Coordination of directional overcurrent relays in transmissionsystems-a subsystem approach

A new concept, called subsystem coordination, for efficiently computing proper settings of directional overcurrent relays on transmission systems in response to changes in system topology and load levels is proposed. An automatic window identification and coordination algorithm has been developed, implemented, and tested on a realistic transmission system. The test results have been validated through a full system coordination study, and the significant reduction in computer time required by the subsystem approach has been demonstrated     

Optimal coordination of directional overcurrent relays ininterconnected power systems

The authors present a new methodology based upon the principles of optimization theory, to treat the problem of optimal coordination of directional overcurrent relays in interconnected power systems. With the application of the proposed technique, this coordination problem is stated as a parameter optimization problem, which in general, is of a large dimension, especially when many different system configurations and perturbations are to be considered. Several optimization procedures, including direct methods and decomposition techniques, for solving this large scale coordination problem are described, and results of optimally coordinating directional overcurrent relays in power systems with up to 30 buses are presented     

Controlled switching of electrical AC circuits by reed relays

Principles of the controlled (synchronous) switching (near zero of the load current) by reed relays of electric AC circuits, electric circuits that embody these principles, as well as the mathematical expressions that determine the parameters of these circuits are considered. Experimental results that have shown good agreement with the theoretical study are shown.     

Computer aided coordination of directional relays: determination ofbreak points

The directional overcurrent and distance relays of a multiloop network must be set in a sequence to ensure coordination. The starting points of the sequence are called break points. An algorithm to determine the minimum number of break points is presented. It can be readily implemented on a computer and forms a basic component of a computer-aided-design package for a protective system     

Optimal computation of distance relays second zone timing in amixed protection scheme with directional overcurrent relays

This paper describes a technique to determine the optimal time setting for the second zone of distance relays when used in a mixed protection scheme with directional overcurrent relays. The technique consists of including the second zone operation time as a new variable in the original problem statement of optimal computation of directional overcurrent relays settings. It is shown that the influence of distance relays and directional overcurrent relays must be considered when the settings of these relays are computed. Numerical results obtained with the proposed method for a realistic power system are presented     

Optimal coordination of directional overcurrent relays consideringdefinite time backup relaying

A methodology is presented for the consideration of definite-time backup relays in the optimal coordination of directional overcurrent relays using linear programming. It is shown that the influence of considering second-zone distance relays and breaker failure relays impose important requirements for the determination of the time dial settings of directional overcurrent relays. The paper introduces a revised formulation of the optimization problem. Results are presented for the application of the methodology on a power system with 2 generators, 9 buses, 2 transformers and 7 transmission lines     

Optimal coordination of directional overcurrent relays consideringdynamic changes in the network topology

This paper presents a method to consider the dynamic changes in the network's topology for the coordination of directional overcurrent relays using linear programming. The proper coordination constraints are included by using linear approximations for the relay dynamics. The application of the methodology as well as the importance of considering the transient configuration changes are illustrated with a practical example and a test case consisting of a real industrial power system     

Finding all solutions of piecewise-linear circuits

A new algorithm is given for solving the d.c. piecewise-linear equations of non-linear electronic circuits. The device models are assumed, with little loss of generality, to be made of 2-terminal piecewise-linear resistors and linear controlled sources. Unlike other methods, this algorithm guarantees that all solutions will be found in a finite number of steps. The method depends crucially on a recent development which allows a multi-dimensional piecewise-linear function to be represented in a closed canonical form. This highly compact representation requires only a minimum amount of computer storage and is responsible for the efficiency of the algorithm.     

Comprehensive coordination of combined directional overcurrent and distance relays considering miscoordination reduction

This paper presents a novel approach to solve the miscoordination problem of combined directional overcurrent and distance relays in transmission and subtransmission systems. In order to reduce relays miscoordinations, a general objective function is presented to find optimum directional overcurrent relays time setting multipliers, characteristics, and pickup currents by optimization algorithms. In previous researches, different approaches have been presented but they cannot find a reliable solution to avoid from having negative discrimination times between the backup and main relay (miscoordination), which means operation of the backup relay before the main relay. Using proposed approach, not only the number of miscoordinations can be greatly decreased but also the positive discrimination times can be minimized. The proposed method is tested on 9-bus and 39-bus test system. Genetic algorithm and human behavior-based optimization are used as optimization tools to find optimum settings. The results indicate that the proposed approach is capable of solving the miscoordination problem, in addition to minimization of discrimination and relay operation times compared with previous approaches.     

Coordination of directional overcurrent relay timing using linearprogramming

A successive linear programming methodology is presented to treat more effectively those applications where a local structure change is performed to a power system already in operation, and where the modification of the settings of already existent relays is not desirable. The dimension of the optimization problems to be solved is substantially reduced, and a sequence of small linear programming problems is stated and solved in terms of the time dial settings, until a feasible solution is reached. With the proposed technique, the number of relays of the original system to be reset is reduced substantially. It is found that there is a trade-off between the number of relays to be reset and the optimality of the settings of the relays     

Applying the directional neutral, 67N, function in microprocessor multifunction relays

This paper is a case study of the application of the 67N function in a digital multifunction relay. The directional neutral current relay, function number 67N, is often found to be critical to the proper operation of a protective scheme. Furthermore, a false trip of a 67N will usually be devastating. The 67N is a complex function that always required more wiring than almost any other relay. The 67N is now available as one of many functions in digital multifunction relays. However, the digital 67N may be even more difficult to set and test than it was as a single function in an old electromechanical relay.     

Optimal coordination of directional over-current relays using Teaching Learning-Based Optimization (TLBO) algorithm

Relay Coordination in a big distribution system with multiple meshes and bidirectional power feed becomes very Complex for protection engineers. Manual and graph theory based approaches were applied successfully in small power system. In a big distribution system linear and non-linear programming based optimizing techniques are applied for relay coordination. Presently, artificial intelligence techniques are applied for optimal co-ordination of directional overcurrent relays. This paper discusses the application of Teaching Learning Based Optimization (TLBO) algorithm for optimal coordination of DOCR relays in a looped power system. Combination of primary and backup relay is chosen by using Far vector of LINKNET structure, to avoid mis-coordination of relays. Coordination of DOCR is tested for IEEE 3, 4 and 6 bus systems using the TLBO. Also, the objective function is modified to optimize the operating time between backup and primary relays. The results are compared with the optimized values of Time dial setting and Plug setting values obtained from modified differential evolution algorithm. The proposed algorithm TLBO gives optimal coordination margin between 0.3 and 0.8 s and no miscoordination between primary and backup pairs. Results are also verified using Digsilient power factory simulation software.     

Performance analysis of all optical-based quantum internet circuits

Journal of Computational Electronics - A Quantum dot implanted within a double-sided optical microcavity is considered and investigated as a critical component for all optical-based quantum...     

Dual-setting directional over-current relays: An optimal coordination in multiple source meshed distribution networks

To guarantee a safe operating scheme against the probable faults, an accurate and fast relaying scheme is of high priority. This challenge seems to be more sophisticated in multiple source meshed distribution networks hosting distributed generations (DGs). In this case, the current experiences bidirectional flows. More recently, dual-setting over-current relays are evolved as competent countermeasures for such cases. In this way, establishing an optimal coordination strategy is recognized as the first prerequisite in assuring a safe protection scheme. To this end, the present study aims at minimizing the overall operating time of primary and backup relays. Typically, the coordination problem is carried out by adjusting two parameters namely, pick up current (Ip) and time dial setting (TDS). In contradiction, the proposed approach follows a user-defined settings supported by some operating rules. Thus, besides the aforementioned settings, the coefficients of the inverse-time characteristics are also optimized. In other words, more flexibility is attained in adjusting relay’s characteristic in regard of the network’s loading and topological changes. Furthermore, inclusion of operating rules in main objectives, not only reduces the sum of operating time of all relays, but also increases the efficiency of backup relays regarding the break points in meshed networks. In other words, the covering zone by each backup relay is increased. The proposed approach demonstrates a non-linear programming fashion which is tackled based on genetic algorithm (GA). Several numerical studies are carried out to interrogate the validity of the proposed approach encountering different fault scenarios. The obtained results are encouraging.     

An interior point method based protection coordination scheme for directional overcurrent relays in meshed networks

In this work, interior point method based protection coordination schemes are presented for coordinating directional overcurrent relays. Also, for minimizing the operating times of primary and backup relays simultaneously, a new objective function (NOF) is developed. The effectiveness of the proposed solution methods and the developed objective function has been investigated on two test systems (one small and one large). The suitability of the proposed method for coordination of directional overcurrent relays in meshed networks has been established by comparing its performance with that obtained by genetic algorithm, differential evolution and two hybrid algorithms for the developed objective function. Also, the superiority of the develop objective function has also been established by comparing the protection coordination results obtained by using NOF with those obtained by the other objective functions reported in the literature.     

Presolve analysis and interior point solutions of the linear programming coordination problem of directional overcurrent relays

A linear programming interior point algorithm is proposed for the solution of the problem of coordinating directional overcurrent relays in interconnected power systems considering definite time backup relaying. The proposed algorithm is a variation of the primal–dual approach that uses multiple correctors of centrality. Pre-solution problem filtering simplification techniques are used prior to the application of the linear programming algorithm. Results are presented for the application of the methodology on a realistic test case, a 115–69 kV power system with 108 buses, 86 lines, 61 transformers, and 97 directional overcurrent relays. Optimal solutions are found in an automatic fashion, using the algorithm for the settings of the ground relays as well as for the phase relays. The application of the pre-solution problem simplification techniques is highly recommended, resulting in a significant reduction of the size and complexity of the linear programming problem to be solved. The interior point approach reaches a feasible point in the close vicinity of the final optimal result in only one or two iterations. This fact represents an advantage for on-line applications. The proposed methodology and in particular the use of the presolve problem simplification techniques is shown as a new valuable tool for the setting of directional overcurrent relays in interconnected power systems.     

A new approach for optimal coordination of distance and directional over-current relays using multiple embedded crossover PSO

Proper coordination between distance relays and Directional Over-Current Relays (DOCRs) in power systems is one of the important conditions for the system security. The coordination problem in interconnected systems, because of complexity of the system, is complicated and a powerful optimization program must be used in order to do the best and optimal relay coordination.In this paper at first, a new problem formulation for optimal coordination of distance relays in presence of DOCRs, as the backup relays, is proposed. Then to deal with this complex problem, as another contribution, a new Multiple Embedded Crossover PSO (MECPSO) is proposed. In the presented MECPSO by updating velocity vector, diversity of the swarm is enhanced and exploration and global search capabilities of the PSO is improved as well. In the proposed approach, with considering the effect of in-feed or out-feed currents, the optimal second zone timing of distance relays and optimal settings of DOCRs are computed. The proposed method is tested on two case studies and encouraging optimal results are obtained.     

Mechanism of simultaneous tripping of ground directional relays in a 6.6‐kV distribution system

In Kyushu Electric Power's 6.6‐kV distribution system, after a single‐phase ground fault occurred in the circuit of a distribution line, we experienced a phenomenon in which the analogue ground directional relays of the other circuits linked to the same bank were simultaneously tripped. In this paper, focus is placed on the mechanism and possibility of simultaneous tripping of ground directional relays. This mechanism was examined in an experiment carried out using an analogue simulator. The results of the test revealed that such simultaneous tripping was attributable to the neutral instability phenomenon of grounding potential transformers installed in an isolated neutral system. © 2010 Wiley Periodicals, Inc. Electr Eng Jpn, 171(2): 23–30, 2010; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20919     

Coordination of relays, reclosers, and sectionalizing fuses foroverhead lines in the oil patch

Overhead distribution systems used in oil pumping and secondary recovery installations present a challenge to the engineer in obtaining protective device coordination between sectionalizing fuses, line reclosers, and feeder breakers. Ways of obtaining solutions to these problems, especially as related to upgrading existing substation and feeder line protection on medium voltage systems, are proposed. It is noted that a coordination analysis of an oil-patch distribution system involves application of engineering principles, manufacturing data, standards and/or codes, and knowledge of production practices. The objective of the analysis always is to see what can be done to protect equipment, maximize production (minimize outages and downtime), and maintain ease of operation, all at a minimum overall cost. The authors recommend that a PCIC/IEEE working group be formed for the purpose of reviewing oil patch distribution systems specific requirements. The ultimate objective would be to develop appropriate electrical standards and recommended practices for the production industry