This paper presents a new fault detection algorithm based on the Fast Discrete Stockwell Transform. The algorithm can improve the functionality of existing distance protection and resolve shortcomings identified during the fault detection process in case of fault occurrence in systems with a high penetration of power electronics-based generators. Reported results of the operation of commercial distance relays of four different vendors show that all relays experience difficulties during ungrounded faults. An RTDS testbed is developed for extensive hardware in the loop testing, comprising electromagnetic transient models of Type-3 and Type-4 wind generators. The proposed algorithm successfully overcomes the identified problems for cases where commercial relays maloperate. The threshold parameters for the fault detection are set by using the energy content attributed to the Fast Discrete Stockwell Transform time–frequency domain signal. Other distance protection modules such as the determination of directionality, phase selection and the computation of the impedance, which are necessary for the protection selectivity, are developed based on currently available solutions applied in commercial relays. The new algorithm has been extensively tested using RTDS for various fault conditions and the obtained results are reported in the paper.@en

This paper deals with a comprehensive analysis to test the performance of available distance protection, that can be used in transmission networks with high penetration of converter-based distribution generation. For this, a new benchmark model has been developed according to the European Network of Transmission System Operators (ENTSO-e) guidelines. A 400 kV transmission network has been modeled in detail by taking into account wind turbine (WT) Type-3, Type-4 and PV generation as well as conventional generation where applicable. The network also makes use of a point-to-point HVDC connection, and it can be used to simulate variable penetration of distribution generation up to 100%. The system is modeled in details by making use of EMT models developed in RTDS environment. Numerous tests have been performed for protective relays from different vendors and different grid code constraints. The performance of the different vendor distance relay is analyzed for different fault types on transmission line. Further, a transient-based hybrid scheme has been discussed that is capable of operating under challenging conditions. The work is realized in the frame of the large EU Horizon 2020 project MIGRATE to study the performance of power system protection with large penetration of power electronic devices.@en

Type 4 wind turbines are becoming one of the most employed technologies for all new wind turbines installed in the power system and their penetration is expected to increase. This technology presents the advantage that of fully decoupling the behavior of the generator from grid disturbances. This decoupling helps the wind turbine to reach the compliance requirements of international grid codes [1] during grid disturbances.Considering such circumstance, within Work Package 4 of EU funded MIGRATE Project, an ad-hoc Type 4 wind turbine model has been developed in Real-Time Digital Simulator (RTDS) platform, including algorithms for international grid code compliance and independent controls for positive and negative sequence current. The objective of developing such detailed RTDS model is to apply tests in laboratory to real protection relays, from different vendors, to study potential problems or limitations of present protection algorithms in the case of high penetration of this type of renewable energy generation sources into the grid. The in-depth analysis of the results obtained in such tests allows identifying specific weak points of the present protection algorithms in the considered scenarios, thus paving the way for the research on new protective solutions, as it is shown in the present paper.@en