A. M. Carter

Comparison of Three Electromechanical Oscillation Damping Estimation Methods

This paper describes three data driven methods to monitor electromechanical oscillations in interconnected power system operation. The objective is to compare and contrast the performance of the methods. The accuracy of damping ratio and frequency of oscillations are the measures of the performance of the algorithms. The advantages and disadvantages of various techniques and their limitations to measurement noise have been considered while assessing performance. The target frequency and damping are computed using the Nordic power system simulation model.

Novel application of detrended fluctuation analysis for state estimation using synchrophasor measurements

The phasor measurement unit (PMU), with its ability to directly calculate synchronized positive sequence voltages and currents (magnitude and phase), offers a more current and accurate view of the power system compared to that provided by traditional measurements and state estimation (SE). However, the high-resolution data, provided at rates of 50 Hz and 60 Hz (dependant on nominal frequency), capture any transient or dynamic events occurring on the network, potentially distorting the intended steady-state view at various points of the power system. In this paper we propose the use of detrended fluctuation analysis (DFA) to detect and isolate such events for alternative investigation. Comparisons are made between the state estimator and installed PMUs on the high-voltage transmission system of Great Britain.

Inertia Estimation of the GB Power System Using Synchrophasor Measurements

A novel procedure for estimating the total inertia of the Great Britain (GB) power system is presented. Following an instantaneous in-feed loss, regional variations in the estimate of inertia are obtained from measured frequency transients using installed synchronised phasor measurement units (PMUs). A method is proposed to first detect a suitable event for analysis, and then filter the measured transients in order to obtain a reliable estimate of inertia for a given region of the GB network. The total inertia for the whole system is then calculated as a summation, with an estimate also provided as to the contribution to inertia from residual sources, namely synchronously connected demand and embedded generation. The approach is first demonstrated on the full dynamic model of the GB transmission system, before results are presented from analyzing the impact of a number of instantaneous transmission in-feed loss events using phase-angle data provided by PMUs from the GB transmission network and also devices installed at the domestic supply at 4 GB universities.

Application of phasor measurement units to estimate power system inertial frequency response

The inherent reduction in inertial frequency response resulting from a shift in generation mix towards renewables, is presenting a range of operational planning challenges for transmission system operators (TSOs) globally. Dictating the ability to maintain frequency following significant mismatches in supply and demand, it is of great consequence to the real-time operation of the power system. In this paper we discuss the estimation of system inertia constant using synchronised data, provided by installed phasor measurement units (PMUs). Results are presented from analysing the impact of over 50 transmission system events that were observed on the electricity transmission network of Great Britain.

Prospective Wide Area Monitoring of the Great Britain Transmission System using Phasor Measurement Units

National Grid, the Transmission System Operator for Great Britain, has recently installed a Wide Area Monitoring System (WAMS), to improve the real-time view of the power system. Phasor Measurement Units (PMUs) have been installed, primarily through upgrades to digital fault recorders, as an extension to dynamic system monitoring. This paper reviews the development of WAMS on the GB System and presents the experiences so far, detailing both existing and future applications of synchrophasor technology, such as oscillation analysis, model validation and improved situational awareness.

Information standards to support application and enterprise interoperability for the smart grid

Current changes in the European electricity industry are driven by regulatory directives to reduce greenhouse gas emissions, at the same time as replacing aged infrastructure and maintaining energy security. There is a wide acceptance of the requirement for smarter grids to support such changes and accommodate variable injections from renewable energy sources. However the design templates are still emerging to manage the level of information required to meet challenges such as balancing, planning and market dynamics under this new paradigm. While secure and scalable cloud computing architectures may contribute to supporting the informatics challenges of the smart grid, this paper focuses on the essential need for business alignment with standardised information models such as the IEC Common Information Model (CIM), to leverage data value and control system interoperability. In this paper we present details of use cases being considered by National Grid, the GB transmission system operator for information interoperability in pan-network system management and planning.

Foundations of a Metamodel Repository for Use With the IEC Common Information Model

The development of the smart grid calls for enhanced power system application interoperability and knowledge management. The IEC Common Information Model (CIM) supports semantic interoperability but multiple identities attributed to common power system resources present challenges to unambiguous metadata model merging within a repository. This paper describes an original methodology for the building of a novel metadata model repository that concentrates our knowledge of enterprise power system resources. We leverage the value of model namespaces and resource description framework (RDF) technology in providing contexts for multiple identities referring to common power system resources. This novel approach aims to develop a more realistic understanding of network reality than repositories depending on a single CIM XML namespace and contributes to engineering an “enterprise ontology” supporting interoperability and business intelligence. We demonstrate this novel approach with reference to National Grid use cases for network operation and planning model management roles.

Smart grid interoperability use cases for extending electricity storage modeling within the IEC Common Information Model

The IEC Common Information Model (CIM) is recognized as a core standard, supporting electricity transmission system interoperability. Packages of UML classes make up its domain ontology to enable a standardised abstraction of network topology and proprietary power system models. Since the early days of its design, the CIM has grown to reflect the widening scope and detail of utility information use cases as the desire to interoperate between a greater number of systems has increased. The cyber-physical nature of the smart grid places even greater demand upon the CIM to model future scenarios for power system operation and management that are starting to arise. Recent developments of modern electricity networks have begun to implement electricity storage (ES) technologies to provide ancillary balancing services, useful to grid integration of large-scale renewable energy systems. In response to this we investigate modeling of grid-scale electricity storage, by drawing on information use cases for future smart grid operational scenarios at National Grid, the GB Transmission System Operator. We find current structures within the CIM do not accommodate the informational requirements associated with novel ES systems and propose extensions to address this requirement.

Transient event detection and analysis of the GB transmission system using synchrophasor measurements

The inclusion of Phasor Measurement Units (PMUs) to the electricity network of Great Britain is providing insight beyond the steady state, into the behaviour of the power system. Synchronised measurements, from a fair geographical distribution of devices are allowing the regional differences, following transient events, to be examined. This is forcing revision of the previous assumption of network-wide behaviour. In this paper a number of transmission level incidents, detected by two independent wide area monitoring systems (WAMS), installed at both the transmission level and domestic supply, have been analysed, with a focus on the events impact to different areas of the grid. The analysis identifies the seemingly obvious impact to voltage magnitude but also the regional variation in frequency, df/dt and hence system inertia.

Potential integration of Phasor Measurement Units and Wide Area Monitoring Systems based upon National Grid enterprise level CIM

Summary form only given. The IEC Common Information Model (CIM) supports interoperability between power system applications by providing, as a reference model, a generic means of sharing heterogeneous proprietary data models at an enterprise level. Extension of the CIM to facilitate the modelling of Intelligent Electronic Devices (IEDs) such as Phasor Measurement Units (PMUs) is desirable from the perspective of data integration and wider uses of situational awareness. Such use cases could include near real time update of the Energy Management System (EMS) and advanced visualization of network status. However, the unification or harmonization of two key standards will be required in order to achieve such a goal. IEC 61970, a core CIM standard, was developed in (Universal Modelling Language) UML to facilitate the interoperability of extensive power system applications. Independently, IEC 61850 was developed primarily for substation control, monitoring and automation purposes and therefore represents a significant part of the Wide Area Monitoring Systems (WAMS) and PMUs domain. This presentation provides a brief overview of both standards and potential ways in which they can be extended to interoperate for the purpose of modeling IEDs and PMUs. Current enterprise level CIM use cases relating to National Grid as the GB transmission system operator will also be presented.