A new technique to mitigate inrush current caused by transformer energization

Abstract

This paper presents a new method to mitigate inrush currents caused by transformer energization. The method uses a grounding resistor connected at the transformer neutral and delayed energization of each phase of the transformer. The proposed method was tested by PSCAD/EMTDC simulation and laboratory experiments. Both simulation and experimental result show that the proposed scheme has a performance similar to that of the resistor pre-insertion scheme, but it will be much less expensive since there is only one resistor involved. The level of the inrush current reduction depends of the value of the neutral resistance and of the transformer parameters.

A dynamic harmonic domain-based framework to detect 3-phase balanced systems under dynamic transients: the test case of inrush current in transformers

“…The circuit has a current source given by the current of Figure 7. The objective of this circuit is to obtain the current waveform flowing in each filter branch and to compare it with those waveforms originating from DHD by using Equation (7). On the other hand, the EMTP has the option of using a current source given by a set of points, so the EMTP was then used to simulate the circuit in Figure 9.…”

“…Although the transformer steady-state magnetization current is about 1% to 2% of the rated current value, it may increase up to 10 to 20 times of the rated value in case of energization owing to inrush currents. [5][6][7] Inrush currents are a transient phenomenon that increases sharply to peak value and injects significant harmonic contents to the grid, resulting in adverse operation conditions. It is known that they can cause unnecessary tripping of differential protection relays.…”

Mitigation of magnetising inrush current in three–phase power transformer

“…Many inrush current mitigation techniques have been proposed over the years each with its own advantages and disadvantages. From the past few years, research is going on to mitigate this current [6][7][8][9][10][11][12][13][14][15][16]. Controlled switching in transformer can possibly remove these transients if residual core is considered in the closing process [17][18].…”

Research of controlled switching strategy to restrain inrush current during the energisation of converter transformer

“…Inrush current is mainly affected by the iron core hysteresis characteristics, closing voltage phase angle, and residual flux. Traditional suppression methods use the series resistance, parallel capacitors, and other additional equipment to accelerate the transient inrush current attenuation process, but failed to fundamentally eliminate the inrush current [9]. With the advancement of switching technology, the controlled switching could completely eliminate the inrush current theoretically with no additional equipment investment [10].…”