Due to increasing levels of fault currents, fault current limiters (FCLs) are expected to play an important role in the protection of future power grids. Inductive saturable FCLs are particularly interesting due to their inherent reaction on the fault. Many different configurations have been proposed in literature. Being difficult or impossible to create accurate analytical models of some FCL configurations, the development of finite element (FE) models for inductive FCLs is required. This paper presents a 3D nonlinear transient FE modeling technique applied to two inductive FCLs, namely the so-called open-core and three-leg single-core FCLs. The models have been validated by comparing simulation results with lab measurements. Results show excellent agreement. The models constitute a valuable tool for design, optimization, and verification of inductive FCLs. @en

Fault current limiters (FCLs) are expected to play an important role in protection of future power grids. By inserting a limiting impedance in series with a line, they limit the increasing levels of the fault currents to acceptable values. Inductive FCLs based on core-saturation effect are particularly interesting due to their inherent reaction on a fault. However, some challenges are to be solved: too large amount of required material and induced over-voltage across the DC winding that is used to drive the core into saturation. This paper introduces a new configuration of the inductive FCLs, where the amount of the required material is reduced considerably and the induced over-voltage across the DC winding is decreased. The amount of magnetic material is reduced by employment of one core per-phase instead of two. The middle leg of the three-leg core is used as a shunt path for the AC flux. It enables a gap insertion in the AC magnetic circuit without influencing the DC magnetic circuit, i.e. the amount of DC winding material. Thus, a smaller core (less magnetic material) can be used for the same power level. Results obtained from the lab prototype match very well the one from simulations.@en

Fault current limiters (FCLs) are expected to play an important role in protection of future power systems. Saturated-core FCLs are particularly interesting because of their supreme operational advantages: inherent reaction on a fault, inherent post-fault recovery and unrestricted duration of a limiting period. The testing of a lab-scale FCL prototype proved the principle of operation. The full-scale 10 kV/400 A FCL prototype is built in co-operation with industry partners. The initial low-voltage 400 V testing has been successful. Full-voltage 10 kV testing will be performed later this year.@en

This paper presents a new component within the flexible ac-transmission system (FACTS) family, called distributed power-flow controller (DPFC). The DPFC is derived from the unified power-flow controller (UPFC). The DPFC can be considered as a UPFC with an eliminated common dc link. The active power exchange between the shunt and series converters, which is through the common dc link in the UPFC, is now through the transmission lines at the third-harmonic frequency. The DPFC employs the distributed FACTS (D-FACTS) concept, which is to use multiple small-size single-phase converters instead of the one large-size three-phase series converter in the UPFC. The large number of series converters provides redundancy, thereby increasing the system reliability. As the D-FACTS converters are single-phase and floating with respect to the ground, there is no high-voltage isolation required between the phases. Accordingly, the cost of the DPFC system is lower than the UPFC. The DPFC has the same control capability as the UPFC, which comprises the adjustment of the line impedance, the transmission angle, and the bus voltage. The principle and analysis of the DPFC are presented in this paper and the corresponding experimental results that are carried out on a scaled prototype are also shown.@en

The Distributed Power Flow Controller (DPFC) is a new device within the FACTS family. It is emerged from the UPFC and has relatively low cost and a high reliability. The DPFC consists of two types of converters that are in shunt and series connected to grids. The common dc link between the shunt and the series converters is eliminated. The active power exchange between the shunt and series converters that is through the common dc link in the UPFC, is now though the transmission line at the 3rd harmonic frequency. The redundancy of the series converters provides the high reliability of the system. In this paper, the DPFC behavior during the failure of a single series converter unit is considered. A control scheme to improve the DPFC performance during the failure is proposed. The principle of the control is based on the facts that, the failure of single series converter will lead to unsymmetrical current at the fundamental frequency. By controlling the negative and zero sequence current to zero, the failure of the series converter is compensated. In this paper, the principle of the DPFC are firstly introduced, and followed by the behavior of the DPFC during the failure of a single series converter. The design of the control scheme and corresponding simulation are presented.@en

Fault current limiters (FCLs) are expected to play an important role in the protection of future power grids. Inductive FCLs are particularly interesting due to their inherent reaction to a fault, but are not commercialized because of a too large amount of magnetic material and an induced overvoltage across dc windings. This paper introduces a new three-phase FCL with a common core and trifilar windings. With the new FCL topology, the phase windings are placed on a single core, resulting in significant reduction of the amount of required magnetic material. Furthermore, the phase windings are wound simultaneously, so that the flux coupling between the phases is increased considerably. It cancels out the magnetic field and reduces the FCL normal impedance significantly. The dc windings are used only to compensate for possible asymmetry in the system currents. Consequently, the number of dc turns and the induced overvoltage are considerably decreased. Testing of a scaled-down FCL lab prototype made it possible to verify the FE simulation results and demonstrated the principle of operation of the new topology. Experimental and simulation results matched very well.@en

Fault Current Limiters (FCLs) are expected to play an important role in protection of future power systems. FCLs can be classified in three groups: passive, solid-state and hybrid FCLs. Passive FCLs have merit to inherently react on a fault, requiring no fault detection and triggering circuit. Inductive FCLs based on core saturation belong to this group. Analytical models, used for design of inductive FCLs, are not accurate enough; BH curve cannot be expressed as an explicit function. Numerical models offer better approximations, but they often do not include effects such as leakage and fringing fluxes, which can have considerable influence on the result. Verification of such models is of utmost importance. Finite element modeling (FEM) tools offer possibility to model any inductive FCL topology, while all the effects, e.g. non-linear BH curve, fringing effects etc., are taken into account. However, the modeling of these devices in FEM softwares is difficult. This paper introduces the guidelines for development of 2D/3D transient FE models of inductive FCLs in Ansys. The guidelines are developed with respect to the single-core inductive FCL topology. The model can be applied to any inductive FCL and presents a valuable tool for design, verification and optimization of these devices. Signals' waveforms, obtained through the transient analysis, provide precise depiction of FCL operation during both normal and fault regimes. The model is validate by means of lab experiment. Simulation and experimental results show very good matching. In addition, modeling results are used to prove that single-core FCL topology operates properly during both nominal and fault regimes.@en

Abstract Installation of new generating units and increased penetration of distributed generators (DGs) in the power systems increase the total power transmitted in the power grid. In the case of a fault, the amount of power captured by a short circuit is enlarged, leading to higher peaks of the fault currents and, consequentially, to higher stresses to the power system components. Installations of fault current limiters (FCLs) are expected to prevent expensive upgrade and replacement of the components exposed to the over-stresses. Inductive FCL are particularly interesting due to their inherent reaction to a fault. However, some challenges are to be solved: excessive weight and induced over-voltage across the DC winding. The goal of this paper is to introduce a new configuration of the inductive FCL, where the amount of the required material has been reduced considerably and the induced over-voltage across the DC winding is decreased. Employment of one core per-phase instead of two reduces the amount of magnetic material. The core has three legs, where the middle leg is used as a shunt path for the AC flux. It enables a gap insertion in the AC magnetic circuit without influencing the DC magnetic circuit, i.e. amount of DC winding material. This means that a smaller core (less magnetic material) can be used for a same power level. The simulation results obtained from FCL models created in SaberDesigner are presented. They have been confirmed through the testing of the lab-scale prototype.@en

Fault current limiters (FCLs) are expected to play an important role in the protection of the future power networks, since the increase of loads and expansion of the power networks lead to much higher short-circuit power. This paper presents the comparison of four different configurations of inductive FCL, with respect to the FCL weight (magnetic core and winding material) and losses during both the nominal and the fault state of operation. Two main challenges in the inductive FCL design are reduction of the material weight and reduction of the induced dc winding over-voltage during the fault period. So far, solutions (core configurations) proposed in the literature are: decoupling of the dc and the ac magnetic circuits to avoid high voltages across the dc winding during a fault and the so-called open- core configuration. The presented results reveal the merits and drawbacks of each of the configurations and compare them to the conventional inductive FCL design characteristics. The results are obtained through the simulations in SaberDesinger and by experiments.@en

Fault current limiters (FCLs) are expected to play an important role in the protection of the future power networks, since the expanding of the power networks leads to much higher short-circuit power. This paper presents an analysis of the influence of different types of FCLs on the short-circuit energy dissipation and signal waveforms of the power line upon the fault occurrence. Dissipated energy upon the fault inception is determined for the resistive FCL considering two types: solid-state FCL and hybrid FCL. The reduction in the amount of energy imposed on a CB by employing a resistive or an inductive FCL is analyzed. The results of the analysis of the power system behavior upon the fault occurrence, from the aspect of energy dissipation in different components, are presented. Also, the dependency of the line current waveform on the moment of the fault inception and the FCL reaction time is shown.@en