Usage of inrush current surge for early detection of inter-winding faults

This paper presents the development of micro-processor based device for improving the sensitivity of differential protection of power transformers. Power transformers failure may lead to high scale system´s operations disruption and heavy economic losses, that´s why the lever of requirements for power transformer protections is so high. Differential protection is usually used as a main protection against internal faults such as inter-windings faults, inter-coil faults or coil-core faults. For safe protection against incomplete winding faults protection device must be capable to detect differential current from such a very low value from nominal. The idea for a new device is to use information extracted from inrush current thru Fourier transformation to perform an early detection of faults usually hardly detectable due to very low impact on transformer´s primary current in steady condition. In case of fault device may operate with much higher sensitivity thus sensing fault on its early stage.