Time-Domain Differential Protection Method Applied to Transmission Lines

This paper presents a time-domain protection solution based on integrated quantities. In order to provide a deterministic differential protection method, two algorithms that use voltage and current samples to estimate energy flow and reactive power entering a protection zone are used. The algorithms work by integrating time-domain measurements and generated signals in order to achieve stable quantities that are afterwards used for protection. After the description of the differential fault identification method, a phase selection scheme is presented in order to provide a complete protection solution. The proposed system was extensively tested on simulations based on data from five actual transmission lines, the power systems were simulated using ATP/EMTP and the protection was implemented using GNU Octave software. Thousands of cases were generated using automation scripts in order to validate the protection algorithms. The work also describes the conducted sensitivity test, which includes current transformer saturation and unsynchronized measurements. The proposed solution proved itself secure and dependable under the tested conditions.