An Energy Variation-Based Method for Discrimination Between the Internal Fault and Inrush Current in Power Transformers

The main equipment responsible for connection and transmission of electric power from generating centers to consumers are power transformers. This type of equipment is subject to various types of faults that can affect its components, in some cases also compromising its operation and, consequently, the electric power supply. Thus, in this paper, electromagnetic, thermal, and structural analysis of power transformers was carried out with the objective of providing the operator with information on the ideal moment for performing predictive maintenance, avoiding unplanned shutdowns. For this, computational simulations were performed using the finite element method (FEM) and, from that, the different transformer operation ways, nominal currents, inrush current, and short-circuit current were analyzed. In this perspective, analyses of the effects that thermal expansion, axial forces, and radial forces exerted were carried out, contributing to possible defects in this type of equipment. As a study object, simulations were carried out on a 50 MVA single-phase transformer. It is important to emphasize that the simulations were validated with real data of measurements and with results presented in the current literature.

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Magnetic Inrush Current in Distributed Photovoltaic Grid Power Transformers

Distributed Photovoltaic Grid Transformers ◽

10.1201/b16412-13 ◽

2017 ◽

pp. 143-149

Keyword(s):

Power Transformers ◽

Inrush Current

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Numerical Differential Protection of Power Transformer using Innovative Algorithm

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.e1093.0785s319 ◽

2019 ◽

Vol 8 (5S3) ◽

pp. 438-446

Keyword(s):

Power Transformer ◽

Algorithm Design ◽

Point Of View ◽

Inrush Current ◽

Current Transformers ◽

Simulink Model ◽

Internal Fault ◽

Safety And Reliability ◽

Operating Current ◽

Primary Current

This paper presents a new innovative algorithm for Numerical Differential Relay design of transformer. Fault information is critical for operating and maintaining power networks. This algorithm provides accurate performance for transformer by which is independent of system conditions such as: External fault, Inrush current, CT saturation. Locating transformer faults quickly and accurately is very important for economy, safety and reliability point of view. Both fault-detection and protection indices are derived by using Numerical Differential Relay algorithm design of transformer. The embedded based differential and operating current measurement device is called numerical differential relay is among the most important development in the field of instantaneous fault operation. Numerical relay provides measurement of differential current and operating current at power transformer above 5MVA in substation. Simulation studies are carried out using MATLAB Software show that the proposed scheme provides a high accuracy and fast relay response in internal fault conditions. Current transformers form an important part of protective systems. Ideal Current Transformers (CTs) are expected to reflect the primary current faithfully on the secondary side. Under conditions the CT saturates, and hence it cannot reproduce the primary current faithfully. This paper deals with simulation methods for determining CT performance under different factor. A Simulink model has been developed to observe CT response under steady state w.r.t Burden, Turns ratio, Asymmetrical current, Hysteresis conditions. Thus, it is now possible to evaluate the CT performance under these factors

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Discrimination between internal fault and magnetising inrush currents of power transformers in the presence of a superconducting fault current limiter applied to the neutral point

IET Science Measurement & Technology ◽

10.1049/iet-smt.2015.0249 ◽

2016 ◽

Vol 10 (5) ◽

pp. 537-544 ◽

Cited By ~ 14

Author(s):

Ali Sahebi ◽

Haidar Samet

Keyword(s):

Neutral Point ◽

Power Transformers ◽

Fault Current ◽

Fault Current Limiter ◽

Superconducting Fault Current Limiter ◽

Internal Fault ◽

Inrush Currents ◽

Current Limiter

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Novel Remanence Determination for Power Transformers Based on Magnetizing Inductance Measurements

Energies ◽

10.3390/en12244616 ◽

2019 ◽

Vol 12 (24) ◽

pp. 4616

Author(s):

Chen Wei ◽

Xianqiang Li ◽

Ming Yang ◽

Zhiyuan Ma ◽

Hui Hou

Keyword(s):

Numerical Simulations ◽

Laboratory Experiments ◽

Power Transformer ◽

Power Transformers ◽

Inrush Current ◽

The Core ◽

Novel Method ◽

Simulation Results ◽

Electro Magnetic ◽

The Relationship

The remanence (residual flux) in the core of power transformers needs to be determined in advance to eliminate the inrush current during the process of re-energization. In this paper, a novel method is proposed to determine the residual flux based on the relationship between residual flux and the measured magnetizing inductance. The paper shows physical, numerical, and analytical explanations on the phenomenon that the magnetizing inductance decreases with the increase of residual flux under low excitation. Numerical simulations are performed by EMTP (Electro-Magnetic Transient Program) on a 1 kVA power transformer under different amounts of residual flux. The inductance–remanence curves are nearly the same when testing current changes. Laboratory experiments conducted on the same transformer are in line with the numerical simulations. Furthermore, numerical simulation results on a 240 MVA are reported to demonstrate the effectiveness of the proposed method.

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