Inrush Currents In Three-phase Transformers Research Articles

Reduction of Three-Phase Transformer Inrush Currents Using Controlled Switching

This article proposes a new approach for reducing inrush currents in three-phase three-legged stacked-core power transformers. Although magnitudes of inrush currents may not be as high as short-circuit currents, they are extremely detrimental to normal operation of power transformers. In this article, a new controlled switching scheme that takes into consideration both core saturation and residual flux is proposed to reduce inrush currents. Also, a transient model based on the duality transformation between electric and magnetic circuits is proposed, where a nonlinear inductance is used to simulate core saturation. The proposed scheme is demonstrated on a real transformer by both laboratory experiments and performing simulations. The Alternative Transients Program is used to simulate a wide spectrum of possible operating conditions. The experimental and simulation results show that inrush currents are significantly reduced after utilizing the proposed scheme. Therefore, the proposed controlled switching scheme will result in relaxing inrush-current-related constraints in designing and manufacturing three-phase power transformers, which, in turn, will reduce their cost.

An Adaptive Approach for Simulation of Inrush Current in Three-phase Transformers Considering Hysteresis Effects

This article proposes a novel adaptive approach for accurate simulation of inrush currents in three-phase power transformers. The proposed technique is based on using artificial neural networks to update inverse Jiles–Atherton hysteresis model parameters during inrush current transients. The required parameters for training artificial neural networks are obtained using particle swarm optimization based on measured inrush current waveforms. The results show that the proposed technique can be used for accurate simulation of this phenomenon in three-phase power transformers. Inrush current measurements on a three-phase three-leg transformer are used for artificial neural network training and verification of the results.

Simulation of three-phase transformer inrush currents by using backward and numerical differentiation formulae

This paper presents a simplified model of a three-phase transformer developed in the state-space form using the linear graph theory. The algorithm for generating the coefficient matrixes of the state-space equation is described. Stiff detection procedures of differential equation systems that describe the three-phase transformer inrush current transients are explained. It is shown that the time-domain transient response of three-phase transformers mathematically describes extremely stiff systems. The numerical integration methods based on strong stable (A and L) backward differentiation formulae are used to solve extremely stiff differential equation systems arising from the state-space formulation of the transformer inrush current transient equations. A comparison of the measured and simulated three-phase transformer inrush currents showed very good agreement. The proposed procedure of modeling and the simulation method are useful tools that can be applied to other electrical transients where extremely stiff systems appear.

04/01658 Utilizing Preisach models of hysteresis in the computation of three-phase transformer inrush currents: Adly, A. A. et al. Electric Power Systems Research, 2003, 65, (3), 233–238

04/01658 Utilizing Preisach models of hysteresis in the computation of three-phase transformer inrush currents: Adly, A. A. et al. Electric Power Systems Research, 2003, 65, (3), 233–238

Utilizing Preisach models of hysteresis in the computation of three-phase transformer inrush currents

A new approach through which transformer magnetizing inrush currents associated with the energization of three-phase transformers may be computed while accurately taking the effect of hysteresis into consideration. Transformer operating conditions such as switching-on angle and residual flux are also included. The simulation results are compared with those obtained experimentally in a laboratory model transformer.

95/00475 Calculation and harmonic analysis of transient inrush currents in three-phase transformers

95/00475 Calculation and harmonic analysis of transient inrush currents in three-phase transformers

Calculation and harmonic analysis of transient inrush currents in three-phase transformers

Measurements of transient inrush currents in three-phase transformers offer important data for power system operation and protection. Because three-phase transformers are more widely used in industrial applications than single-phase transformers, the inrush current of the three-phase transformer is worthy of investigation. This paper proposes a simple method, extended from that for single-phase transformers, to investigate three-phase transformer inrush currents. Harmonic analysis of the inrush currents is carried out. Various structures of three-phase transformers, including winding connections and loading conditions, are discussed. The simulation results are compared with experimental results. The proposed method is simple and effective for transformer banks and five-limb transformers. The harmonic analysis of inrush currents is useful for protective relay design.

Finite element analysis of inrush currents in three-phase transformers

A new method for analyzing inrush currents in transformers is conceived by modifying the finite element method. Using this method, the detailed behaviour of the transient flux can be analyzed taking into account the residual magnetism and three-dimensional leakage flux. The new method is especially effective in the calculation of the inrush currents of three-phase transformers. The inrush currents are examined experimentally by using a new method for measuring the residual magnetism and an equipment which controls switching angles.