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1. (WO2018122632) A METHOD FOR DETECTING INRUSH AND CT SATURATION AND AN INTELIGENT ELECTRONIC DEVICE THERFOR

Pub. No.:    WO/2018/122632    International Application No.:    PCT/IB2017/054658
Publication Date: Fri Jul 06 01:59:59 CEST 2018 International Filing Date: Tue Aug 01 01:59:59 CEST 2017
IPC: H02H 1/00
G01R 15/18
H02H 3/28
H02H 7/045
H02H 1/04
Applicants: ABB SCHWEIZ AG
Inventors: VALSAN, Simi
GUPTA, Arinjai
Title: A METHOD FOR DETECTING INRUSH AND CT SATURATION AND AN INTELIGENT ELECTRONIC DEVICE THERFOR
Abstract:
The present invention relates to a method for detecting CT saturation during inrush. The method comprising, computing an estimated sampled value of a current signal from a CT at a first time instance using sampled values of the current signal (220); determining an error from difference between the estimated sampled value of the current signal and a sampled value of current signal at the first time instance(230); identify a deviation in the sampled value of the current signal based on comparing the error to a first threshold (240); applying wavelet filtering on the sampled values to obtain frequency contents (250); comparing the frequency contents with a second threshold to detect an inrush condition (260); computing rate of change in sampled values occurring between the inception of deviation and the detected inrush condition (270) and detecting a saturation in the current transformer on exceeding a predefined third threshold value by the computed rate of change in the sampled values.