Tie-line modelling in interconnected synchrophasor network for monitoring grid observability, cyber intrusion and reliability

The incorporation of a tie-line between two areas may be beneficial in two ways. First, the reserve capacity of the assisting area support to the assisted area, and second, the number of Phasor Measurement Unit (PMU) requirements will become smaller for complete observability of the interconnected grid. The objective function is formulated to integrate the observability and reliability analysis for the two interconnected synchrophasor networks. The effect of Zero Injection Bus (ZIB) is included in the observability constraints to reduce the number of PMUs deployed in the system. The number of optimal PMU deployments will be greater for two interconnected systems in comparison with a single area. Therefore, interconnected systems become more vulnerable to cyber risk. The paper discusses the cumulative analysis of system observability and reliability during an anomaly situation that occurs with a PMU device due to a cyber-attack. The reliability indices Interconnected System Load Interruption Probability (ISLIP) and Interconnected System Demand Not Supplied (ISDNS) are evaluated when an anomaly occurs with optimally deployed PMU in the network by including and excluding the effect of ZIB. By doing so, the most reliable location for PMU deployment can be obtained for both the area. Reliability Test System (RTS)-24 bus is used for each area to modify the test system by incorporating tie-lines between them

Minimum Sparsity of Unobservable Power Network Attacks

Physical security of power networks under power injection attacks that alter generation and loads is studied. The system operator employs Phasor Measurement Units (PMUs) for detecting such attacks, while attackers devise attacks that are unobservable by such PMU networks. It is shown that, given the PMU locations, the solution to finding the sparsest unobservable attacks has a simple form with probability one, namely, $\kappa(G^M) + 1$, where $\kappa(G^M)$ is defined as the vulnerable vertex connectivity of an augmented graph. The constructive proof allows one to find the entire set of the sparsest unobservable attacks in polynomial time. Furthermore, a notion of the potential impact of unobservable attacks is introduced. With optimized PMU deployment, the sparsest unobservable attacks and their potential impact as functions of the number of PMUs are evaluated numerically for the IEEE 30, 57, 118 and 300-bus systems and the Polish 2383, 2737 and 3012-bus systems. It is observed that, as more PMUs are added, the maximum potential impact among all the sparsest unobservable attacks drops quickly until it reaches the minimum sparsity.Comment: submitted to IEEE Transactions on Automatic Contro

Visualization And Mining Of Phasor Data From Optimally Placed Synchrophasors In A Smart-Grid

Synchrophasors, or also known as Phasor Measurement Units (PMUs), are the state- of-the-art measurement sensor that gather key sensor parameters such as voltage, frequency (f), current (i), and phase angle (ϕ) to monitor the state of an electric grid. The significant feature of a synchrophasor is in its ability to provide real-time streaming data from smart grid. The sampling rate of PMUs ranges from 30 samples to a maximum of 120 samples per second. With such large date-rate, the operations of the power-grid is known with high granularity. However, utilities face certain challenges with synchrophasor measurements. One of the common challenge with synchrophasor is the selection of location to place them in the grid. A synchrophasor placed on a bus is capable of measuring currents, voltages, phasor and frequency information on the entire transmission line incident to that bus. Furthermore, neighboring buses also become observable (i.e. adjacent bus voltage equations are solvable) using Ohm’s law, Kirchhoff’s Voltage Law (KVL) and Kirchhoff’s Current Law (KCL). Thus, it is not necessary to place PMUs on every single bus of the power-grid. Synchrophasors are expensive units and depending on vendor type, the number of measurement channels and features, the cost per unit can increase. There are several optimal solutions proposed to minimize the cost function to place the synchrophasors. Studies often ignored other metrics such as reliability, and security. This can jeopardize the reliability of the power-grid. Thus, this thesis work focus on a multi-objective problem that include reliability, cost, energy, and distance. This research proposes a criteria called as Optimal Redundancy Criterion (ORC) based on Linear Programming (LP) methods to find an optimal solution for the placement problem. Although, synchrophasors provide real-time information about the grid, the system operators need to identify, classify and analyze fault or anomalies in the power-grid. Such detection of the faults will improve the situational awareness of the power-grid. This research addresses such challenges by developing data mining algorithms for effective visualization and control of data. The secondary goal is accomplished by implementing a Density-Based Spatial Clustering of Applications with Noise (DBSCAN) algorithm to IEEE test system and phasor data from openPDC framework. The scalability and decision making process for large scale utility test systems using DBSCAN is also investigated

Optimal Placement of Phasor Measurement Units for Power Systems Using Genetic Algorithm

Power grids require monitoring to operate with high efficiency while minimizing the chances of having a failure. However, current monitoring scheme which consists of SCADA (Supervisory Control and Data Acquisition), accompanied with conventional meters distributed throughout the grid, is no longer sufficient to maintain an acceptable operation of the grid. This is evident from the multiple failures and blackouts that happened and are still happening in grids worldwide. This issue became more severe due to systems being operated near their limits (to reduce costs and due to the increase in electricity demands), as well as, the addition of renewable energy sources, which usually have abrupt changes. Smart grids were introduced as a solution to this issue by the inclusion of Wide Area Monitoring System (WAMS), which is mainly based on Phasor Measurement Units (PMU), which are measurement devices that provides synchronized time stamped measurements with high sending rate which significantly improves the monitoring of the grid. However, PMUs are relatively expensive (considering both direct and indirect costs incurred). Thus, it is desired to know the minimum number of PMUs required for achieving certain monitoring criteria. Thus, Optimal PMU Placement (OPP) formulates an optimization problem to solve this issue. In the literature of OPP, multiple objectives and constraints are considered, based on desired criteria. In this thesis, a review of OPP is made, followed by the application of selected algorithms (Integer Linear Programming and Genetic Algorithm) on various test systems as a verification and then applying it to Qatar Grid, to compare between different considerations as well as gain insight about the possible PMU placements for Qatar Grid. The contribution of this thesis is introducing a modified fitness function for the Genetic Algorithm that provides more diverse results than previous papers, while incorporating for various considerations like Zero Injection Buses, Conventional Measurements and current branch limit. It also analyzes the results of current branch limit and provides new plots describing their effects

Optimal placement of phasor measurement units using the Advanced Matrix Manipulation algorithm

Includes abstract.Includes bibliographical references.This thesis investigates the problem of the Optimal Placement scheme of Phasor Measurement Units in electrical power systems for State Estimation to facilitate improved monitoring and control of the system parameters. The research work done for this thesis begins with review of Supervisory Control and Data Acquisition systems (SCADA). SCADA-based systems are currently employed for condition monitoring and control of industrial and utility electrical power systems. For utility power networks, the main problem with voltage and current phasor data captured by SCADA systems is that they are not synchronised with respect to each other in a present-time or Real-time framework. This implies that both magnitude and phase angle of the measured phasors tend to get affected by slow data flow provided by SCADA to the points of utilization and also by differences in time instants of data capture. These factors inhibit theefficiency and quality of the power system monitoring and control. “Phasor Measurement Unit” (PMU) is a relatively new technology that, when employed in power networks, offers real-time synchronised measurements of the voltages at buses and currents along the lines that connect them. This is accomplished by using a GPS based monitoring system which facilitates time synchronisation of measurements and unlike SCADA, makes the measured data available in Real-Time format. SCADA is not able to provide Real-time data due to the low speeds at which RTUs (Remote Terminal Units) provide data. Availability of time-stamped phasor measurements makes PMUs preferable for power system monitoring and control applications such as State Estimation, Instability Prediction Analysis, Real-time Monitoring of the system conditions, Islanding Detection, System Restoration and Bad Data Detection