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.