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Closing a transformer without load will lead to the emergence of sympathetic inrush current in adjacent transformer. Sympathetic inrush current always causes mal-operation of protective relay and harmonic over-voltage. Based on simplified equivalent circuit of two shunt-wound transformers, the magnetic analytical expression and rule of bias magnet attenuation are analyzed. After that, the reasons...
The first part of each digital protective relay is data acquisition system (DAS). DAS receives voltage and current signals from current transformers (CTs) and capacitive voltage transformers (CVTs) and prepares the inputs to the main board after some pre-processing. CTs and CVTs provide instrument level current and voltage signals to meters and protective relays in high voltage (HV) and extra high...
Current transformer (CT) saturation can cause protective relay mal-operation or even prevent tripping. The wave shape of the secondary current is severely distorted as the CT is forced into deep saturation when the residual flux in the core adds to the flux change caused by faults. In this paper, a morphological lifting scheme is proposed to extract features contained in the waveform of the signal...
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