Transformer Differential Protection Improved by Implementation of Negative-Sequence Currents
Abstract.
Existence of a relatively high negativesequence current is in itself a proof of a disturbance on the power system, possibly a fault. The paper describes the usage of the negative-sequence currents in order to both detect and positively determine the position of the fault with respect to the protected zone, and thus avoid some typical weaknesses of the power transformer differential protection. Some examples of these are long delays for heavy internal faults, unwanted operations for
external faults, and insensitivity to low-level turnto- turn faults, which can be left to develop into high-level faults – with more severe damage to the power transformer – before they can be detected.
Keywords.
Relay protection, power transformer, sensitive differential protection, negative-sequence currents, internal-external fault discriminator.
See detail : Transformer Differential Protection Improved by Implementation of Negative-Sequence Currents
