A new approach is proposed to solve the directional overcurrent relay coordination problem, which arises from installing distributed generation (DG) in looped power delivery systems (PDS). This approach involves the implementation of a fault current limiter (FCL) to locally limit the DG fault current, and thus restore the original relay coordination. The proposed restoration approach is carried out without altering the original relay settings or disconnecting DGs from PDSs during fault. Therefore, it is applicable to both the current practice of disconnecting DGs from PDSs, and the emergent trend of keeping DGs in PDSs during fault. The process of selecting FCL impedance type (inductive or resistive) and its minimum value is illustrated. Three scenarios are discussed: no DG, the implementation of DG with FCL and without FCL. Various simulations are carried out for both single- and multi-DG existence, and different DG and fault locations. The obtained results are reported and discussed.
"The time dial setting and pickup current setting are determined for each relay provided that certain coordination constraints are met . For this purpose, a two-phase optimization model is mathematically formulated in (3)–(9) . In Phase 1, the objective J given in (3) is minimized subject to the set of constraints given in (4)–(6). "
[Show abstract][Hide abstract] ABSTRACT: This paper addresses the problem of overcurrent relays (OCRs) coordination in the presence of DGs. OCRs are optimally set to work in a coordinated manner to isolate faults with minimal impacts on customers. The penetration of DGs into the power system changes the fault current levels seen by the OCRs. This can deteriorate the coordinated operation of OCRs. Operation time difference between backup and main relays can be below the standard limit or even the backup OCR can incorrectly work before the main OCR. Though resetting of OCRs is tedious especially in large systems, it cannot alone restore the original coordinated operation in the presence of DGs. The paper investigates the optimal utilization of fault current limiters (FCLs) to maintain the directional OCRs coordinated operation without any need to OCRs resetting irrespective of DGs status. It is required to maintain the OCRs coordination at minimum cost of prospective FCLs. Hence, the FCLs location and sizing problem is formulated as a constrained multi-objective optimization problem. Multi-objective particle swarm optimization is adopted for solving the optimization problem to determine the optimal locations and sizes of FCLs. The proposed algorithm is applied to meshed and radial power systems at different DGs arrangements using different types of FCLs. Moreover, the OCRs coordination problem is studied when the system includes both directional and non-directional OCRs. Comparative analysis of results is provided.
"In the coordination problem of DOCRs, the main aim is to determine the TSM and plug setting (PS) of each relay, so that the OF is minimized, subjected to limits on problem variables and certain coordination constraints. The main OF that is already used in most of the literature is the total weighted sum of OTs of primary relays as follows   : "
[Show abstract][Hide abstract] ABSTRACT: This paper presents a new method for coordination of directional overcurrent relays to reduce the discrimination time of the primary and backup relays, by using nondominated sorting genetic algorithm-II (NSGA-II). In order to achieve a reliable protective system, it is necessary to find a solution to avoid having large discrimination times, in addition to coordination time interval (CTI). The novelty of the paper is to reduce the discrimination time of the primary and backup relays and simultaneously reduce the operating time of primary and backup relays, by introducing a new method. In contrast to the conventional intelligent methods, the proposed method does not require weighting factors for conversion of multi-objective function into an equivalent single objective function. The effects of both near and far-end faults are considered to solve the proposed problem formulation. Also, various overcurrent relays characteristics are considered within the program to select the best of them for each relay by optimization algorithm. The proposed method is implemented in three different test cases, i.e. three, eight and IEEE 30-bus network. The results are compared with previously proposed methods.
Electric Power Systems Research 02/2015; 119:228–236. DOI:10.1016/j.epsr.2014.09.010 · 1.75 Impact Factor
"Therefore, in this research, a novel method based on KF is proposed for fault location. Fault current limiters (FCLs) are another suitable alternative of the relays utilized in , which can quickly limit fault current after fault occurrence , . Furthermore, protection relays result in perfect segregation of faulty sections from the network , while FCL can preserve the integrity of the network's sections . "
[Show abstract][Hide abstract] ABSTRACT: Abstract— Penetration of Distributed generations (DG) are becoming more and more widespread in the current electric power networks. One of the most important issues regarding utilization of DG in power systems is related to their impact on fault current level. In this regard, a multi-agent-based fault current limiting scheme for microgrids is presented in this paper. A typical microgrid is divided into several sections. A number of Superconducting Fault Current Limiters (SFCLs) which are located in suitable locations of the network, can suppress transient fault currents. Fault location is identified using several Fault Location Identification Units (FLIUs), which are installed in suitable places. In each FLIU, fault current is estimated using a Kalman filter and then residual signal is generated from the calculated and measured fault current. In fault condition, faulty section is identified by analyzing the information of FLIUs in the network. Then, the impact of the faulty section on the sound sections is minimized by utilizing the proposed fault current limiting scheme. Capabilities of the proposed method are evaluated using different simulations on a benchmark microgrid.
IEEE Transactions on Power Delivery 01/2013; 29(2). DOI:10.1109/TPWRD.2013.2282917 · 1.73 Impact Factor
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