A wavelet-based technique for discrimination of inrush currents from faults in transformers coupled with finite element method

Abstract

The phenomenon of magnetizing inrush is a transient condition, which occurs primarily when a transformer is energized. The magnitude of inrush current may be as high as ten times or more times of transformer rated current that causes malfunction of protection system. So, for safe running of a transformer, it is necessary to distinguish inrush current from fault currents .In this paper, a wavelet-based technique has been used to discriminate inrush current from faults. For this purpose, a wavelet transform (WT) concept is presented and a criterion based on different behaviors of the differential currents under fault and inrush conditions have been derived. For checking the validity of the wavelet-based technique in discriminating of inrush currents from faults a three-phase 20/63 kV transformer has been simulated in Maxwell software that is based on finite element method (FEM). Then, obtained data from different situations have been used in MATALB software for implementation of the WT technique.

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

“…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). So, magnetic wall shunts are used to minimize stray losses in CT.…”

Magneto-Thermo-Structural Analysis of Power Transformers under Inrush and Short Circuit Conditions

“…Among the many transient events that cause failures, those caused by inrush and short-circuit currents are responsible for the majority of operation interruptions in transformers. The magnitude of inrush current may be as high as 10 times or more of transformer-rated current, which can cause malfunction of protection system [1]. Shortcircuit currents induce excessive forces in the transformer windings that result in deformities in the winding, affecting its mechanical and electrical characteristics [2].…”

A discrete wavelet transform approach to discriminating among inrush current, external fault, and internal fault in power transformer using low-frequency components differential current only

“…The idea of application of wavelet transform to fault diagnosis is not new, and there are a number of research papers related to this idea 11–27. In Ref.…”

“…[37], an online sweep frequency-response analysis (SFRA) was developed to detect winding interturn faults of power transformers in service using the transfer function method. The idea of application of wavelet transform to fault diagnosis is not new, and there are a number of research papers related to this idea [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27]. In Ref.…”

“…In the literature for fault detection, several decision algorithms 1–42 have been developed to be employed in the protective relay for preventing maloperation of the protective equipment under different nonfault conditions, including magnetizing inrush current, ratio mismatch, through‐fault current, etc. There are many techniques 1–42 for detecting faults, such as artificial neural networks (ANNs) 12,30,39,40, transient‐based protection 13,18–20, finite element 14, fuzzy logic 35, hybrid systems 14,32, and so on. An algorithm for protecting a transformer with three windings using the increments of flux linkages (IFLs) has been proposed by Kang et al 2.…”