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Abstract The escalating levels of fault currents resulting from short circuits, particularly in the context of distribution generators, have presented a critical need for the widespread implementation of fault current limiters (FCLs) in power systems. Despite their evident advantages, the extensive adoption of FCLs has been hindered by the high production costs associated with these devices. To address this challenge, a comprehensive study was conducted to develop a cost-effective FCL tailored specifically for three-phase power systems. This paper proposes a novel approach based on a single commutation circuit for the FCL and offers detailed insights into the construction of the FCL circuit, with a particular focus on efficient current interruption. Additionally, the study comprehensively discusses the logic controller and measurement system employed in conjunction with the proposed FCL, ensuring precise fault detection and rapid response to disturbances within the power grid. The integration of an artificial zero-crossing circuit within the FCL design further enhances its capability to limit short-circuit currents proactively, even before the occurrence of the first peak, thereby bolstering overall system reliability and stability. The study's significant contribution lies in achieving cost-effectiveness through the simplicity of the FCL's design, eliminating the need for extensive upgrades to various network components.

Abstract A new passive islanding detection technique based on transient energy that is measured and analysed at targeted distributed generation (DG) or the point of common coupling (PCC) is presented. The proposed technique measures the superimposed components and then calculates the transient active energy (TAE) and the transient reactive energy (TRE). Using the relation between TAE and the TRE, the relay can determine the islanding situation even in a worst‐case operational scenario, and this is a notably shorter response time according to the current standards. The performance of the proposed technique is simulated in the MATLAB environment. Islanding and non‐islanding scenarios for different power match conditions and types of DGs are simulated. The evaluation of the simulation results shows that the proposed technique identifies the islanding with a less than zero power mismatch, operates accurately under the condition of load variation, and does not conflict with the power system operation during normal conditions. It removes the passive technique drawbacks by having a tiny non‐detection zone (NDZ) and a faster response.

The paper presents an economic hybrid circuit breaker for limiting and interrupting the faults in DC railways substations. For fast fault current interruption, the hybrid breaker incorporates high speed mechanical contacts actuated by power semiconductor devices. Additionally, to avoid formation of electric arc, a commutation circuit is used to inject a counter current during fault interruption. In a real railway substation, each feeder is connected to the main DC bus through an expensive air magnetic DC circuit breaker and to an auxiliary DC bus through another expensive breaker. This leads to high cost especially in railway substation with multi feeders which are used to energize the vehicle transmission lines. In this paper, all DC breakers in DC railway substations are replaced by the suggested circuit breaker, which consists of a high speed mechanical contact with two semiconductor devices in each feeder and only one commutation circuit for injecting the counter current in all faulted feeders. The fault diagnosis is designed to detect the abnormal condition (current or voltage) in all feeders and direct the injected current from the commutation circuit to the faulted feeder only when the abnormal reaches a predetermine level. The suggested breaker is able to detect and interrupt any cascading of faults.

This paper describes the development of the hybrid fault current limiter and interrupting device (HCLID) which can be used successfully as a fast short-circuit protection means for low voltage AC industrial installations. The main components of the HCLID are a solid state commutation circuit that can supply a counter current injection from a stand-by pre-charged capacitor, saturable core reactor as the limiting impedance and fast mechanical contact switch all connected in parallel. Through this study, we can present a significantly improved and simplified approach that replaces the half-controllable silicon-controlled rectifier (SCR) in the commutation circuit with self-turn-off device such as integrated gate-commutated thyristor (IGCT). The use of high-performance semiconductors (IGCTs) as the commutating affords reduced recovery voltage, reduced losses, improved reliability and dynamic performance, and fast switching time (in μs). The new approach involves a fault detection using rate of current rise rather than the current magnitude and a time delay operating characteristic based on Piecewise Linear Electrical Circuit Simulation (PLECS) program. The control method is very simple. Simulations carried out during the research. Simulation results proved the practicability and validity of the new HCLID.