Design of a digital protection scheme for power transformers using optimal state observers

Author

Murty, Y.V.V.S. ; Smolinski, W.J. ; Sivakumar, S.

Author_Institution

Dept. of Electr. Eng., New Brunswick Univ., Frederickton, NB, Canada

Volume

135

Issue

3

fYear

1988

fDate

5/1/1988 12:00:00 AM

Firstpage

224

Lastpage

230

Abstract

The authors present the design of a digital protection scheme for three-phase power transformers. The design is based on an optimal state observer for estimating the fundamental and harmonic components of the signals. The scheme provides primary protection for internal faults ground faults and backup protection for external faults. Internal fault protection is provided by means of a percentage differential characteristic, which also includes even- and fifth-harmonic restraints to prevent misoperation during inrush and overexcitation conditions, respectively. Protection for external faults is provided by means of a three-phase digital overcurrent relay. The protection scheme is implemented on a TMS320 digital signal processor and tested in the laboratory using a three-phase transformer. Relay operation times are in the range ¹/₂ to ³/₄ of a 60 Hz cycle for internal and ground faults. The percentage differential relay provides complete restraint during inrush, overexcitation and external fault conditions

Keywords

electrical engineering computing; power transformers; relay protection; state estimation; transformer protection; TMS320 digital signal processor; backup protection; digital protection scheme; even harmonic restraints; external faults; fifth-harmonic restraints; ground faults; internal faults; optimal state observers; percentage differential characteristic; power transformers; primary protection; three phase transformer; three-phase digital overcurrent relay;

fLanguage

English

Journal_Title

Generation, Transmission and Distribution, IEE Proceedings C

Publisher

iet

ISSN

0143-7046

Type

jour

Filename

6376