Implementation and Analysis of a Digital Model of the Incremental-Quantity Distance Element Using EMTP

This paper discusses the governing principles and overall design of the incremental-quantity distance element pre-sent in commercially available time-domain-based protective relays (TDRs), as well as the details pertaining to the digital im-plementation of this element using the Electromagnetic Transi-ents Program (EMTP). Analysis of the performance of this ele-ment under various fault scenarios is presented as well. It also discusses the limitations of the model, along with some of the assumptions that were made during its implementation in EMTP. The model is validated using a commercially available TDR by utilizing the event-playback testing capabilities of these modern relays. This new capability is utilized not only in the performance analysis testing, but also in the core functionality design of the digital model. The principal advantage of this modern time-domain-based approach to power system protection is the speed at which the protection elements can operate after a fault is sensed on a transmission line. The rapid operating time gives this protection technique a competitive edge over traditional phasor-domain impedance-based protection schemes from which these modern techniques are derived.