Advanced Algorithm for Fault Detection and Localization in DC Microgrids Utilizing Capacitor Current Transient Analysis for Enhanced Reliability in DER-Integrated Systems

Traditional fault detection and location schemes become ineffective for detecting and locating the fault in DC microgrid systems due to integrating various types of power electronic-based DC loads and generators. To resolve this issue, advanced, intelligent, specialized fault detection and location schemes are necessary. This article suggests a novel fault detection scheme based on the difference in the teager energy available in the DC current wave at sending and receiving ends of lines. After the detection of the fault, the location is calculated by estimating the resistance of the cable up to the fault point as well as the total resistance of the cable, with the help of least square technique. The proposed scheme decides fault is internal if the estimated fault location is less than 1 p.u. Otherwise, the proposed scheme decides fault is external. A DC microgrid with different types of generating units and loads is simulated using MATLAB/SIMULINK to evaluate the developed algorithm. Internal and external faults, pole-to-ground and pole-to-pole faults with changing fault resistance and fault location are some of the fault scenarios that have been simulated. The obtained simulation results prove that the suggested algorithm can discriminate between internal and external faults and locate the fault. The proposed technique is also examined on a DC microgrid hardware testbed and results show the efficiency of the suggested approach.

Nowadays, DC microgrid is getting much more attention due to its simplicity and cost-effective behavior. On the other hand, DC microgrid is facing protection issues due to lack of effective protection schemes. Therefore, protection has become a more crucial aspect in DC microgrid. In DC Microgrid, there are two types of fault, one is low impedance fault (LIF) and the latter one is high impedance fault (HIF). In this article, a high impedance fault has detected by using the Least Square estimation technique. And also, the fault location and fault resistance have been estimated. For the fault analysis, a five bus ring-type DC microgrid has been considered, and it has simulated using MATLAB/Simulink environment. The novelty of the proposed protection scheme is that it does not require any communication link to detect the fault.

A new fault detection and relay coordination technique for low voltage DC microgrid

Fault detection and location in multi-terminal DC microgrid based on local measurement

Accurate estimation of fault location is highly crucial for swift maintenance and early power restoration. Since faults in dc networks are time critical, this article proposes a new fault detection and localization scheme for a low-voltage direct current (LVdc) microgrid network. Low-resistance faults are detected by observing voltage across the inductor whereas high-resistance ground faults are identified by measuring ground current at the relay location. Thereafter, based on iterative method, fault location is estimated by comparing analytically derived fault current with the measured value of fault current. Genuineness of the suggested technique has been assessed by simulating various internal, external, and simultaneous faults on a typical LVdc microgrid network modeled in power system computer aided design/electromagnetic transients including dc (PSCAD/EMTDC) environment. The proposed method is capable of detecting and locating both low- and high-resistance dc faults without utilizing remote-end quantities. Subsequently, initial guess has minimal impact on the convergence and accuracy of the proposed algorithm. Comparative evaluation of the proposed technique with other techniques clearly proves its superiority in terms of better discrimination against external faults, rapid detection during internal faults, independency on the network topology, and higher accuracy for fault distance estimation against all types of internal faults.

To achieve the goal of zero emission in aviation, it is critical to advance electric aircraft technologies, especially in short to medium range flights. Superconducting fault current limiters (SFCLs) have shown promising potential in electric aircraft system as a protection solution to limit the peak of fault current. Many research works focused on the SFCL performance under low impedance faults, where the fault current is much higher than the nominal current and the SFCL will transit to normal (metal) state quickly. However, there are limited reports on investigating the SFCL reacting to high impedance faults for electric aircraft system, where the SFCL does not abruptly transit to normal state. In this paper, we built an electric-thermal coupled model in MATLAB which simulates the behaviour of a resistive type SFCL both under low and high impedance faults. We investigated three mathematical relations of local electric field E and local current density J representing the transition from superconducting state to normal state, both under high and low impedance fault. The three mathematical relations are classic E-J power-law, modified E-J power-law and two- stage E-J power law. The electric-thermal model of the SFCL incorporating all these three types of mathematical relations, respectively, have been used to calculate the SFCL responses under high and low impedance faults, and compared with each other, as well as testing results. The limited fault current, voltage drop, resistance and temperature variations in the SFCL are observed and analysed. The results have shown that the proposed SFCL model is able to accurately characterise a resistive type SFCL under both high impedance and low impedance fault.

In this paper it is proposed a novel high impedance fault detection and location scheme for power distribution feeders with distributed generation. The proposed scheme is capable to obtain precise fault location estimations for both linear low impedance and non-linear high impedance faults. This last class of faults represents an important subject for the power distribution utilities because they can be difficult to detect and locate by the protection devices commonly used in todays electric distribution systems. The proposed scheme uses real time data which are processed in a way that the fault detection and location can be estimated by a set of characteristics extracted from the voltage and current signals measured at the substation. This characteristic set is classified by an artificial neural network based scheme whose output results in a fault detection and location. The scheme is based on the calculation of the symmetrical components of the current signal harmonies at the relay point. Other traditional fault detection and location methodologies were also implemented, making possible to obtain comparative results. The scheme was applied in two simulated feeders. The results of this work shows, that the proposed methodology is worthy of continued research objecting real time applications.

The high penetration of renewable energy resources (RERs) increases the fault current level of direct current (DC) microgrids and causes bidirectional flow for fault current. Therefore, it may cause a miscoordination between fuses or other protection devices. The traditional coordination methods are based on shifting the operation curve of protection devices below the characteristic curve of the fuses during temporary faults to save fuses. However, in case of low variations of the system topology and low impedance faults, these methods can be used to save fuses. Also, in the case of high penetration of RERs, due to the variations of the short circuit level, the traditional methods are not effective. On the other hand, due to the lack of standards and proper protection methods in the DC microgrids, presenting a recloser switch - fuse coordination scheme for DC microgrids is essential. To address these issues, this paper proposes a fuse saving method by finding the appropriate setting of fuses and the recloser switch, which is effective for DC microgrids with various types and penetration levels of RERs. The proposed protection method is localized, and without communication links, it is applicable for both digital and conventional protection devices installed in the DC microgrids. The proposed scheme formulates the fuse-recloser switch coordination challenge as a curve-fitting problem and solves this problem to obtain the settings of the digital recloser switch and fuse. The proposed strategy provides a robust setting for fuse and digital recloser switch by considering different topologies of the DC microgrids. The proposed method is applied to a DC microgrid in different scenarios. The effectiveness and robustness of the proposed method are illustrated by digital time-domain simulation studies in the MATLAB/Simulink software environment and comparisons with previously-reported protection strategies.

The increased penetration of distributed generation resources (DGRs) in the distribution network, to fulfil the increased load demand, has changed the radial power flow nature of existing network in fault conditions. This results in mal-operation of the conventional protection devices. Thus, the existing methods fail to provide reliable protection for modified distribution system consisting DGRs. Moreover, detection of high impedance faults (HIFs) is also very important in such networks. Since, HIFs have very less fault current magnitude with nonlinear nature, it is difficult to detect them using conventional methods. Thus, a novel technique has been proposed in this paper for the fault detection and classification of distribution network under faults (i.e., lower impedance faults (LIFs) or high impedance faults (HIFs)). The fault detection and classification index is calculated in the proposed technique, using the energy obtained from the differential superimposed component of the positive sequence impedance. The proposed method effectively discriminates the internal and external faults, low impedance faults (LIFs), HIFs, switching transients and it distinguishes them as well. The IEEE-13 bus distribution system integrated with DGRs is used for simulation using Real Time Digital Simulator (RTDS).

High impedance fault detection method for distribution networks under non-linear conditions

The availability of distribution generations (DGs) in DC Microgrid causes the bidirectional current flow, it makes the fault detection process in the DC microgrid more complicated. Some of the available fault detection techniques are in the DC microgrid are fill to detect the fault during high resistance fault. This paper proposes a novel unit fault detection algorithm based on the line losses available each in the DC microgrid. The losses in each line segment are calculated by differentiating the sending and receiving, and power available at the line ends. The deference of power is compared with the I2 R losses of the line. During the fault losses are high due to the fault resistance and reveres flow of current. The proposed authenticity has been validated by simulating the various fault scenarios like external and internal faults using a typical LVDC microgrid system is design in the MATLAB platform. From the results obtained by the proposed method, it accurately detects the fault within a few microseconds.

Integrating distributed generation resources (DGRs) in the distribution system, forming microgrids or multi-microgrids (MMGs), has fulfilled the continuous rise in load demand over the past decade. However, the deeper infiltration of microgrids or MMGs in the distribution system provides an uninterruptable power supply and enhances the system's reliability. But their integration changes the system's fault current characteristics, radial nature, and fault current contribution levels. Thus, due to the abovementioned issues, the mal-operation of conventional relays may occur using the existing methods under fault conditions. Moreover, identifying low and high impedance faults is equally essential in active distribution networks (ADNs). Thus, this paper proposes a novel fault detection index for identifying low and high impedance faults. Further, a fault classification index is also proposed for classifying low and high impedance faults. The energy associated with the differential value of the superimposed component of the positive sequence impedance is utilized for the proposed technique. It also accurately discriminates the internal and external faults, switching transients, and non-linear loading conditions. The efficacy of the proposed method is further evaluated in the presence of noise components, and by considering the communication delay from one end. A modified IEEE-13 bus distribution system consisting both single DGR unit and multi-microgrids are considered for simulating these test cases. The simulation is performed using Real Time Digital Simulator (RTDS). The experimental setup is used to validate the proposed method for real-time scenarios.

An integrated high impedance fault (HIF) and low impedance fault (LIF) detection method is proposed in his paper. For a HIF detection, the proposed technique is based on a number of characteristics of the HIF current. These characteristics are: fault current magnitude; magnitude of the 3rd harmonic current; magnitude of the 5th harmonic current; the angle of the third harmonic current; the angle difference between the third harmonics current and the fundamental voltage; and the negative sequence current of HIF. These characteristics are identified by modeling the distribution feeders in EMTP. Apart from these characteristics, the above ambient (average) negative sequence current is also considered. An adjustable block out region around the average load current is provided. The average load current is calculated at every 18000 cycles (5 minutes) interval. This adaptive feature will not only make the proposed scheme more sensitive to low fault current, but it will also prevent the relay from tripping during the normal load current. In this paper, the logic circuit required for implementing the proposed HIF detection method is also included. With minimal modifications, the logic developed for the HIF detection can be applied to low impedance fault detection. A complete logic circuit which detects both the HIF and LIF is proposed. Using this combined logic, the need of installing separate devices for HIF and LIF detection can be eliminated.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

This study proposes a new differential relay characteristic to detect internal faults on bipolar HVDC (high voltage direct current) transmission lines and discriminate accurately and in a timely manner both internal and external faults. In comparison with the conventional differential protection characteristic, the proposed relay characteristic avoids the need for an intentional time delay typically required to avoid nuisance fault detection. The sampling currents of the positive and negative poles are obtained from both line ends, and the noise is eliminated from the current signals using a stationary wavelet transform. Initially, a startup unit is utilised to activate the proposed protection scheme. The proposed current differential scheme adopts a biasing technique, which is based on the inherent transient behaviour of the bipolar HVDC system during both external and internal faults. The HVDC transmission line is implemented on the PSCAD/EMTDC platform utilising the frequency‐dependent phase model, and it is tested considering numerous internal and external faults. Finally, the proposed current differential relay characteristic is tested considering different fault resistances up to 1000 Ω as well as different fault locations, including internal HVDC line faults and external faults at both rectifier and inverter sides. The obtained results confirm the robustness of the proposed protection scheme for bipolar HVDC transmission lines fault detection.

Advanced fault detection methodologies and communication protocols for DC micro grid -A technical review