Power Transformer Protection

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A GO3-5005 EMarch 1988Power Transformer ProtectionApplication GuideAuthorR NylenSenior application engineer)ABB RelaysPower Transformer protectionAGO3-5005 EPage 2List of contents)1. INTRODUCTION2. CONDITlONS LEADING TO FAUL Insulation Aging of Overheating due to Oil contamination and Reduced cooling3. FAULT Ground faults in a solidly groundedstar-connected secondary Ground faults in a high impedancegrounded star-connectedsecondary Ground faults in a Turn-to-turn Phase-to-phase faults4. PROTECTIVE RELA Differential Differential relays for fully Differential relays for Overcurrent Protection andimpedance Time-overcurrent Under-impedance Distance Grou~d fault Low irrnpedance residualovercurrent Harmonic restraint High impedance restricted Low impedance restricted Tank Residual voltage Overexcitation Flashover and ground faultprotections for low voltag

winding. Theoretical inrush currentlm. Recorded inrush current for a 60 MV A transformer 140/40/6.6 kV. connected YNyd. Operating time. Through faun restraint. Magnetizing current at overexitation. Transformer differential relay for autotransformer. Differential relay RADHA or RADSG for autotransformer.

  Winding, Autotransformer