Topology Processor Research Articles

Bus Split Contingency Analysis Implementation in the NetVision DAM EMS

Implementation of the bus coupler outage scenarios in the NetVision DAM energy management system (EMS) contingency analysis is presented in this paper. In order to identify the bus coupler branches in the network model, the existing topology processor was upgraded. The description of the topological algoritm for detection of the bus couplers is given. Based on the toppology analysis results, calculation subnodes are created. Calculation model was modified in order to include the bus couplers and the subnodes as the new calculation objects. These modifications are fundamental for the introduction of the bus coupler outages in the contingency analysis. Implications of the bus coupler outages on the load flow mathematical model are discussed. Implemented NetVision DAM solution for the analysis of such outage scenarios is presented.

Power Data Quality Improvement Through PMU Bad Data Detection Based on Deep Complex Network

Phasor Measurement Units (PMUs) enable the switching of devices in various power signal modes. A jitter or glitch in a signal cause bad data and also the PMU data will spike due to a disturbance or a transmitting data mistake. As a result of these difficulties, PMU data suffer from different degrees of data quality problems. To detect the bad data, several approaches have been already utilized however it provides some disadvantages such as complexity due to the utilization of dual identical systems separately for analyzing both real and imaginary values of PMU. Likewise, the bad data due to the topology variations have not been optimally identified. To overcome these issues a Robust Bad Data Detection Technique has been proposed in which a Deep complex neural network (DCNN) is incorporated to process the complex number having both voltage magnitude and phase angle. Deep complex Networks are also proposed with the conjunction of topology processor and AC state estimator (SE). Moreover, instead of Batch normalization weight normalization is altered due to the fusion of recurrent timestamps for measuring voltage magnitude and phase angle. The comparative analysis is done in terms of accuracy , Bad data detection capability , bad data detection range and running time with existing techniques The proposed technique provides accuracy of about 99.5% which is higher than the existing techniques.

Distributed Application Architecture and LinkNet Topology Processor for Distribution Networks Using the Common Information Model

A distributed application architecture for communication and control of distribution network assets is introduced. The architecture is based on the physical topology of the feeder instead of communications network layers, with creation of individual areas of responsibility for distributed application agents based on the concept of switch-delimited topological areas. Implementation of the architecture in standards-based platforms is enabled by a robust graph-based topology processor leveraging the class structure of the Common Information Model (CIM). The topology processor creates a set of LinkNet linked list structures for indexing of CIM class object instances and mapping of the feeder topology in real-time. The data structures and algorithm are computationally lightweight, with performance tests presented for several IEEE distribution test systems.

Topology Processor design for EHV Substations

The intelligent application is one of the major issues in power system research. The topology identification is one of the most important modules to develop intelligent system such as fault diagnosis and restoration expert system. This paper presents the topology processor in order to identify topology effectively in a practical 765kV substation in Korea composed of the double-bus and 1.5 CB, which is the typical structure of EHV substations. The proposed topology processor redefines switching group composed of circuit breaker, disconnecting switches and ground switches as aggregated circuit breaker. The proposed system remarkably reduces the search space and search time for topology identification. The proposed topology processor is developed using the data of a practical 765kV substation in Korea. The proposed system can be applied to intelligent systems such as fault diagnosis and restoration expert system and contribute to improving the performance of intelligent systems.

Static State Estimation Without Topology Processor

A state estimation framework that eliminates the need for a topology processor is presented in this paper. By retaining switching devices (SDs) in the network model, this approach allows estimation of their statuses. Consequently, topology error detection becomes part of the SE process. Since this approach requires expansion of bus-branch models with SDs, the conventional state estimation formulation is accordingly modified to avoid numerical issues due to extremely small (large) impedance values of open (closed) switching devices. The scalability of the proposed framework is achieved by parallel processing, which is implemented after partitioning the system into zones. The measurement overhead is kept minimal by utilizing two optimal measurement placement algorithms and taking advantage of KCL-based virtual measurements. Case studies presented show that the proposed method can identify concurrent bad data and topology errors. The improvements in computation times due to parallel processing are demonstrated through simulations on the IEEE 300-bus system with and without zone-partitioning.

Restoration Aid Expert System for Power Systems

This paper propose an intelligent restoration aid system that assists the decision of power system operators for reliable and fast restoration processes when a blackout happened in massive power systems. This system consists of a topology processor and intelligent restoration aid system. The topology processor identifies the real-time embedded topology structure between power system facilities and determines the power outage section. The power system restoration aid system determines the feasible restoration path in terms of overloads and real power flow. Case studies demonstrate a promising possibility of practical application.

Application of a Phasor-Only State Estimator to a Large Power System Using Real PMU Data

This paper applies a phasor-only state estimator (PSE) to a large power system consisting of two control regions, using synchrophasor data from 56 765/345/230 kV substations. Although the technique has been previously developed, this paper describes a topology processor to determine the redundant clusters of connected buses such that the PSE can be used in real time. This PSE allows corrections for phase biases, transformer taps, and current magnitude scaling. The ability to simultaneously solve the PSE for the two control regions is due to a PMU monitoring a tie-line between these two regions. The results show that with this method, the total vector errors of the measured voltage phasor data in these two control regions average to less than 0.5% under ambient conditions. The PSE also computes virtual phasor measurements on 70 buses that do not have PMUs, including large steam generator and wind-turbine generator substations.

Line outage contingency analysis including the system islanding scenario

The paper describes an algorithm for determining the line outage contingency of a line taking into account of line over load effect in remaining lines and subsequent tripping of over loaded line(s) leading to possible system split or islanding of a power system. The optimally ordered sparse [ Bʹ ], [ Bʺ ] matrices for the integrated system are used for load flow analysis to determine modified values of voltage phase angles [d] and bus voltages [V] to determine the over loading effect on the remaining lines due to outage of a selected line outage contingency. In case of over loading in remaining line(s), the over loaded lines are removed from the system and a topology processor is used to find the islands. A fast decoupled load flow (FDLF) analysis is carried out for finding out the system variables for the islanded (or single island) system by incorporating appropriate modification in the [ Bʹ ] and [ Bʺ ] matrices of the integrated system. Keywords: Contingency; Line outage; Rotating mass; System islanding

Modelling and Simulation of a Variable Step Size Algorithm for a Power Simulator

The Dispatcher Training Simulator (DTS) is used for imparting training in power system operation and allied areas. It facilitates the dispatcher to be trained in normal, emergency and restorative conditions. A numerically stable algorithm that can accommodate larger time step width will be an ideal choice for DTS, but it should also have smaller time step width to capture short term dynamics. Hence, an algorithm has been developed, for simulation of long-term dynamics at a ‘larger time step width’, in order to decrease the total simulation time while the simulation is made to run for a 24 hour system load curve and also to capture the short term dynamics with a ‘small time step width’. To these authors’ knowledge the approach used in this algorithm has not been used elsewhere. This article presents the modelling and simulation of a variable step size algorithm for a DTS. Long-term dynamics gives an observable system response, which can be used to train system operators. Short-term dynamics gives the transient stability of the system. An efficient Network Topology Processor and apt component models were interfaced with this algorithm. This algorithm has been implemented in a DTS - Power System Simulation Module and tested for many possible cases like, Bus fault application and removal, Line opening and closing, etc.

Upgrades to the ATLAS Level-1 Calorimeter Trigger

In 2015 the Large Hadron Collider will run with increased center-of-mass energy and luminosity. To maintain a high efficiency in selecting interesting collisions for the physics analyses in the next data-taking period, event topology information will be added to the ATLAS Level-1 real time data path and processed by a new Topology Processor (L1Topo). To cope with the luminosity levels foreseen after the 2018 LHC upgrade, a new digital trigger path for the Liquid Argon calorimeters will provide finer granularity and depth segmentation in the electromagnetic layer to new Level-1 feature extractors (FEX) for an improved electron, photon, tau and jet selection. We present the ongoing and future calorimeter trigger upgrades to the ATLAS Level-1 trigger.

An efficient automated topology processor for state estimation of power transmission networks

A robust network topology processor that can be utilized in both traditional and PMU-based state estimators is developed. Previous works in the field of topology processing are scrutinized and their drawbacks are identified. Building on top of the state of the art, an algorithm covering the limitations of available topology processing approaches and including new features is proposed. The presented algorithm was implemented in MATLAB and tested using two different power networks with detailed substation configurations (bus/breaker models) including a modified version of the IEEE Reliability Test System 1996. As the topology processor is intended to supply network topologies to a PMU-based Sate Estimator, the IEEE Reliability Test System 1996 is simulated in real-time using the eMegaSim Opal-RT real-time simulator which is part of “SmarTS Lab” at KTH Royal Institute of Technology. Testing is carried out through several test scenarios and computation times are calculated. It is shown that the computation times are adequate for supporting a PMU-only state estimator.

A multiagent-based distribution automation system for service restoration of fault contingencies

Distribution automation system agents (DASAs) are developed to enhance customer service restoration for the fault contingencies of distribution systems. A multiagent system (MAS) integrates topology processor information and the current loadings of service zones with distribution feeders and the main transformers in substations to derive the proper restoration plan after the faulted location has been identified and isolated. The heuristic rules based on the standard operation procedures of Taiwan Power Company's distribution system are included in the best first search of the MAS to ensure the restoration plan derived complies with operation regulations. When the capacity reserves of supporting feeders and main transformers are not sufficient to cover the fault restoration of the fault contingency during summer peak season, the load shedding scheme is determined by the MAS to restore service to as many key customers and loads as possible by considering the service priority of each service zone of the distribution feeders. A Taiwan Power Company (Taipower) distribution system with 35 feeders is selected for computer simulation to demonstrate the effectiveness of the proposed methodology to devise a service restoration plan for the distribution fault contingency. Copyright © 2010 John Wiley & Sons, Ltd.

Line outage contingency analysis including the system islanding scenario

The paper describes an algorithm for determining the line outage contingency of a line taking into account of line over load effect in remaining lines and subsequent tripping of over loaded line(s) leading to possible system split or islanding of a power system. The optimally ordered sparse [ B′], [ B″] matrices for the integrated system are used for load flow analysis to determine modified values of voltage phase angles [ δ] and bus voltages [ V] to determine the over loading effect on the remaining lines due to outage of a selected line outage contingency. In case of over loading in remaining line(s), the over loaded lines are removed from the system and a topology processor is used to find the islands. A fast decoupled load flow (FDLF) analysis is carried out for finding out the system variables for the islanded (or single island) system by incorporating appropriate modification in the [ B′] and [ B″] matrices of the integrated system. Line outage indices based on line overload, loss of load, loss of generation and static voltage stability are computed to indicate severity of a line outage of a selected line.

Dynamic topology processing in a radial distribution system

A dynamic topology processor for a radial distribution system using object-oriented methodology is presented. The potential of object-oriented design patterns is also employed to obtain an extendible design. The decorator design pattern is used to separate the topology-based attributes from the attributes representing physical characteristics of the objects. Using decorator pattern, responsibilities can be dynamically attached to or removed from the objects. The state design pattern is used to model the switching states of the tie and sectionalising switches. The proposed topology-processor algorithm is a local updating technique, hence less time consuming. The proposed algorithm has been implemented in C++ and tested with a modified 69-bus system. It has been found that the average CPU time required to modify the links between the objects following a switching operation is only 0.4 ms.

Web tool opens up power system visualization

This article presents a flexible architecture of a Web-based tool that serves as a platform for power system visualization with open data structures. Different from regular applications, this platform may be viewed as a semicompleted application. It implements common features of a power system application such as GIS-like drawing and visualization, built-in topology processor, and so on. Meanwhile, the platform defines open data structures for system components with the consideration of efficiency and flexibility. It also provides a mechanism to link itself with external engines, instead of implementing the engines directly. This architecture may achieve considerable flexibility. For instance, users may extend and customize data structures of power system components. Users may also develop their own analytic engines based on their specific needs and link them with the platform. To maximize the benefits to users, the proposed platform is Web-enabled with Java client-side technology. It is universally accessible, instantaneously upgradable, and operating-system independent.

Data structure for radial distribution system load flow analysis

Owing to the radial nature and high R/X ratio, radial distribution systems (RDS) employ a special recursive technique for distribution load flow (DLF). An efficient method for DLF plays a critical role in automation algorithms of RDS whose scope encompasses fault isolation, network reconfiguration and service restoration. The ability of automation algorithms to handle these complex tasks that require frequent topology changes in the RDS demands a dynamic topology processor based on a well-defined data structure. The purpose of this paper is to formulate a dynamic data structure (DDS) and an algorithm that generates the DDS of the RDS as an R-tree. The proposed DDS algorithm generates the DDS and is used as a topology processor in the DLF algorithm. The resulting DLF algorithm is computationally efficient and can handle rapidly changing topology by updating the R-tree. The pseudocodes for the DDS algorithm and the overall recursive algorithm for DLF are presented. Various RDS have been tested with the proposed method and the results demonstrate its efficiency over other known methods of DLF.

An AI-based automatic power network topology processor

This paper describes a new power network topology processor which has been successfully used in two practical power system application programs. Artificial intelligence (AI) techniques have been used and this provides several advantages. AI's frame representation method is used to represent electric network configuration. This avoids manual numbering on a large amount of circuit breaker terminals/circuits. Rule-based method has been adopted for substation's bus configuration analysis instead of the search method. This makes the analysis simple and adaptable to new types of bus configurations just by adding corresponding rules. AI's search techniques have been applied for network graph search making the search algorithm simpler and easier to be programmed. Some results from the application of the proposed topology processor are also included in the paper.

Object-oriented network topology processor [power system automation

Modern power systems have grown both in size and complexity. Various constraints, such as security, economy and environmental regulations, are forcing power systems to operate closer to their design capabilities and security margins. Here, the authors describe a system where a network topology processor groups physical buses at the substation into electrical buses, builds connectivity from electrical buses to the network branches, and analyzes electrical network connectivity for islands.

A topology-based algorithm for tracking network connectivity

This paper describes a fast algorithm to track the network connectivity of islands, currently in production as part of AEP's new network topology processor function. After breaker activities have caused one or more branches to switch buses, the new algorithm uses a local updating procedure to track the network connectivity. This is in contrast to the global depth-first search method currently used in most energy management system installations. The new algorithm and its two subordinate tasks are introduced and thoroughly discussed. The corresponding data structures are also described to aid implementation by other investigators. An example is provided to illustrate the algorithmic steps. The results of applying the new algorithm to a 2450-bus, 5600-branch AEP real-time base-case network are presented. Graph theory notation and terminology are used throughout.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Detection of Topology Errors by State Estimation

In modern energy management systems (EMS), there are two types of measurement data collected by the SCADA (supervisory control and data acquisition) system, namely, status data of breakers and switches, and analog data of real and reactive power flows, injections, and bus voltages. The status data are used to determine real-time topology of the network. The analog data are used to determine line and transformer loading and voltage profile. These data are noisy due to measurement errors, communication noise, missing data, etc. In addition to simple checking of the analog data locally, in most modern EMS, state estimation is used to process these data globally to correct errors in the raw analog measurement data. In this paper, the use of global information in state estimation to correct errors in the direct measurements of the status data is proposed and conditions for detectability of errors are analyzed. The telemetered data of breaker and switch status are processed in the EMS computer to determine the present network topology of the system, and this function is called network topology processor. Errors in status data will show up as errors in the network topology. Sasson et al and Dy Liacco et al used a tree search algorithm for the network topology processor. The method is widely used in practice. Bonanomi et al proposed a sequential search method through the network graph. Recently Lugtu et al suggested the approach of using state estimation results for topology error detection.