When Existing Recommendations for PST Protection can Let you Down

Description

Z. GAJIĆ, ABB SA Products, Sweden M. PODBOJ, ABB, Slovenia B. TRAVEN, ELES, Slovenia A. KRAŠOVEC, Istrabenz Gorenje, Slovenia [email protected] paper will present implemented protection scheme on two, symmetrical, double core design Phase Shifting Transformers (PST) [6], each rated at 600MVA, 400kV, 866A, 50Hz, ±40º with in total 64 tap positions (32 advance and 32 retard). Thus, every individual tap introduce phase angle shift of 1,25º. The used PST protection scheme follows the protection recommendations published by IEEE. It shall be noted that this IEEE recommendation is mainly based on information available in reference. However during execution of this project new challenges were faced due to following reasons: Slightly different construction of PST Numerical differential relays are used instead of electro-mechanical ones originally suggested in Due to these differences this paper will: Indicate at which statements IEEE publication [1] is wrong due to slightly different PST design Provide design and setting guidelines for 87P and 87S functions when modern numerical transformer differential protection is used.