A novel digital non-electrical protection for power transformer based on internal pressure characteristics

Abstract

Power transformers play a very critical role in electrical energy transmission. Abnormal performance of transformers would seriously affect the reliability and stability of power system. Non-electrical gas relays are usually used as a main protection of power transformers. Indeed, due to the inherent defects, the gas relay misjudgments happen every year across the world. Given this background, this paper employs a theoretical model and its simulation method to study the relationship between electrical faults and non-electrical pressure variations inside the tank. Based on the essence difference of the pressure characteristics among the internal faults, external faults and normal running condition, a novel transformer protection principle is proposed. Numerical test has indicated that the proposed protection is able to reliably clear the transformer internal faults, even the single-turn fault or other weak faults.