Detection of Inrush Current in Transformers Based on Instantaneous Reactive Power
D P Balachandran1, R Sreerama Kumar2, B Jayanand3
1Dr. D P Balachandran, Professor in EEE Mar Baselios College of Engineering Trivandrum, Kerala.
2Dr. R Sreerama, Kumar vice Presidency projects, King Abdul Aziz University, Jeddah, Saudi Arbia.
3Dr. B Jayanand, Professor in EEE Govt. Engineering College Thrissur, Kerala, India.
Manuscript received on January 22, 2015. | Revised Manuscript received on February 18, 2015. | Manuscript published on February 28, 2015. PP: 189-192  | Volume-4 Issue-3, February 2015. | Retrieval Number:  C3807024315/2013©BEIESP

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Abstract: When a transformer is energized on no load there is a transient inrush current which causes mal-operation of protective relays. The challenge is to distinguish the inrush current from load and fault currents. In this paper, a new technique, based on instantaneous reactive power theory is proposed for the detection of inrush current in single-phase transformers. During inrush current as the lower order harmonics are significant, the average value of instantaneous reactive power becomes negative, and hence this feature is utilized in this paper to distinguish inrush currents from other currents. Investigations are carried out for different faults and switching conditions on a single-phase transformer using PSCAD software. The simulation results show that the proposed method is able to effectively identify inrush currents from other currents.
Keywords: Inrush current, Transformer faults, Instantaneous reactive power.