Phillip M. Ashton

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.

Parallel detrended fluctuation analysis for fast event detection on massive PMU data

Phasor measurement units (PMUs) are being rapidly deployed in power grids due to their high sampling rates and synchronized measurements. The devices high data reporting rates present major computational challenges in the requirement to process potentially massive volumes of data, in addition to new issues surrounding data storage. Fast algorithms capable of processing massive volumes of data are now required in the field of power systems. This paper presents a novel parallel detrended fluctuation analysis (PDFA) approach for fast event detection on massive volumes of PMU data, taking advantage of a cluster computing platform. The PDFA algorithm is evaluated using data from installed PMUs on the transmission system of Great Britain from the aspects of speedup, scalability, and accuracy. The speedup of the PDFA in computation is initially analyzed through Amdahls Law. A revision to the law is then proposed, suggesting enhancements to its capability to analyze the performance gain in computation when parallelizing data intensive applications in a cluster computing environment.

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.

Big data analytics on PMU measurements

Phasor Measurement Units (PMUs) are being rapidly deployed in power grids due to their high sampling rates. PMUs offer a more current and accurate visibility of the power grids than traditional SCADA systems. However, the high sampling rates of PMUs bring in two major challenges that need to be addressed to fully benefit from these PMU measurements. On one hand, any transient events captured in the PMU measurements can negatively impact the performance of steady state analysis. On the other hand, processing the high volumes of PMU data in a timely manner poses another challenge in computation. This paper presents PDFA, a parallel detrended fluctuation analysis approach for fast detection of transient events on massive PMU measurements utilizing a computer cluster. The performance of PDFA is evaluated from the aspects of speedup, scalability and accuracy in comparison with the standalone DFA approach.

Implementation of Wide Area Monitoring Systems and laboratory-based deployment of PMUs

Power systems are operating in a more complicated condition and therefore encounter more challenges. If one part of a power grid becomes seriously out of synchronism with the rest, the whole network can become unstable and blackout may occur. In this regard, we need to use advanced and smart monitoring tools to quickly and reliably observe the changing state of the key electrical parameters in real time, take appropriate corrective measures and isolate faults. Phasor Measurement Units (PMUs) by employing satellite technology, offer a state-of-the-art Wide Area Monitoring System (WAMS) for improving power system monitoring, control and protection. In this paper, we present information about WAMS components and requirements as well as description of work carried out in Brunel University laboratory to develop and implement a synchronized measurement system.

Investigation of open standards to enable interoperable wide area monitoring for transmission systems

Nowadays, power systems face more challenging network wide issues with regard to ensuring secure and reliable operation. Therefore, having a wide area monitoring system is a vital need in order to detect problems and react on them as quickly as possible. An important component when providing wide area monitoring and control for transmission networks is the SCADA system, which connects the substations to the control center by polling data from Remote Terminal Units (RTUs). However, due to data rate limitations, the monitoring is relatively static and therefore infrequent. By using Phasor Measurement Units (PMUs) data can be provided in higher rates and with higher accuracy. Since different manufacturers exist in the market, standardization is the key for advancement of the connectivity and interoperability within the system. In the past, utilities used to employ proprietary protocols, which were specified by the product vendors. Gradually, it was decided to move towards open standards to provide an interoperable environment and improve modelling capabilities. Apart from PMU standards, in a typical power system several communication protocols exist and are required for transferring data and each of them covering certain domains and specific groups of data. The objective of this paper is to investigate the adoption, development and performance of the most common open standards to enable interoperable wide area monitoring systems.

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.