A Novel Flux-Based Protection Scheme for Power Transformers

Document Type : Research Article


1 Assistant Professor, Department of Electrical Eng, Abbaspour School of Engineering, Shahid Beheshti University, Tehran, Iran

2 M.Sc. Student, Department of Electrical Eng, Abbaspour School of Engineering, Shahid Beheshti University, Tehran, Iran

3 B.Sc. Student, Department of Electrical Eng, Abbaspour School of Engineering, Shahid Beheshti University, Tehran, Iran


Internal Turn-Turn faults (TTF) are the most common failures in power transformers, which could
seriously reduce their life expectancy. Although common protection schemes such as current-based
differential protection are able to detect some of the internal faults, some other minor ones (such as TTFs and
short circuit near the neutral point) cannot be detected by such schemes. Likewise, these relays may have
false trip due to energizing inrush currents, transformer over excitation, and occurrence of CT saturation at
one side. In this paper, a novel Linkage Flux Based (LFB) scheme is proposed to detect TTF in power
transformers, which uses some Search Coils (SC) located on the transformer legs to sense the related linkage
flux. Any difference in induced voltage in the corresponding SCs (located on any leg) suggests passing
unsymmetrical linkage fluxes through them (unlike the normal conditions), which stands for the occurrence
of a fault inside the transformer. The proposed technique not only can be used to protect power transformers,
but also can be employed to find the fault location during repair activities, as well.


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