Increasing penetration of inverter-based resources (IBRs) undermines the performance of conventional protection systems since IBRs’ fault characteristics are fundamentally different from those of synchronous generators. In this paper, a PMU-based backup protection method is proposed for power transmission systems with high penetrations of IBRs. The method involves replacing all IBRs and the line suspected to be faulty by proper nodal current sources. For accurately detecting the faulted line from the set of candidates, a residual-based index is proposed, utilizing the concept of superimposed circuits and the weighted least-squares method. The method's robustness in the face of influential factors, including input errors, settings, numbers, and locations of IBRs is investigated through extensive simulations on the IEEE 39-bus test system.@en

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

The conventional Under Frequency Load Shedding (UFLS) scheme could result in unacceptably low frequency nadirs or overshedding in power systems with volatile inertia. This paper proposes a novel UFLS scheme for modern power systems whose inertia may vary in a wide range due to high penetration of renewable energy sources (RESs). The proposed scheme estimates the rate of change of frequency (RoCoF) of the center of inertia (CoI), and consequently, the loss of generation (LoG) size, using local frequency measurements only. An innovative inflection point detector technique is presented to remove the effect of local frequency oscillations. This enables fast and accurate LoG size calculation, thereby more effective load shedding. The proposed UFLS scheme also accounts for the effect of the inertia change resulting from LoG events. The performance of the proposed scheme is validated by conducting extensive dynamic simulations on the IEEE 39-bus test system using Real Time Digital Simulator (RTDS). Simulation results confirm that the proposed UFLS scheme outperforms the conventional UFLS scheme in terms of both arresting frequency deviations and the amount of load shed.@en

Fault currents may result in cascading failures and even system collapse if not detected and cleared on time. To account for the possibility of failure of primary protection under stressed system conditions, an extra layer of protection is commonly employed, referred to as backup protection. This paper introduces an effective formulation for realizing remote backup protection using available data from PMUs and Intelligent Electronic Devices (IEDs). The proposed method is split into three main stages. The first stage deals with the zoning detection of the fault. The second stage is aimed at faulted line detection, and finally, the third stage determines the fault distance on the faulted line. The method is designed to take full advantage of measurements provided by PMUs and IEDs. The challenges associated with different reporting rates are resolved thanks to the dynamic decimator employed to this end. The proposed method has been implemented in real-time by applying co-simulation with MATLAB and validated using the New England IEEE 39 bus system with several fault events.@en

Short-circuit faults occurring close to either end of a transmission line are normally cleared with some time delay by the distance relay at the opposite end of that line. The pilot relaying schemes require communication media in order to reduce this time delay. This paper presents a noncommunication method that provides high-speed distance relaying over the entire length of transmission lines. Similar to conventional distance relays, the proposed method requires voltage and current signals at the relay location as well as the impedance parameters of the protected line as input. Accelerated sequential tripping (AST) for faults on the end-sections of the line is achieved by using the signals measured from the fault inception to several cycles after the opening of the remote-end circuit breaker (ORCB). A formula is put forward for determining the exact fault distance by using post-ORCB signals. Two indices are also proposed for detecting three-and single-pole ORCB in order to fulfill the prerequisite for accurate fault location and generating a trip command, if needed. The proposed method is validated by conducting more than 10000 simulations on the 39-bus test system using DIgSILENT PowerFactory.@en

Local protection elements such as fuses and relays are the first protective mechanism to clear the fault and isolate the affected part of the power grid. Although the selectivity, speed, and sensitivity of these primary protection devices are relatively high, they cannot be considered flawless. There is a small percentage of events for which relays experience blinding effects. For these scenarios, a redundant arrangement can be made through backup protection. This paper proposes a centralized remote backup protection method based on two techniques, the delta algorithm and the least-squares technique. The proposed method successfully detects the faulted transmission line, fault type, and the distance to the fault. Besides, it makes use of phasor measurement unit data and it is non-iterative. The grid is split in a user-determined number of subareas based on the phasor mesurement unit locations, in order to accurately determine the fault location. Firstly, the faulty area is located and thereafter an in-depth search is carried out on the faulted area to determine the faulted line. Finally, the fault distance is determined based on the distributed parameter model of the transmission line. The method is demonstrated and validated in an RTDS-Matlab co-simulation platform. Extensive simulation studies are carried out on the IEEE 39-bus system to validate the proposed method.@en

Short-circuit faults close to either end of a transmission line, are normally cleared instantaneously by the distance relay at that end and after hundreds of milliseconds, i.e., in Zone 2 operating time, by the relay at the opposite end of the line. This sequential tripping can be accelerated on condition that a reliable communication link is available for signaling between the two line ends. This paper proposes a novel non-communication method providing high-speed distance relaying over the entire length of the protected transmission line. The inputs to the method are the protected line parameters and local voltage and current signals measured by the relay, similar to those to conventional distance relays. The proposed method accomplishes Accelerated Sequential Tripping (AST) within a couple of cycles after the opening of the remote-end circuit breaker (ORCB) of the line. To achieve this, an accurate closed-form solution is derived for the fault distance in terms of post-ORCB voltage and current phasors. For the detection of the ORCB instant, a set of proper indices are proposed. This is to verify the fault distance calculated by the relay, before issuing a trip command. The proposed method is successfully validated by conducting more than 20000 hardware-in-the-loop (HIL) tests, and also using real-life data.@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