Wide-Area Backup Protection Against Asymmetrical Faults Using Available Phasor Measurements

This paper proposes a robust and computationally efficient wide-area backup protection (WABP) scheme against asymmetrical faults on transmission systems using available synchronized/unsynchronized phasor measurements. Based on the substitution theorem, the proposed scheme replaces the faulted line with two suitable current sources. This results in a linear system of equations for WABP, with no need of full system observability by measurement devices. The identification of the faulted line is attributed to the sum of squared residuals (SoSR) of the developed system of equations. To preserve accuracy, the scheme limits the calculations to the assessment of the negative-sequence circuit of the gird. Relevant practical aspects that have not been properly addressed in the literature, namely the non-simultaneous opening of circuit breakers (CBs) and their single-pole tripping for single-phase to ground faults are investigated. The linearity of the formulations derived removes concerns over convergence speed and potential time-synchronization challenges. The proposed scheme is able to identify the faulted line and retain this capability for hundreds of milliseconds following the fault inception. More than 20 000 simulations conducted on the IEEE 39-bus test system verify the effectiveness of the proposed WABP scheme

Vulnerability analysis of satellite-based synchronized smart grids monitoring systems

The large-scale deployment of wide-area monitoring systems could play a strategic role in supporting the evolution of traditional power systems toward smarter and self-healing grids. The correct operation of these synchronized monitoring systems requires a common and accurate timing reference usually provided by a satellite-based global positioning system. Although these satellites signals provide timing accuracy that easily exceeds the needs of the power industry, they are extremely vulnerable to radio frequency interference. Consequently, a comprehensive analysis aimed at identifying their potential vulnerabilities is of paramount importance for correct and safe wide-area monitoring system operation. Armed with such a vision, this article presents and discusses the results of an experimental analysis aimed at characterizing the vulnerability of global positioning system based wide-area monitoring systems to external interferences. The article outlines the potential strategies that could be adopted to protect global positioning system receivers from external cyber-attacks and proposes decentralized defense strategies based on self-organizing sensor networks aimed at assuring correct time synchronization in the presence of external attacks

Backup protection requirements in future low-inertia power systems

The content of this paper will illustrate how, in the future, the power transmission system in Great Britain (GB) may be much "weaker" than it is at present, and will describe the potential impact that this could have on the voltage profiles during faults, and how the operation of backup protection system operation, if required, needs to be considered carefully to ensure system integrity in the future. The potential for future problems associated with generators’, converter-interfaced infeeds’, and HVDC interconnectors’ potential inability to “ride through” during slow/backup protection operations, and the consequent risk of complete system collapse, will also be highlighted. The paper also contains a description of ongoing and future work concerned with investigation of the use of wide-area communications systems, which may already be in existence and used for other purposes, to enhance backup protection performance and possibly offer an alternative and improved solution compared with existing schemes. It is shown how such a system could potentially be "settings-free" and establish and maintain an image of the connectivity of the network from either SCADA data and/or analysing current flows during normal operation. Example results of simulations are included to demonstrate the concept of identifying fault locations and protection failures using measured voltages from phasor measurement units (PMUs). This may act as a foundation for a future backup protection scheme and this is discussed in the conclusions and future work sections

Development of cost-effective phasor measurement unit for wide area monitoring system applications

Sustained growth in the demand with unprecedented investments in the transmission infrastructure resulted in narrow operational margins for power system operators across the globe. As a result, power networks are operating near to stability limits. This has demanded the electrical utilities to explore new avenues for control and protection of wide area systems. Present supervisory control and data acquisition/energy management systems (SCADA/EMS) can only facilitate steady state model of the network, whereas synchrophasor measurements with GPS time stamp from wide area can provide dynamic view of power grid that enables supervision, and protection of power network and allow the operator to take necessary control/remedial measures in the new regime of grid operations. Construction of phasor measurement unit (PMU) that provide synchrophasors for the assessment of system state is widely accepted as an essential component for the successful execution of wide area monitoring system (WAMS) applications. Commercial PMUs comes with many constraints such as cost, proprietary hardware designs and software. All these constraints have limited the deployment of PMUs at high voltage transmission systems alone. This paper addresses the issues by developing a cost-effective PMU with open-source hardware, which can be easily modified as per the requirements of the applications. The proposed device is tested with IEEE standards

PMU-Based Adaptive Central Protection Unit (CPU) for Power Systems with High DG Penetration

The rapid expansion and integration of Distributed Generations (DG) into power systems plays an increasingly important role in their planning, operation, and control. The rules used to design and operate current systems are being altered by the DGs incorporation. This may jeopardize the system\u27s reliability and security. Private owners of large DGs should not be restricted to a particular time schedule to connect/disconnect their generation to/from the system. This feature dynamically changes the typical power system with unidirectional power flow from generation to the loads. A smart Central Protection Unit (CPU) is needed to take proper measures in case of DGs arbitrarily disconnection, isolation or any other type of fault. On the other hand, recent major blackouts resulting from pushing the power systems to the edge has revealed the need for a smarter supervisory system for enhanced reliability and stability. Hence, there is a high demand for a robust and smart supervisory system which can diagnose power systems disturbances in real-time and prevent aggravation and expansion.This thesis is focused on studying the impacts of DG integration on the power systems. Phasor Measurement Units (PMUs) play an important role on the monitoring of power systems. Multiple major data analysis techniques including K-means, Smart K-means clustering, and DBSCAN clustering of the PMU output data have been implemented. Higher order moments of Kurtosis and Skewness indices were also employed in order to estimate the system state

Wide-Area Synchrophasor Data Server System and Data Analytics Platform

As synchrophasor data start to play a significant role in power system operation and dynamic study, data processing and data analysis capability are critical to Wide-area measurement systems (WAMS). The Frequency Monitoring Network (FNET/GridEye) is a WAMS network that collects data from hundreds of Frequency Disturbance Recorders (FDRs) at the distribution level. The previous FNET/GridEye data center is limited by its data storage capability and computation power. Targeting scalability, extensibility, concurrency and robustness, a distributed data analytics platform is proposed to process large volume, high velocity dataset. A variety of real-time and non-real-time synchrophasor data analytics applications are hosted by this platform. The computation load is shared with balance by multiple nodes of the analytics cluster, and big data analytics tools such as Apache Spark are adopted to manage large volume data and to boost the data processing speed. Multiple power system disturbance detection and analysis applications are redesigned to take advantage of this platform. Data quality and data security are monitored in real-time. Future data analytics applications can be easily developed and plugged into the system with simple configuration

Performance Improvement of Wide-Area-Monitoring-System (WAMS) and Applications Development

Wide area monitoring system (WAMS), as an application of situation awareness, provides essential information for power system monitoring, planning, operation, and control. To fully utilize WAMS in smart grid, it is important to investigate and improve its performance, and develop advanced applications based on the data from WAMS. In this dissertation, the work on improving the WAMS performance and developing advanced applications are introduced.To improve the performance of WAMS, the work includes investigation of the impacts of measurement error and the requirements of system based on WAMS, and the solutions. PMU is one of the main sensors for WAMS. The phasor and frequency estimation algorithms implemented highly influence the performance of PMUs, and therefore the WAMS. The algorithms of PMUs are reviewed in Chapter 2. To understand how the errors impact WAMS application, different applications are investigated in Chapter 3, and their requirements of accuracy are given. In chapter 4, the error model of PMUs are developed, regarding different parameters of input signals and PMU operation conditions. The factors influence of accuracy of PMUs are analyzed in Chapter 5, including both internal and external error sources. Specifically, the impacts of increase renewables are analyzed. Based on the analysis above, a novel PMU is developed in Chapter 6, including algorithm and realization. This PMU is able to provide high accurate and fast responding measurements during both steady and dynamic state. It is potential to improve the performance of WAMS. To improve the interoperability, the C37.118.2 based data communication protocol is curtailed and realized for single-phase distribution-level PMUs, which are presented in Chapter 7.WAMS-based applications are developed and introduced in Chapter 8-10. The first application is to use the spatial and temporal characterization of power system frequency for data authentication, location estimation and the detection of cyber-attack. The second application is to detect the GPS attack on the synchronized time interval. The third application is to detect the geomagnetically induced currents (GIC) resulted from GMD and EMP-E3. These applications, benefited from the novel PMU proposed in Chapter 6, can be used to enhance the security and robust of power system