Open AccessNew approach to improve sensitivity of differential and restricted earth fault protections for industrial transformers
Author(s) -
Ghanbari Teymoor,
Samet Haidar,
Ghafourifard Javad
Publication year - 2016
Publication title -
iet generation, transmission and distribution
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.92
H-Index - 110
eISSN - 1751-8695
pISSN - 1751-8687
DOI - 10.1049/iet-gtd.2015.1343
Subject(s) - transformer , resistor , fault current limiter , current transformer , protective relay , electrical engineering , power system protection , ground , engineering , differential protection , reliability engineering , electronic engineering , electric power system , computer science , power (physics) , voltage , physics , quantum mechanics
Differential relays are the main protection for power transformers including transmission and industrial transformers. Protection against internal fault is generally relegated to these relays. The most probable internal fault of the industrial transformer is phase to ground type. To limit the fault current in this condition, a limiter resistor is utilised in the transformer. However, it has considerable impact on sensitivity of the differential and restricted earth fault (REF) protections. In this study, an effective approach is proposed to improve the differential and REF protections sensitivity of the industrial transformers. The proposed technique not only realises the fault current limitation function, but preserves sensitivity of the protections. In this method, a developed fault current limiter is utilised in the transformer neutral instead of the neutral grounding resistor. The performance of the proposed technique is evaluated by some simulations and experiments. The results confirm the high capability of the proposed technique in different conditions.