Transformer Inrush Current Mitigation Using Controlled Switching and Magnetic Flux Shunts

Abstract

Abstract:The inrush current is a transient current that results from a sudden change in the exciting voltage across a transformer's windings. It may cause inadvertent operation of the protective relay system and necessitate strengthening of the transformer's mechanical structure. Many methods were reported in the literatures for reduction and mitigation of transformer inrush currents. This paper represents a study of techniques that have been proposed for transformer inrush current mitigation. A new, simple and low cost technique to reduce inrush currents caused by transformer energization is presented here. In this method, a controlled switching approach with a grounding resistor connected to transformer neutral point and a magnetic flux shunt is used. By energizing each phase of the transformer in sequence, the neutral resistor behaves as a series-inserted resistor and thereby significantly reduces the inrush currents. The dimensions of the magnetic flux shunts are chosen such that the inrush current amplitude is further reduced. The proposed method has been tested by computer simulation using 2-D FEM (two-dimensional finite element method) by Maxwell software. The obtained results show that the proposed method is efficient in reduction of transformer inrush current and is much less expensive since there is only one resistor involved and the resistor carries only a small neutral current in steady-state.

Point on Wave Energization Strategy and Sequential Phase Shifting for Sympathetic Inrush Current Mitigation in Three-Phase Transformer - Measurement

“…This technique is considered new in this field. There is also a simple technique based on the integration of a resistance in the neutral of the three-phase transformer, this technique is proposed in (Arand, 2013;Abdulsalam et al, 2017;Abdelsalam et al, 2015;Cui et al , 2005). This is not enough but the authors exploit the phase shift of the three phases to create a sequential excitation.…”

Inrush Current Reduction by a Point-on-wave Energization Strategy and Sequential Phase Shifting in Three-Phase Transformer

“…Cheng et al [8] presented a new approach where they modified the transformer coil distribution. Arand et al [9], Abdulsalam, and Xu [10], Abdelsalam and Abdelaziz [11] and Cui et al [12] suggested a simple technique by the insertion of a resistance between the neutral of the transformer and the ground, taking into account the sequential energization of the three phases. Using an existing photovoltaic generator.…”

Modified method for transformer magnetizing characteristic computation and point‐on‐wave control switching for inrush current mitigation

“…A new approach was presented in Cheng et al based on changing the distribution of the coil windings to increase the transient inductance and hence limit the inrush current. Arand et al, Abdulsalam and Xu, Cui et al, and Xu et al proposed a simple method based on inserting a resistor in the neutral of the transformer, and with the sequential energization of each phase. Abdelsalam and Abdelaziz studied the reduction of the inrush current by the existing photovoltaic source; the reduction was achieved applying an opposite flux, taking into account the switching instant.…”