Sharif Digital Repository

The goal of this master thesis is to develop a new accurate numerical algorithm for digital differential relay to protect a power transformer. This work employs specially developed software to simplify its input signal processing task which helps to quickly and accurately detect and clear the transformer internal faults. The available commercial transformer digital differential relays lack the required sensitivity to detect turn to turn faults when a few numbers of turns (less than 10% of the winding) are involved. This work presents a new equivalent circuit for transformer when a turn to turn fault occurs on either winding. This equivalent circuit helped to develop an accurate algorithm for... 

One of the most critical equipments in power grids are power transformers, which are vulnerable to damage due to the possibility of faults in its various components. A very common category of such faults is turn-to-turn fault in its winding. This fault initiates by the aging of the winding insulation with a short circuit of several adjacent loops to each other and if it is not detected quickly by the transformer protection, it will spread rapidly and can lead to irreparable failure in the transformer. Traditionally, turn-to-turn fault should be detected by mechanical pressure relays, however, due to the poor performance of these relays in the rapid detection of this type of fault, in the... 

Power transformer is one of the most important equipment in the power system which plays a key role in the reliability and quality of power delivery. Among numerous failure modes of a typical power transformer, the turn-to-turn fault (TTF) is one of the most prominent reasons for its unplanned outage. A turn-to-turn fault quite often begins with the degradation of the winding insulation between two adjacent turns, then in a short time, this low-level fault can progress to a large number of turns and results in the transformer costly damages. Therefore, it is vital to detect TTF at an early stage and prevent its progression to a catastrophic disaster. The conventional percentage differential...