Sequence Of Switching Operations Research Articles

Switching Device-Cognizant Sequential Distribution System Restoration

This paper presents an optimization framework for sequential reconfiguration using an assortment of switching devices and repair process in distribution system restoration. Compared to existing studies, this paper considers types, capabilities and operational limits of different switching devices, making it applicable in practice. We develop a novel multi-phase method to find the optimal sequential operation of various switching devices and repair faulted areas. We consider circuit breakers, reclosers, sectionalizers, load breaker switches, and fuses. The switching operation problem is decomposed into two mixed-integer linear programming (MILP) subproblems. The first subproblem determines the optimal network topology and estimates the number of steps to reach that topology, while the second subproblem generates a sequence of switching operations to coordinate the switches. For repairing the faults, we design an MILP model that dispatches repair crews to clear faults and replace melted fuses. After clearing a fault, we update the topology of the network by generating a new sequence of switching operations, and the process continues until all faults are cleared. To improve the computational efficiency, a network reduction algorithm is developed to group line sections, such that only switchable sections are present in the reduced network. The proposed method is validated on the IEEE 123-bus and 8500-bus systems.

A two‐stage service restoration method for electric power distribution systems

Improving the reliability of power distribution systems is critically important for both utilities and customers. This calls for an efficient service restoration module within a distribution management system to support the implementation of self-healing smart grid networks. Although the emerging smart grid technologies, including distributed generators (DGs) and remote-controlled switches, enhance the self-healing capability and allow faster recovery, they still pose additional complexity to the service restoration problem, especially under cold load pickup (CLPU) conditions. Herein, a novel two-stage restoration framework is proposed to generate a restoration solutions with a sequence of control actions. The first stage generates a restoration plan that supports both the traditional service restoration using feeder reconfiguration and the grid-forming DG-assisted intentional islanding methods. The second stage generates an optimal sequence of switching operations to bring the outaged system quickly to the final restored configuration. The problem is formulated as a mixed-integer linear program that incorporates system connectivity, operating constraints, and the CLPU models. It is demonstrated that on using a multi-feeder test case, the proposed framework is effective in utilizing all available resources to quickly restore the service and generate an optimal sequence of switching actions to be used by the operator to reach the desired optimal configuration.

Network reconfiguration and DG output including real time optimal switching sequence for system improvement

ABSTRACT This research proposes an optimal switching sequence path method in order to minimise power losses during the network switching operation. Apart from this contribution, simultaneous optimal network reconfiguration and optimal DG output generation were also presented. The proposed methodology involves (1) optimal radial network reconfiguration and DG output simultaneously and (2) real time optimal sequence of switching operations required to convert the network from the original configuration to the optimal configuration obtained from (1). The proposed method is applied to reduce power losses and improve the overall voltage profile of the system. The chosen optimisation techniques include (EP), (PSO), (GSA), and (FA). To assess the capabilities of the proposed method, simulations using MATLAB were carried out on IEEE 33-bus and IEEE 69-bus radial distribution networks. The obtained results demonstrate the effectiveness of the proposed strategy to determine the sequence path of switching operations, as well as the optimal network configuration and optimal generation output of DG units. For more validation, real-time analysis test using PSCAD/EMTDC software is used to check the voltage stability of the system during switching process. The test proved that the optimal switching sequence does not cause over voltage or under voltage when implemented in real-time conditions.

Optimal switching sequence path for distribution network reconfiguration considering different types of distributed generation

Minimizing power losses in a distribution system is commonly realized through optimal network reconfiguration. In the past, network reconfiguration research was focused on planning, where the final configuration with the lowest power losses was the main goal. However, power losses during switching operations from the initial state to the final state of the configuration were not considered. This paper presents the optimal switching sequence path to minimize power losses during the network switching operation. Apart from this contribution, the simultaneous optimal network reconfiguration for variable load network and distributed generation (DG) output is also proposed. The proposed methodology involves the (i) optimal network reconfiguration with variable load and DG output simultaneously, and (ii) the optimal sequence of switching operations required to convert the network from the original configuration to the optimal configuration obtained from (i). The selected optimization technique in this work is the firefly algorithm. To assess the capabilities of the proposed method, simulations using MATLAB are carried out on IEEE 33‐bus radial distribution networks. The results demonstrate the effectiveness of the proposed strategy to determine the sequence path of switching operations, as well as the optimal network configuration and optimal output of DG units. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

An Improved Service Restoration Algorithm under Consideration of Abnormal Conditions in Distribution Automation Systems

The most important function in distribution automation system (DAS) is the service restoration. KEPCO's current service restoration provides a very effective restoration service. However, it has been developed without the consideration of unexpected abnormal conditions that may occur while processing the sequence of switching operations. The objective of this paper is to provide practical service restoration schemes under consideration of abnormal conditions. The proposed service restoration schemes have been integrated to a branch office (B/O) in KEPCO. The proposed method strongly supports the conventional service restoration and adds to its value.

Differential evolution using ancestor tree for service restoration in power distribution systems

Problems in power distribution system reconfiguration (PDSR), such as service restoration, power loss reduction, and expansion planning, are usually formulated as complex multi-objective and multi-constrained optimization problems. Several evolutionary algorithms (EAs) have been developed to deal with PDSR problems, but the majority of EAs still demand high running time when applied to large-scale distribution systems (thousands of buses and switches). This paper presents a new approach for service restoration in large scale distribution systems that employs a discrete differential evolution with ancestor tree (DE-Tree). We combine the node-depth encoding (NDE) to represent computationally the electrical topology of the system and the ancestor tree presented here to implement differential evolution for service restoration problems. The ancestor tree is used to build a list of elementary movements that maps one solution in the search space into another, thus capturing the “difference” between forests encoded with the NDE, which is essential in the search engine of differential evolution. The use of an ancestor tree is not only central to implement differential mutation in our algorithm but also can track the sequence of switching operations in the restoration of the system after the optimization process is finished. The proposed approach makes differential evolution suitable for treating combinatorial optimization problems related to PDSR. Results presented on distribution system reconfiguration problems suggest the benefits and fast convergence of the proposed approach.

Topology Control for Load Shed Recovery

This paper introduces load shed recovery actions for transmission networks by presenting the dc optimal load shed recovery with transmission switching model (DCOLSR-TS). The model seeks to reduce the amount of load shed, which may result due to transmission line and/or generator contingencies, by modifying the bulk power system topology. Since solving DCOLSR-TS is computationally difficult, the current work also develops a heuristic (MIP-H), which improves the system topology while specifying the required sequence of switching operations. Experimental results on a list of N-1 and N-2 critical contingencies of the IEEE 118-bus test case demonstrate the advantages of utilizing MIP-H for both online load shed recovery and recurring contingency-response analysis. This is reinforced by the introduction of a parallelized version of the heuristic (Par-MIP-H), which solves the list of critical contingencies close to 5x faster than MIP-H with 8 cores and up to 14x faster with increased computational resources. The current work also tests MIP-H on a real-life, large-scale network in order to measure the computational performance of this tool on a real-world implementation.

New algorithm for reconfiguration and operating procedures in electric distribution systems

This paper presents a step-by-step heuristic algorithm for the reconfiguration of radial electrical distribution systems, aiming at power loss minimization. The proposed methodology is based on a Dynamic Switches Set approach, which is updated due to topological changes in the electrical network and to avoid the premature convergence of the algorithm in suboptimal solutions. Moreover, the proposed algorithm considers the demand variation through the system load curves and determines the sequence of switching operations during the reconfiguration process to obtain feasible operation points in the intermediate stages of this process. The network state in each reconfiguration stage is analyzed using a conventional power flow algorithm. The proposed methodology is applied to systems from the literature to evaluate its effectiveness.

Enumerating Cube Tilings

Cube tilings formed by $$n$$ -dimensional $$4\mathbb Z ^n$$ -periodic hypercubes with side $$2$$ and integer coordinates are considered here. By representing the problem of finding such cube tilings within the framework of exact cover and using canonical augmentation, pairwise nonisomorphic 5-dimensional cube tilings are exhaustively enumerated in a constructive manner. There are 899,710,227 isomorphism classes of such tilings, and the total number of tilings is 638,560,878,292,512. It is further shown that starting from a 5-dimensional cube tiling and using a sequence of switching operations, it is possible to generate any other cube tiling.

Optimization approach to dynamic restoration of distribution systems

The problem of fault restoration in distribution systems is a multi-objective dynamic combinatorial problem with topology constraints. The problem consists in finding both (1) an admissible post-fault configuration and (2) the sequence of switching operations to reach such configuration. Research on the problem solution has been focusing on the search for admissible post-fault configurations; the sequencing of switching operations is usually disregarded. However, the sequencing of switching operations determines the admissibility of the intermediate configurations and therefore the effectiveness of the overall restoration plan. In this paper, we propose to address the problem of fault restoration in distribution systems in a two phase approach. In the first phase a network optimization evolutionary approach is proposed to find the optimal post-fault configuration. In the second phase a dynamic programming approach is proposed to determine the optimal sequence of switching operations. The two phase approach is illustrated with an example from a real urban distribution network.

Frequency domain transient analysis of electrical networks including non-linear conditions

This paper describes a method for the analysis of electromagnetic transients in multiphase transmission networks using the Numerical Laplace Transform. The proposed procedure is based on the superposition principle and is applied to switching and non-linear elements modeling. Switching operations are modeled as initial condition problems by means of injected current sources. In the case of non-linear elements, a piece-wise linear approximation is made, which reduces the problem to a sequence of switching operations. Several applications and comparisons with results obtained with the EMTDC and ATP programs are presented.

An Algorithm of Making Switching Operation Sequence for Fault Testing using Tree Structured Data

This paper describes an algorithm of making switching operation sequence for fault testing using tree structured data. When the faulty section is not isolated exactly, faulty section is tested whether the fault exist in the section by energizing. The proposed algorithm can determine appropriate order of components for fault testing and valid switching operation sequence for each fault testing. An example shows the effectiveness of the proposed algorithm. The proposed algorithm is used at actual control centers.

An expert system for switch operation planning on line dispatching

AbstractAn expert system is presented that produces the operation sequence for disconnecting apparatus from a power system under normal operating conditions.To maintain the reliability of power supply on the network during the operation, the operation sequence must be produced in due consideration of network states, such as load factors and routes of transmission line. Besides, since the network which the system manages includes many high‐voltage consumers, the operation sequence for each consumer should be divided into detailed switch operation sequence.To produce a detailed switching operation sequence simultaneously with macronetwork operation sequence, we introduce the multilayered object‐oriented network model for the knowledge base of this expert system.Each layer of this model represents network configuration in the different degree of detail, and the consistency between states of layers is maintained by an interlayer message‐passing mechanism. On the layer which represents apparatus and their connections in detail, the inference engine can generate the switching operation sequence. On another layer which represents control centers and consumers, the inference engine can search for routes of power supply and can generate the sequence of changing over the network. Therefore, by using each layer properly, the inference engine can produce various kinds of operation sequences.Furthermore the object‐oriented network model facilitates maintenance and extension of the system.

作業時操作手順自動作成システム

An expert system is presented that produces the operation sequence for disconnecting apparatus from a power system under normal operating conditions. To maintain the reliability of power supply on the network during the operation, the operation sequence must be produced in due consideration of network states, such as load factors and routes of transmission line. Besides, since the network which the system manages includes many high-voltage consumers, the operation sequence for each consumer should be divided into detailed switch operation sequence. To produce a detailed switching operation sequence simultaneously with macronetwork operation sequence, we introduce the multilayered object-oriented network model for the knowledge base of this expert system. Each layer of this model represents network configuration in the different degree of detail, and the consistency between states of layers is maintained by an interlayer message-passing mechanism. On the layer which represents apparatus and their connections in detail, the inference engine can generate the switching operation sequence. On another layer which represents control centers and consumers, the inference engine can search for routes of power supply and can generate the sequence of changing over the network. Therefore, by using each layer properly, the inference engine can produce various kinds of operation sequences. Furthermore the object-oriented network model facilitates maintenance and extension of the system.

On-line expert system for power distribution system control

The application of expert systems in power systems has attracted much attention both academically and industrially. This paper reports on the development, testing, and commissioning of an expert system for the on-line control of a distribution network. The expert system is used to determine the optimal switching operation sequence for load rerouting during fault restoration, emergency operation overload relieving, and network maintenance planning. The main features of the system can be summarized as follows. Employment of hierarchical structure of knowledge base decision tree, introduction of function-oriented and network scale-oriented rules, easily changable priorities used during decision making can be done using a CRT display, in addition to the facility of changing the network operating constraints. The results of such changes can be evaluated by a built-in simulator using a snapshot of the on-line data. A tracing facility is also introduced to trace the reasoning during the decision making process. The techniques used, development process, system evaluation and testing are reported.

A portable instrument for measuring the electrical conductivity of aviation fuels

This paper describes an instrument designed to measure the electrical conductivity of aviation fuels on airfields. It is compact, robust and portable, yet its accuracy is almost as good as that of laboratory instruments; the 95% confidence limits of a measurement are ±0.45 picomho m-1. The principle of operation is to measure the decay of voltage between the plates of a cylindrical condenser whose dielectric is the liquid under test. A radiation dosimeter is modified to act as an electrostatic voltmeter and a clockwork timer provides a fixed sequence of switching operations. Measurements only take a few minutes and can be made by non-technical operators.