Non-adaptive over current relay coordination in distribution systems

Increasing penetration level of distributed power generation in distribution system causes failure of existing non-directional and directional overcurrent relay coordination. A hybrid protection schemes based on application of fault current limiter and microprocessor based overcurrent relays is advised to eliminate the impact of distributed generation on distribution system relay coordination. The covariance matrix adaptation evolution strategy directed target to best perturbation based algorithm is applied for optimizing the setting of overcurrent relays. The performance the proposed algorithm is quite satisfactory as compared to other heuristic and met- heuristic based optimization algorithm. The proposed protection scheme requires minimum number of relay replacement and small size fault current limiter to mitigate the impact of distributed generation impact in the distribution system. The proposed protection scheme is simulated in MATLAB and tested on IEEE 30 bus distribution system.

Extremely penetration of Renewable Energy Sources (RES) into modern power systems inflicts many challenges when it comes to achieve optimal performance out of overall system. One of the potential issues is that RES are electromagnetically de-couple from the rest of the system as they are interfaced through power electronics with the traditional grid, which gives rise to synchronization problems and improper control of “rate of change of frequencies (ROCOF)”. Moreover, variations in weather and operating conditions adversely effect their non-linearity performance, which causes their insufficient participation towards frequency regulation along with other conventional synchronous generators. Furthermore, uncertainty associated with RES because of their intermittent nature introduces different dynamic characteristics, which increases complexity of control systems and operation. Some other concerns are degraded system inertia, high fault current, low power quality, high uncertainties, and low fault ride through capability. As a solution to these RES integration problems, cutting edge technologies including different control strategies, inertia emulation techniques, optimization techniques, energy storage devices, and fault current limiters are being practically adopted. This paper is intended to provide a comprehensive overview of challenges faced by modern power systems because of the rapidly rising RES penetrations. Further, this literature presents some practical approaches and solutions to conquer these challenges. Overall, this paper is an intensive source of information about the operational strategies and challenges of modern smart power systems including various kinds of RES as their constituents.

With the high penetration of Renewable Energy Sources (RES) in power systems, the short-circuit levels have changed, creating the requirement for altering or upgrading the existing switchgear and protection schemes. In addition, the continuous increase in power (accounting both for generation and demand) has imposed, in some cases, the need for the reinforcement of existing power system assets such as feeders, transformers, and other substation equipment. To overcome these challenges, the development of superconducting devices with fault current limiting capabilities in power system applications has been proposed as a promising solution. This paper presents a power system fault analysis exercise in networks integrating Superconducting Cables (SCs). This studies utilized a validated model of SCs with second generation High Temperature Superconducting tapes (2G HTS tapes) and a parallel-connected copper stabilizer layer. The performance of the SCs during fault conditions has been tested in networks integrating both synchronous and converter-connected generation. During fault conditions, the utilization of the stabilizer layer provides an alternative path for transient fault currents, and therefore reduces heat generation and assists with the protection of the cable. The effect of the quenching phenomenon and the fault current limitation is analyzed from the perspective of both steady state and transient fault analysis. This paper also provides meaningful insights into SCs, with respect to fault current limiting features, and presents the challenges associated with the impact of SCs on power systems protection.

With the growing penetration of grid-connected microgrids (MGs), utility grid (UG) faces the challenge of high-level fault current during fault ride-through (FRT) of MGs. To tackle this challenge, a fault current hierarchical limitation (FCHL) strategy is proposed, which consists of four levels: 1) fault current primary limitation control (FCPLC) is based on the proportional-resonant (PR) current controller; 2) fault current secondary limitation control (FCSLC) is formulated for current generation of grid-connected inverters (GCIs) with peak fault current limitation; 3) fault current tertiary limitation control (FCTLC) is formulated for the phase angle shifting of MG’s fault current to neutralize its effect on UG’s fault current; and 4) fault current quartus limitation control (FCQLC) is developed for the coordinated operation of parallel GCIs within grid code requirement. Extensive tests have validated the effectiveness of proposed strategy with a successful FRT while the MG’s output fault current has a minute effect on the UG’s fault current amplitude.

There is an increasing need for electricity utilities to limit fault levels in critical locations in power systems so that existing switchgear can continue to function as expected. This is particularly true in electrical distribution systems, where the increased penetration of renewable and decentralised generation is forcing the network to be highly interconnected in order to allow for higher integration capacity and reliable operation. Consequently, the short-circuit currents in distribution systems have increased significantly. In this background, application of fault current limiting devices is one of the solutions that is being considered by the Distribution Network Service Providers (DNSPs). A saturated core Fault Current Limiter (FCL) is one such device that can be used in existing and future electrical distribution systems to reduce the fault currents to a manageable level. This paper presents the potential performance of a saturated core FCL, in an interconnected 11kV test system, utilising a new comprehensive time-domain model to represent the FCL. PSCAD/EMTDC studies and numerical fault analysis are carried out to simulate the efficacy of an FCL when placed on a bus-tie of a looped circuit. The effect of the bus-tie FCL impedance on the network impedance and the subsequent fault current contributions is investigated. It is demonstrated that in a circuit with complex interconnections, suppression of fault currents need multiple FCLs in critical feeders.

Emission of greenhouse gases and depletion of fossil fuel reserves are two key drivers, which are forcing the mankind to generate the future energy demand from the renewable energy resources. These resources are generally distributed in nature and are directly integrated at distribution levels. Increasing penetration of the distributed energy resources in distribution power networks creates additional operational and control issues. These are mostly regulatory, economical load dispatching, power quality and protection issues.Generally power distribution systems are protected with the help of dedicated over current based protection schemes. But increasing share of distributed energy resources penetration in electric utilities poses a serious threat to the existing protection coordination schemes of the distribution systems. Distributed energy resources connected distribution networks become interconnected in nature and protection coordination schemes, which are designed for unidirectional flow of fault currents become ineffective/non-functional.Therefore, new protection coordination schemes are required for providing the adequate protection coordination for distributed energy resources connected electric power networks. In the available literature, the protection coordination schemes for radial distribution systems and developments in the area of protection coordination are discussed in detail. A thorough review for all these protection coordination schemes for distribution systems with and without distributed energy resources is done in this review article. It includes the analytical and artificial intelligence based techniques application for coordination of protective relays in the distribution systems. The limitations and research gaps in the area of protection coordination schemes are also presented in this review article.The aim of this research paper is to bring all the available research in the area of relay coordination on one platform, so that it will help the emerging researcher to identify the future scope of relay coordination application for distributed energy resources connected distribution systems.

In this paper an improved over current relay coordination protection technique is proposed. The proposed technique eliminates the sympathetic/nuisance tripping in an interconnected distribution system. Nuisance trippings are eliminated by incorporating the additional selectivity constraints in conventional over current relay coordination problem. Whenever the fault is cleared only from one end of the line in bidirectional fault feed lines, transient network configuration comes into existence. Transient network configuration causes the redistribution of fault in the distribution system and leads to further nuisance tripping of relays. This problem in this paper is solved by minimising the operating time gap between primary relays located at near end and far end of a faulty line to the best minimum possible value. The differential search algorithm is applied for optimization of highly non-linear over current relay coordination problem in this paper. The result presented in this paper shows that the proposed over current relay coordination technique is immune against the sympathetic/nuisance tripping and operating time difference between primary relays at near end and far end is also minimised within acceptable time margin successfully.

With the increasing deployment of DC power systems, particularly in DC distribution systems, there is a growing demand for rapid and effective fault current limiting solutions. Conventional fault current limiters (FCLs) often suffer from limitations in terms of response time, size, and operational complexity. As a solution to these challenges, this paper proposes a hybrid FCL based on a pyro conductor switch (PCS), which combines passive limiting elements with an active switching mechanism. The proposed PCS FCL consists of a pyro fuse, an IGBT switch, a limiting inductor, and a damping resistor. Upon fault detection, the IGBT switch is first turned off to initiate current transfer into the limiting branch. Subsequently, the pyro fuse operates by explosively severing the embedded conductor using a pyrotechnic charge, thereby providing galvanic isolation and reinforcing current commutation into a high-impedance path. This operational characteristic enables effective fault current suppression without requiring complex control or real-time sensing. A detailed analysis using PSCAD/EMTDC simulations was conducted to evaluate the current limiting characteristics under fault conditions, and a prototype was subsequently developed to validate its performance. The simulation results were verified through experimental testing, indicating the limiter’s ability to reduce peak fault current. Furthermore, the results demonstrated that the degree of current limitation can be effectively designed through the selection of appropriate current limiting parameters. This demonstrates that the proposed PCS-based FCL provides a practical and scalable solution for improving protection in DC power distribution systems.

In an effort to increase electricity supply PT PLN (Persero) build GIS Tanah Lot in Nyitdah Village Tabanan regency. The new GIS development makes the network transmission system High Voltage Air Line 150 kV changed. Changes in this transmission system impact on the channel safety settings due to changes in transmission length and impedance value. Prior to the analysis of the impedance setting, the Distance Relay Distance Zone with current, working time and OCR Relay coordination (Over Current Relay) firstly analyzes short circuit flows two phases and three symmetric phases using ETAP PowerStation program. After calculation of distance relation setting, the value of channel impedance in Tanah Lot GIS is 2,4 + j 6,96 ? with Zone 1 setting (80%): 0,200 + j 0,588 ?, Zone 2 (120%): 0,30 + j 0.882 ?, and Zone 3 (220%): 0.68 + j 2.30 ?. OCR (Over Current Relay) release time setting is indicated by releasing delay (tD>) for Tanah Lot GIS - Antosari and Tanah Lot GIS - The vessel has a value of 0.48 with an actual working time release of 1.134 seconds.

DC transmission systems are playing a more important role today. While HVDC transmission technology wins on key aspects over AC transmissions, there are still problems which make it difficult to handle and expand to grids. Among these problems is the most undesirable one: interruption of dc currents. Using DC breakers based on various principles has proved to be effective. However, the function of DC breakers is still limited due to their capacities: most of them in use now do not play like breaker which can handle fault currents. In fact, in HVDC transmission systems, DC breakers cannot handle fault currents. To interrupt fault current in orders of 10kA or above is quite demanding for currently used DC breakers. IGBT breakers might be possible solutions; however their loss cannot be ignored. Implementing fault current limiters (FCL) could be very promising if possible. The problem is that most FCL is for AC use. Currently there are more than dozens kinds of FCL technologies, varies from traditional reactors one to novel ones like high temperature superconducting (HTS) or solid state FCL. They are originally invented to reduce fault currents in AC systems, thus these FCL for DC use still calls for investigation. This paper focuses on the current FCL technologies, discusses the possibility of implementing them in DC applications, especially in DC transmission systems whose currents are considerably larger.

With the increasing power demands, size of the fault current in electrical grids is steadily increasing, and it exceeds the breaking capacity of circuit breakers. To effectively cope with these problems, a high-speed interrupter was suggested. The high-speed interrupter provides fault current with a bypass to a fault current limiter in case of accidents and consequently, fault current can be restricted. In this study, behavioral characteristics of high-speed interrupter were analyzed by accident types occurred in a distribution system. When accidents occurred, a and b contact of the high-speed interrupter were turned-off and then, turned-on. Accordingly, fault current flowed to the circuit connected to a current limiting element, and the fault current limiter restricted fault current to within a half-cycle. Nevertheless, the behavior of the high-speed interrupter was slowed down by a switching surge. As a result, fault current was confirmed to be restricted not to within the anticipated half-cycle, but to after a half-cycle. Moreover, the behavioral characteristics of the high-speed interrupter changed not only by accident types, but by behaviors of R, S, and T phases. This was due to the errors in stroke lengths of the high-speed interrupters, which resulted in a slight time discrepancy among three interrupters. In addition, the switching behaviors of the b and a contact were confirmed not to have coincided due to the switching surge; b contact behaved first and a contact followed. because of this, accuracy of stroke length and switching surges through the solenoid suction increases may be necessary to resolve.

Protection of a power system is an extremely important aspect as the duality and scheme of protection decides system reliability, controllability and stability. This paper concentrates on the protection of a distribution system in the light of developments in distributed generation (DG). The conventional distribution system is radial in nature, characterized by a single source feeding a network of down-stream feeders. The protection system has traditionally been designed assuming the system to be radial. After connecting DG, part of the system may no longer be radial, which means the coordination might not hold. The effect of DG on coordination will depend on size, type and placement of DG. This paper explores the effect of DG on protective device coordination such as fuse-fuse, fuse-recloser and relay-relay. In each case, depending on size and placement of DG, there are some margins in which the coordination may hold and certain cases, where no margin is available. These conditions are identified for each case through coordination graphs.

Due to the difficulty in power network reinforcement and the interconnection of more distributed generations, fault current level has become a serious problem in transmission and distribution system operations. The utilization of fault current limiters (FCLs) in power system provides an effective way to suppress fault currents and result in considerable saving in the investment of high capacity circuit breakers. In a loop power system, the advantages would depend on the numbers and locations of FCL installations. This paper presents a method to determine optimum numbers and locations for FCL placement in terms of installing smallest FCL parameters to restrain short-circuit currents under circuit breakers' interrupting ratings. In the proposed approach, sensitivity factors of bus fault current reduction due to changes in the branch parameters are derived and used to choose candidates for FCL installations. A genetic-algorithm-based method is then designed to include the sensitivity information in searching for best locations and parameters of FCL to meet the requirements. Test results demonstrate the efficiency and accuracy of the proposed method.

An EMTP RV based study to limit fault currents in a distribution system using a 3-phase version of a solid-state fault current limiter (SSFCL) is presented. For demonstration purposes, two types of distribution systems have been considered: a single-source radial system and a multiple-source distribution system with a bus-tie. Simulations have been done for different types of faults to show that the SSFCL is effective for limiting fault currents. Comparisons are also made with a single-phase version of the SSFCL which had been previously presented.

The integration of renewable energy sources (RESs) cannot be postponed given the several techno-economic and environmental factors. However, the intermittent nature of RESs brings several challenges because such sources introduce significant operational variability and uncertainty in the system. Framed in this context a new stochastic mathematical planning model is proposed considering the placement and sizing of energy storage systems and reactive power sources that altogether enable high penetration of RESs. The model employs a linearized AC model, balancing well accuracy with computational burden. The model is tested on a standard distribution network system. Numerical results show that the simultaneous integration of energy storage systems and reactive power sources largely leads to a substantially increased penetration of RESs in distribution systems. Furthermore, dramatic reductions in losses, system costs and emissions are observed. Results analysis also reveal the positive contribution of such a planning on the overall voltage stability in the system.