Investigation and modelling of sympathetic inrush due to transformer energization

Abstract

This paper presents a preliminary study of sympathetic inrush -a phenomenon when an already energized transformer experiences unexpected saturation during the energizing of another transformer connected in parallel. Power transformer can be saturated, giving rise to transients which lead to overvoltage and overcurrent. With the increase of distributed generations that can exaggerate more switching events, transients will become prevalent in such an operating environment. This can also bring power quality variation. Detailed MATLAB-Simulink models are developed and a small scale laboratory experiment using two parallel transformers has been set up to observe the sympathetic inrush interaction and the effect of pointon-wave switching. The simulation results are presented and the analytical calculations are shown to be validated by experiment.

Varying the energisation condition to mitigate sympathetic inrush current

“…There are negative impacts when the population of the network participants expands and the regularity of the network modifications which is the sympathetic inrush current is more noticeable and becomes more severe. Since the sympathetic inrush current occurs when the transformers are attached in parallel with the affected transformers [7], the sympathetic inrush current has not given top priority to investigate in the last few years. In a wind farm, wind turbine transformer (WTT) is vital machinery which operate as step-up transformers to connect grid system with the with the wind turbines.…”

“…The magnetising inrush current also can develop once energising a no-load transformer during the energisation [20], [21]. An earlier researchers discussed that the major characteristic of the magnetising inrush current is it spikes extremely high but progressively decays after a few cycles [17], [22] before the current drops to zero [7] as shown in Figure 2. Other than that, the value of magnetising inrush current can be several times greater than the rated current [6], [19], [23]- [25].…”

“…The sympathetic inrush current is divided into a few sections which influenced by a number of factors. There are consists of three factors which is system resistance, load and power factor and switching-on angle and a short explanation will be presented [7], [17], [22]. influenced by system resistance [32].…”

“…It is necessary to adjust the sympathetic inrush current growth by changing the value of the system resistance that might affect the sympathetic inrush current waveform. Other than that, the system resistance will reduce the magnitude of peak inrush current and quicken the inrush current decay [7]. As a result, it has been discovered that the higher system resistance, the sympathetic inrush will persist and develop more quickly.…”