advancement of computational power for painstaking evaluation and management of stray load loss in electric transformers. This article confers overview research, evolution and application of diverse computer-based tools for analyzing the stray load loss based on over 60 published scientific works. Mathematical formulations that can be practically employed by transformer designers during the design phase under normal and harmonic load current conditions are discussed.

Multi-Objective Design Optimization for HVDC-LCC Converter Transformers: Analytical and FEA-Based Comparison

“…The number of parallel cables (paral) defines the winding radial width (RR). A disc winding type can have several turns in the same disc, and the radial width is defined by the number of parallel cables (paral) combined with the number of turns per disc (ndisc) [12]. The symbols used for each parameter described are detailed in Table III.…”

“…Thus, the core losses are a result of the product of the weight GFe times the magnetic losses Pmag (12).…”

Real‐time monitoring of transformer hot‐spot temperature based on nameplate data

“…where R eq_re f , R dc_re f and R TSL_re f are the total winding resistance in the equivalent circuit, its dc component and the value corresponding to the stray losses, respectively. Stray loss is defined as the loss caused by leakage flux in the windings, core, and other metallic parts such as clamps, magnetic shields, and tank walls [20]. Therefore, the total stray loss is split into two components of the windings eddy current loss P ew and the stray loss in the metallic parts other than the windings P osl .…”

“…Stray loss is defined as the loss caused by leakage flux in the windings, core, and other metallic parts such as clamps, magnetic shields, and tank walls [20]. Therefore, the total stray loss is split into two components of the windings eddy current loss $${P_{ew}}$$ and the stray loss in the metallic parts other than the windings $${P_{osl}}$$.…”

Improvement in Efficiency of Converter Transformer by The Reduction of Stray Losses

“…Stray losses occur in the transformer's metal parts due to leakage field produced by the winding in nearer metal parts i.e. tank (Moghaddami, Sarwat, and De Leon 2016, Del Vecchio et al 2017, Basak and Kendall 1987, Kuczmann, Szücs, and Kovács , Hajiaghasi, Abbaszadeh, and Salemnia 2019, Thango and Bokoro 2022. These stray losses are nearly 10% to 15% of the total losses, which causes local hot-spot of temperature rise in transformer (Li et al 2015, Janić, Valković, and Štih 2006, Orosz et al 2015, Jamali, Mirzaie, and Gholamian 2011.CT's secondary and tertiary winding is connected to the bridge rectifier and due to the sequence operation of switches in bridge rectifier, the current flow through the CT's winding is non-sinusoidal (Kulkarni andKhaparde 2004, Kothavade andKundu 2021); therefore, the losses are larger than in a normal transformer (Orosz, Borbély, andTamus 2017, Miguéis, Guimarães, andBorges 2017).…”