Line Current Differential Relays Research Articles

Cyber-Immune Line Current Differential Relays

Cyber-Immune Line Current Differential Relays

Enhancing grid protection: The crucial role of resistive-type superconducting fault current limiters in transmission line current differential relays

Superconducting fault current limiters (SFCLs) offer an efficient means of limiting fault currents and supporting system reliability. However, they weaken the fault characteristics and reduce the sensitivity of traditional relay protection. The seamless integration of SFCLs with protective relays remains a complex and under-explored area, impeding their widespread industrial adoption. In parallel, current differential protective (CDP) relays are almost the primary protection for all high-voltage electrical equipment and are the cornerstone of global power system security. This paper fills a critical knowledge gap by researching the intricate interaction between resistive superconducting fault current limiters (R-SFCLs) and current differential protective relays. Our investigation commences with a comprehensive mathematical analysis, while researching the influence of R-SFCLs on CDP operation. Subsequently, we conduct a series of comparative experiments using the Matlab Simulink software platform. These tests evaluate the sensitivity, dependability, and security of CDPs in scenarios with and without R-SFCLs. The simulation results not only confirm the accuracy of our analytical framework but also shed light on the multifaceted relationship between R-SFCLs and CDPs. This research contributes to a deeper understanding of how R-SFCLs can be effectively integrated into power systems, offering a roadmap for enhancing grid protection.

Cyber intrusion detection for line current differential relays in DC distribution system

Line current differential relays (LCDRs) are used as a promising solution for DC system protection. Such relays rely on communication channels (for remote end data) for decision and therefore, are susceptible to cyber intrusions. The false data injection (FDI) based cyber attack is one of the prominent threats, which may cause unintentional tripping of LCDRs. This paper presents a cyber intrusion detection algorithm based on the change in slope of the superimposed component of current in both ends of the line segment. The proposed algorithm distinguishes cyber attacks from the internal faults. The case studies are carried out on an IEEE 37 bus distribution system modified into a DC distribution test system in a real-time OPAL-RT environment. The performance of the proposed method is tested for different conditions including high resistance fault, FDI attack, load change, switching effect and signal with noise.

Anomaly-Based Detection of Cyberattacks on Line Current Differential Relays

Currently, the architecture of Line Current Differential Relays (LCDRs) is designed to respond to internal faults on the protected line using local and remotely-communicated current measurements. However, this architecture cannot distinguish between real faults and cyber-induced attacks whose goal is to cause false tripping of the line protected by the LCDR. In this paper, we propose an Anomaly-Based Scheme (ABS) for detecting false-tripping attacks against LCDRs, in the form of relay attacks, replay attacks, general false-data-injection attacks, and time-synchronization attacks. The ABS employs the Isolation Forest algorithm, which is trained on features determined from local current measurements to confirm real faults and differentiate them from false-tripping attacks. No trip command will be issued unless the sensed fault is confirmed as a non-attack by the ABS. The performance of the proposed ABS is tested and validated using the IEEE 9-bus benchmark in PSCAD/EMTDC environment. Simulation results show that the proposed ABS: (i) can accurately detect different categories of cyberattacks, (ii) does not negatively impact the accuracy of the fault-detection function, and (iii) is robust to the change in the power system’s operating point.

A Learning-Based Framework for Detecting Cyber-Attacks Against Line Current Differential Relays

Technical developments in communication technology and measurement synchronization have facilitated the design of advanced protection schemes, such as Line Current Differential Relays (LCDRs). However, the superior performance of LCDRs is achieved at the expense of exposing them to cyber-threats, since cyber-induced intrusions against protective relays-which take advantage of the direct control of relays over circuit-breakers-can cause protection system mis-operations. To address this problem, this paper presents a Learning-based Framework (LBF) for detecting False Data Injection Attacks (FDIAs) and Time Synchronization Attacks (TSAs) against LCDRs, and for differentiating them from faults. In the proposed LBF, a Multi-Layer Perceptron (MLP) model is trained based on differential and super-imposed features, which are selected using the Recursive Feature Elimination method. After implementing the proposed LBF in LCDRs, when an LCDR picks up, it initially extracts the features and sends them to the trained MLP model. The LCDR trips the line if the proposed LBF confirms a fault. The performance of the proposed LBF is corroborated using the IEEE 39-bus test system. Evaluation results show that the proposed LBF (i) works independently of a system's operating point and configuration, (ii) is not considerably affected by instrumentation errors, and (iii) can accurately detect FDIAs and TSAs.

STUDI SISTEM PROTEKSI LINE CURRENT DIFFERENTIAL RELAY PADA SALURAN TRANSMISI 150 KV

Increasing electricity demand in South Bali requires a reliable electrical system. Reliableelectrical systems can be achieved in various ways, one of which is the replacement of highvoltage overhead line to high voltage underground cable. The replacement high voltageoverhead line to high voltage underground cable requires adjustment of the protection system.The previous main protection system used in high voltage overhead line is distance relay, whilethe protection system for the new transmission network is line current differential relay. Thepurpose of this study is to analyze GIS Pesanggaran to GI Nusa Dua transmission line’sprotection system. The covered in this analysis is to power flow analysis simulation, 3 phaseshort circuit simulation, relays setting calculation and testing the relays setting.The power flowsimulation showed that the current at peak load from GIS Pesanggaran to GI Nusa Dua is 337A. The 3 phase short circuit simulation showed that the largest short circuit, if a fault occurs onthe GI Nusa Dua of 9.54 kA. The relays setting calcullation showed that of 0,2 A with 20 %slope for Is1 and 2 A with 150% slope for Is2. The results showed that the relays setting hasworked properly.

An Intrusion Detection Method for Line Current Differential Relays in Medium-Voltage DC Microgrids

Line current differential relays (LCDRs) detect faults accurately and promptly, by comparing all currents flowing into the line. This type of relay has been identified in the literature as a reliable protection for lines in DC microgrids (MGs). LCDRs, however, lack the required resiliency against cyber intrusions, such as false data injection attacks (FDIAs) and time synchronization attacks (TSAs), due to their high dependence on communication infrastructure and/or the Global Positioning System (GPS). This paper first introduces coordinated attacks—i.e., several almost-simultaneous FDIAs or TSAs that are carried out independently to achieve a specific objective—as potential threats for MGs. Then, through a case study, it shows how coordinated FDIAs and TSAs can initiate a sequence of events that result in instability of an entire MG. Afterwards, an approach is presented to detect FDIAs and TSAs, and to distinguish them from real faults. The proposed method is comprised of passive oscillator circuits (POCs) installed in series with each converter. During faults, the resultant RLC circuit causes the POCs to resonate and generate a damped sinusoidal component with a specific frequency, i.e., $f_{d}$ . However, $f_{d}$ is not generated during FDIAs and TSAs, since unlike faults, which are physical events that trigger the natural frequencies of a system, cyber-attacks happen in the cyber layer without provoking natural frequencies of the physical layer. Thus, an LCDR pickup without detecting $f_{d}$ denotes an FDIA or a TSA. Since $f_{d}$ is locally measured and analyzed by each LCDR, the proposed detection approach cannot be targeted by cyber-attacks. The proposed method is evaluated on a simulated ±2.5 kV DC MG. Numerical analysis confirms that the proposed method (i) is system-independent; (ii) detects FDIAs and TSAs in less than 1 ms; (iii) is sensitive to high-resistance faults; (iv) can determine fault types, and (v) reduces faults’ peak currents.

An Intrusion Detection Method for Line Current Differential Relays

The U.S. Department of Homeland Security (DHS) has recently identified digital relays as targets vulnerable to cyber-attacks. The DHS has also noted that attacks to multiple relays can bring about cascading outages of transmission lines, leading to blackouts. As a result, making protective relays cyber-resilient is a prominent security issue in power networks. Line current differential relays (LCDRs) are among the potentially vulnerable digital relays that are increasingly deployed for protecting critical transmission lines. LCDRs, however, lack the required resiliency against cyber attacks, due to their high dependence on communication systems. This paper unveils that such susceptibilities can result in unwarranted trip signals through false data injection attacks (FDIAs), and so cause instability if several attacks are coordinated. It also presents a solution for detecting FDIAs and distinguishing them from real internal faults. To detect attacks, the proposed method compares the estimated and locally measured voltages at an LCDR’s terminal for both the positive sequence (PS) and negative sequence (NS). To estimate the local voltage for each sequence, the proposed technique uses an unknown input observer (UIO), the state-space model of the faulty line, and remote and local measurements, all associated with that sequence. The difference between the measured and estimated local voltages for each sequence remains close to zero during real internal faults because, in this condition, the state-space model based on which the UIO operates correctly represents the line. Nevertheless, the state-space model mismatch during FDIAs leads to a large difference between measured and estimated values in both sequences. The effectiveness of the proposed method is corroborated using simulation results for the IEEE 39-bus network.

Development of a Cyber-Resilient Line Current Differential Relay

The application of line current differential relays (LCDRs) to protect transmission lines has recently proliferated. However, the reliance of LCDRs on digital communication channels has raised growing cyber-security concerns. This paper investigates the impacts of false data injection attacks (FDIAs) on the performance of LCDRs. It also develops coordinated attacks that involve multiple components, including LCDRs, and can cause false line tripping. Additionally, this paper proposes a technique for detecting FDIAs against LCDRs and differentiating them from actual faults in two-terminal lines. In this method, when an LCDR detects a fault, instead of immediately tripping the line, it calculates and measures the superimposed voltage at its local terminal, using the proposed positive-sequence (PS) and negative-sequence (NS) submodules. To calculate this voltage, the LCDR models the protected line in detail and replaces the rest of the system with a Thevenin equivalent that produces accurate responses at the line terminals. Afterwards, remote current measurement is utilized by the PS and NS submodules to compute each sequence's superimposed voltage. A difference between the calculated and the measured superimposed voltages in any sequence reveals that the remote current measurements are not authentic. Thus, the LCDR's trip command is blocked. The effectiveness of the proposed method is corroborated using simulation results for the IEEE 39-bus test system. The performance of the proposed method is also tested using an OPAL real-time simulator.