A Study on a Communication-Based Algorithm to Improve Protection Coordination under High-Impedance Fault in Networked Distribution Systems

In recent years, the networked distribution system (NDS), which is normally connected to the distribution line (DL), was actively studied as the topology of the future distribution system for reasons such as improving supply reliability, improving line utilization, and increasing the capacity of distribution generators (DGs). However, the NDS creates new issues in terms of protection coordination because of its bidirectional power flow and fault current flow. The issues associated with conventional protection schemes in the NDS include malfunction of protective devices due to bi-directional fault currents and failure of protection coordination due to communication failures between protective devices. When applying a conventional protection method in the NDS, the protection schemes become complicated, and there is a risk of protection coordination failure due to communication failure between protective devices. To solve this problem, this paper proposes an effective and innovative non-communication-based protection algorithm for protection coordination in the NDS. The proposed protection algorithm utilizes fault impedance characteristics, which allow not only determination of whether a fault occurred, but also the ability to identify the exact fault point. Therefore, the proposed method is expected to be sustainably utilized and contribute to developing protection schemes and devices in various system topologies and scenarios in the future. Additionally, this paper addresses the overall concept of hardware-in-the-loop simulation (HILS) and directly verifies the proposed protection algorithm using HILS. Therefore, this study establishes a sustainable foundation for future research on protection coordination using HILS.

High‐impedance faults (HIFs) in electrical power distribution systems produce a very random, non‐linear and low‐magnitude fault current. The conventional overcurrent (OC) relaying‐based distribution system protection schemes find difficulty in detecting such low‐current HIFs. In this study, a simple two criteria‐based protection scheme is proposed for detection and isolation of HIFs in multi‐feeder radial distribution systems. It utilises one‐cycle sum of superimposed components of residual voltage for HIF detection and the maximum value of one‐cycle sum of superimposed components of negative‐sequence current for faulted feeder identification. The performance of the proposed scheme is evaluated for a wide variety of possible test cases by generating data through power systems computer‐aided design/electro‐magnetic transient design and control software. Results clearly show that the proposed scheme can assist conventional OC relay for detection and isolation of HIFs in distribution systems with any grounding connections in a more reliable and faster way.

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>

High impedance fault (HIF) is hard to detect owing to their relatively small magnitude compared to normal currents. When an overhead power line loses its support, fall on a poor conductive surface or substance, a high Impedance Fault results. As the fault current is very small during it becomes very difficult to be sensed by over current relay. So equipment and public safety become a matter of great concern. Due to its relatively small fault current nature it became an area of interest and need more detailed study to detect the HIF fast. Here, we try to present a new detection method which uses residual power as an input in the paper. The method is very simple and easy to implement compared to other heuristic methods. The proposed method is tested on eight bus system with DG connected at bus 4. The system is operating at 11kV voltage. The model is simulated in PS CAD. Capacitor switching, Generator switching, Unbalanced load condition, fault with and without DG are also simulated. Obtained results show that the method is able to detect High Impedance Fault with the inception of non-fault events also.

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.

A two-level ANN-based method using synchronized measurements to locate high-impedance fault in distribution systems

The fault current has increased due to the large power demand in power distribution system and network distribution system. To protect the power system effectively from the increased fault current, the superconducting fault current limiter (SFCL) has been notified. However, the conventional SFCL has some problems such as cost, operation, recovery, loss. To solve some problems, the hybrid superconducting fault current limiter using the fast switch was proposed. However, hybrid SFCL also has a problem that is protection coordination in power distribution system with hybrid SFCL. In this paper, the fault current limiting characteristics of hybrid SFCL with first half cycle non-limiting operation according to the fault angle, the resistance of superconducting element, and the magnitude of Current Limit Resistor (CLR) which are the components of hybrid SFCL were analyzed through the experiments.

As one of the countermeasures to solve the increase problem of the fault current in a power system, the superconducting fault current limiter (SFCL) has been noticed as the attractive device because it has no power loss in a normal time and can limit the fault current rapidly without additional device to detect the fault current. However, the introduction of the SFCL in a power distribution system affects the protection coordination between the existing protective devices such as the over-current relay (OCR) and the recloser, which causes the operation of the protective devices to get out of their original setting values. Therefore, the analysis on the effect of the SFCL introduction on the existing protective devices is required and the method to keep the protection coordination between the protective devices in a power system with the SFCL should be first considered. In this paper, the protection coordination experiments between the OCR and the recloser in the simulated power distribution system with the SFCL were performed. Based on the experimental results, the influence of the SFCL on the operation of these protective devices was analysed and the methods to keep the protection coordination between the OCR and the recloser in a power distribution system with the SFCL were discussed.

This paper presents an artificial neural network (ANN) and support vector machine (SVM) approach for locating faults in radial distribution systems. Different from the traditional Fault Section Estimation methods, the proposed approach uses measurements available at the substation, circuit breaker and relay statuses. The data is analyzed using the principal component analysis (PCA) technique and the faults are classified according to the reactances of their path using a combination of support vector classifiers (SVCs) and feedforward neural networks (FFNNs). A practical 52 bus distribution system with loads is considered for studies, and the results presented show that the proposed approach of fault location gives accurate results in terms of the estimated fault location. Practical situations in distribution systems, such as protective devices placed only at the substation, all types of faults, and a wide range of varying short circuit levels, are considered for studies. The results demonstrate the feasibility of applying the proposed method in practical distribution system fault diagnosis.

An increasing number of fire and electric shock accidents in power sector increases the need for high impedance fault (HIF) detection as the existing over-current relay in the system is not able to detect the HIF state. The HIF detector employing sequence components of current along with voltage is proposed in this paper. The proposed HIF detector composed of two components i.e. current HIF detector and voltage HIF detector, in conjunction with existing distribution network set up. The first component analyzes current sequence components when fault appears in the network whereas later analyzes voltage sequence components. The current HIF detector operates when, significant amount of zero and negative sequence components starts appearing in the network. On the other hand, voltage HIF detector assists the current HIF detector in confirming the HIF state by examining the negative voltage sequence component. The performance of combined detector is evaluated by inducing high impedance fault at different nodes on the IEEE-6-bus radial balanced distribution system. The proposed detector makes use of only current and voltage of the system for HIF detection and doesn't require any additional feature extraction phase. The HIF detector in the proposed paper requires only one unit of sequence converter. Now, sequence components coming out from sequence converter are fed to HIF relay logic which is used in conjunction with existing over-current relay. Hence, this detector is cost effective as compared with the different HIF detectors presented in literature. The proposed method is simulated in a simulation environment. This method is fast and reliable as it detects the fault within one cycle.

Due to the concerns for reduction of system losses, providing back-up power during loss of the grid, mitigation of energy security risks and conspicuous perturbation of power outages triggered by severe environmental constraints; the modernized distribution grids elicited grid resiliency and reliability enhancement through pragmatic enforcement of the Microgrid (MG) concept with distributed generation. With the proliferating power ultimatum, several intricate factors prone to MG operation modes, bidirectional power flow complexities, management and control of power transfer, varying fault current contribution, and high impedance faults (HIF) customized the network configuration and imperiled the protection system operation and system stability. The propitious utility framework persuaded the prerequisites to embrace the integration of state-of-the-art affiliated Distributed Energy Resources (DERs), which requires assimilated and coordinated studies to emphasize the outcomes of an efficient, reliable, and fast protection scheme for both the grid-connected and islanded modes of operation. Operating modes of distributed generation (DG) will affect the magnitude and direction of fault currents resulting in failure of protection coordination between directional overcurrent relays (DOCRs). In this paper, the negative-sequence based adaptive directional overcurrent relay (NSADOCR) stratagem is proposed. Protection coordination is accomplished by a new adaptive approach, which alters time dial setting (TDS) of negative-sequence overcurrent relay based on the ratio of the normal mode to operating mode of plug setting multiplier function. Furthermore, the direction of fault is attained using phase change in between the pre-fault and superimposed negative-sequence current components. Performance of the NSADOCR is evaluated on the dSPACE controller board, which is interfaced with Real- Time Digital Simulator (RTDSTM) to perform the hardware-in-the-loop (HIL) tests. Extensive simulation studies and hardware results on DG systems exemplify and indicate that the new adaptive technique results in effective protection coordination over the conventional approach, considering various distribution network (DN) modes of operation.

A rule-based expert system designed to locate the faults in a distribution system is presented. Distribution system component data and network topology are stored in the database. A set of heuristic rules is compiled from the dispatcher's experience and imbedded in the rule base. To locate distribution system faults, an inference engine is developed to perform deductive reasoning on the rules in the knowledge base. The inference engine comprises three major parts: the dynamic searching method, the backtracking approach, and the set intersection operation. The expert system is implemented on a personal computer using the artificial intelligence language Prolog. To demonstrate the effectiveness of the proposed approach, the expert system has been used to locate faults in a real underground distribution system within the service area of the Taipei City District Office of the Taiwan Power Company. It is found that the expert system can identify fault location very efficiently. Therefore, it can serve as a valuable tool to help distribution system dispatchers determine fault locations.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

High impedance faults (HIFs) are easy to occur in collective feeders in wind farms and may cause the cascading of wind generators tripping. This kind of faults is difficult to be detected by traditional relay or fuse due to the limited fault current values and the situation is worse in wind farms. The mostly adopted HIF detection algorithms are based on the 3rd harmonic characteristic of the fault zero-sequence currents, whereas these 3rd harmonics are very easy to be polluted by wind power back-to-back converters. To solve this problem, the typical HIF arc flash based on Mayr's arc model is first built, and the typical fault waveforms of HIF in wind farm are presented. Then the characteristics of high impedance faults are analysed to distinguish the occurrence of HIF from other harmonic interference. After that, the performance of the traditional harmonic based HIF detection algorithm is discussed, and a novel detection algorithm is presented to prevent harmonic interference influence in wind farms.

The circuit breakers, reclosers, and fuses are the main protective devices in the power distribution systems. However, due to the high penetration of wind generators in the existing distribution systems, the protective devices are exposed to high current levels, which may deteriorate the protection coordination performance and even can cause major blackouts in the distribution systems. This paper proposes the Sliding Mode Controller (SMC) based bridge type fault current limiter (BFCL) for the protection coordination of the protective devices in the distribution network. The protection coordination operation is investigated through some case studies of the Memphis Light, Gas and Water (MLGW) division's distribution test feeder with the presence of a wind farm. The performance of the proposed SMC has been compared with that of the fuzzy logic controlled (FLC) BFCL. Extensive simulations have been performed by using the Matlab/Simulink software. Simulation results for different fault situations in the test feeder indicate that the proposed SMC can maintain the protective relay coordination well and the performance of the proposed SMC based BFCL is better than that of the FLC based BFCL.

High impedance faults (HIFs) are difficult to detect due to the low magnitudes of the associated fault currents, which can be comparable to current levels in steady state operation. When a conductor of a distribution system breaks and falls over on a surface with high electrical resistance, a HIF occurs as well as the formation of an electric arc. Since current levels during HIFs are low, conventional overcurrent protection is not suitable for fault detection, which may represent a risk to people’s safety and to distribution system assets. In this paper, a HIF detection method is developed for Smart Distribution Grids based on the Discrete Wavelet Transform (DWT). The proposed method utilizes the Multiresolution Signal Decomposition (MSD) to decompose current signals in DWT coefficients. The technique is used to identify specific high frequency content in the faulted phase current, caused by the presence of the electric arc during the HIF. Based on the analysis of the DWT coefficients behavior during the fault, a HIF detection algorithm is developed according to a certain indicators. The proposed method is tested on the IEEE 13 Node Test Feeder, which is simulated using the software PSCAD/EMTP.