Abstract — The settings and the protection functions of the relays are established by the TSOs based on networks with only synchronous generation or with power electronic devices with low level of penetration. In the recent years, the integration of renewable generators through partial or full-scale power electronics has been considerably increased. Renewable generators, depending on the demand are capable of fast switching so that their output current can be controlled during a load change in the grid. Although power electronic devices show good performance in terms of power support, the control strategy and its electrical architecture highly influence short-circuit current characteristic during faults. The waveforms of the fault currents with renewable generators differ significantly from those with conventional synchronous generators. During unbalanced faults, the reliability and the dependability of the relay may significantly decrease. In this paper, the performance of classical protection functions of two commercial relays (denoted as A and B) are investigated. The relays are tested in a Hardware-In-the-Loop environment and the strengths and weaknesses of these functions are determined. The results shown in this paper can be used as an overview of the actual protection device performances for different scenarios. Index Terms—Directional protection, Distance protection, Line differential protection, Renewable generators. I. INTRODUCTION ONVENTIONAL protection functions have been very reliable during years and even today play a major role for fault detection and identification. Current microprocessor based relays are able to operate by combining two or more protection functions like differential, distance, overcurrent etc. For traditional grids composed of synchronous generators (SGs), actual protection devices perform with very high level of reliability [1]. Nevertheless, we cannot say that they will show the same level of performance in future power systems with high renewable generator (RWG) penetration. It is well known that the existing grids are undergoing major changes with the inclusion of RWGs. In fact, according to REN21 [2] in 2017, 24.5% of the total power energy “This project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 691800” J.J. Chavez, M. Popov, and A. Novikov are with Delft University of Technology, Delft, 2628CD the Netherland (e-mail: j.j.chavezmuro@tudelft.nl; M.Popov@tudelft.nl). S. Azizi is with the School of Electronic & Electrical Engineering, University of Leeds, LS2 9JT, UK (e-mail: S.Azizi@leeds.ac.uk) V. Terzija is with School of Electrical and Electronic Engineering, The University of Manchester, Manchester, M13 9PL, U.K. (e-mail; vladimir.terzija@manchester.ac.uk). Paper submitted to the International Conference on Power Systems Transients (IPST2019) in Perpignan, France June 17-20, 2019. produced around the world was renewable with 16.6% resulting from hydropower plants and 7.9% from converter- based distribution generators. The power electronics (PE)- based RWGs were used as disperse generation in distribution systems and recently, the energy produced by renewables has been significantly increased. It is expected that the penetration level of the distribution generation in the years to come will further increase. The large scale of PE converters may sustain the stability of the power grid but may jeopardize the operation of the protective relays. Some problems with classical functions in actual grids were firstly reported in [3]. These are problems such as protective device coordination due to infeed and bi- directional current flow, synchronizing and autoreclosing as well as issues related to ground fault detection when distributed resources are connected to the grid. In [4], the wind power variation related to distance protection was studied. Voltage and current frequency discrepancy for a transmission line (TL) next to wind farm, which affects severely the performance of distance protection relays was analyzed in [5]. The effect of fault current frequency of a doubly fed induction generator (DFIG) that jeopardizes the operation of distance protection was reported in [6]. A distance relay failures near a Type-4 wind farm and possible solutions were discussed in [7] and [8] respectively. The performance of the distance protection in bulk wind generator systems was investigated in [9], [10] and ground fault protection issues were discussed in [11]. This paper reports the performance of actual protection relays applied in existing and forthcoming scenarios with high penetration of PE. In this context, the protection functions of differential, distance and directional protection for 2 different vendor relays are tested by applying real time Hardware-in-the- Loop (HiL) tests. The benchmark system is developed in an Electromagnetic transient based real-time simulator in a way to easily change the conditions of the grid. Nearly 5,000 simulation cases were performed following the recommendations provided in IEC 60255-121:2014 standard [12]. The results are well documented and classified. II. POWER SYSTEM DESCRIPTION AND HIL TEST PLATFORM Classical protection functions are tested in a HiL system as summarized in Fig. 1. The power system is developed in RTDS/RSCAD environment in a way to easily change its configuration and combine RWG and/or SG (see Fig. 2). Overall the simulation is performed with a 50μs time step. Protection Function Assessment of Present Relays For Wind Generator Applications Jose J. Chavez, Marjan Popov, Alexander Novikov, Sadegh Azizi and Vladimir Terzija C