Power Transformer and Environment Protection Enhancement.

The power transformer is considered not only as a vital and expensive component in power grid; but also the most dangerous element. Since it contains a great quantity of oil or gas SF6 in contact with high voltage elements, it may produce the risk of fire and explosion in case of abnormal circumstances or technical failures and hence affects on the envorinment. A differential protective relay that is very sensitive protection is generally used for protecting this power transformer. However, its operation may be affected by the disturbances such as inrush current, current transformer saturation and over-excitation due to external faults. Accordingly, false trips (mal-operation) of protective relay may be resulted in. This research work proposes root cause analysis based on fault tree analysis to be used for assessing disturbances that lead to false trips. When the critical root causes are identified, mitigation measures may be used. The model of security can help to quantify analytically the reliability of the considered protective relay and hence reinforcing it in order to reduce the failure risk. [ABSTRACT FROM AUTHOR]