| Abstract [eng] |
The goal of this work is to explore the power transformers at the time of activation, currents prevailing on the moment of transition and to identify their potential effects on faulty activation of differential protection. Protection of high-voltage power transformers is based on residual current. This protection levels out the currents of the transformer at the beginning and end. Its operation is based on the disconnection of the protected device, when differential current reaches the maximum value of the current imbalance. However, when the power transformer is connected to the mains, the current saturating the core greatly increases during the transition process. This current consists of a number of higher current harmonics. This increases the imbalance current and possible faulty disconnection of the device. To ensure the accurate operation of relay protection and automation devices, the transition process must be must be assessed. It is necessary to determine the maximum possible imbalance current and the upper harmonics of the second level prevailing at the time. Tasks of research: Analysis of information sources was performed, the transformer operating principle was clarified, possible failures and protections used were identified. The real experimental study was performed for the chosen three-phase power transformers and the transition process of the transformer during its connection to the network was studied. An experimental study was carried out and the transition process of the transformer during its connection to the network was studied by performing the test with the MATLAB program. The stabilized differential protection tripping characteristic was drafted and operation/failure of the differential protection on the moment of activation of transformer was tested. Conclusions were made, the list of references is indicated. |
