Mert Korkali

Placement of PMUs with channel limits

Synchronized phasor measurements are changing the way power systems are monitored and operated. Their efficient incorporation into various applications which are executed in energy management control centers, require strategic placement of these devices. Earlier studies which consider placement of PMUs to be used for state estimation, assume that these devices will have unlimited channel capacities to record as many phase voltages and currents as needed. However, all existing PMUs come with a limited number of channels and their costs vary accordingly. In this study, a revised formulation of the placement problem and its associated solution algorithm will be presented. Examples will be used to illustrate the impact of having limited number of channels on the location and number of required PMUs to make the system observable. Developed methods will take into account existing injections measurements, in particular the virtual measurements such as zero injections that are available at no cost at electrically passive buses.

Traveling-Wave-Based Fault-Location Technique for Transmission Grids Via Wide-Area Synchronized Voltage Measurements

This paper delineates a novel analytical and computational approach to fault location for power transmission grids. The proposed methodology involves an online and an offline stage. The online stage is based solely on the utilization of the time-of-arrival (ToA) measurements of traveling waves propagating from the fault-occurrence point to synchronized wide-area monitoring devices installed at strategically selected substations. The captured waveforms are processed together at the time of fault in order to identify the location of the fault under study. The overall performance of the developed technique is demonstrated using Alternative Transients Program (ATP) simulations of fault transients and postprocessing the faulted waveform data via discrete wavelet transform. The applicability of the algorithm is independent of the fault type and can readily be extended to transmission grids of any size.

Optimal Deployment of Wide-Area Synchronized Measurements for Fault-Location Observability

This paper considers the problem of strategically placing a minimum number of synchronized measurements in a transmission system so that faults can be detected and identified irrespective of their locations. The proposed solution is based on a fault-location method which was developed and documented in an earlier paper by the authors. Hence, it is intended as an extension of the previous work to facilitate its efficient implementation via optimal sensor placement. The paper will first provide a brief review of the fault-location method and will then describe the optimal deployment scheme for placing synchronized voltage sensors in the transmission system. Simulated fault transients by an electromagnetic transients simulation program will be used to illustrate the performance of the developed technique.

Impact of network sparsity on strategic placement of phasor measurement units with fixed channel capacity

This paper investigates the optimal placement of synchronized phasor measurement units (PMU) in order to fully observe a given power system. Optimal placement methods to account for contingencies, loss of measurements as well as existing conventional measurements and zero injections have already been presented in previous publications. What differentiates this study from those already reported in the literature is the fact that it accounts for the number of available channels for the chosen type of PMU. This is shown to be a critical factor in strategic placement of these devices. Furthermore, it is also demonstrated that depending upon the topology of the network, there will be an upper limit on the number of channels for the PMUs beyond which installation costs will not be reduced any further. Results of applying the developed optimization method to systems with different sizes and topologies are presented. The results of this study will be more useful as the number of PMU installations increase to levels that will make the system fully observable based solely on PMUs with different number of channel capacities.

Robust Fault Location Using Least-Absolute-Value Estimator

This paper presents a robust alternative to the previously developed method to reliably locate power-system faults using simultaneously recorded data from multiple locations. Automatic removal of corrupted measurements resulting from various factors (e.g., sensor breakdowns and cyberattacks) will be accomplished via the use of a least-absolute-value (LAV) estimator for fault location. Furthermore, inherent limitations of the approach imposed by sensor configurations as well as the effect of quantization errors incurred by low-precision sensors on the accuracy of estimated fault locations will be described. The performance of the overall algorithm will be tested and verified by fault scenarios on the IEEE 118-bus transmission grid.

Fault location in meshed power networks using synchronized measurements

This paper introduces a new fault location algorithm for interconnected power networks established upon the differences of arrival times of traveling waves arriving at sparsely located synchronized recorders on any bus in the network. The performance validation of the developed method is done through an implementation on the IEEE 14-bus system by using ATP/EMTP program in collaboration with MATLAB Wavelet Toolbox.

Reliable measurement design against loss of PMUs with variable number of channels

Phasor measurement units (PMU) are rapidly populating the substations and enabling improvements for various network applications, one of which is the state estimator. Installation of large numbers of PMUs which may be required for network observability must be preceeded by a detailed analysis of optimal location and type of these devices. Since PMUs may have different number of channels depending on the manufacturer and model type, this information should be taken into account in formulating their placement problem. Furthermore, despite the advances in related technologies, it is almost impossible to guarantee occasional device or communication failure that will lead to loss of data to be received from a given PMU. This paper illustrates how the measurement design can be made reliable against such events while maintaining the cost of PMU installations at a minimum by using strategically placed PMUs with the proper number of channels. Numerical results are given for small to large size power systems to illustrate the typical numbers of PMUs and their channel capacities that are required for optimal performance.

Detection, identification, and correction of bad sensor measurements for fault location

We initially review the readily devised methodology for transmission-grid disturbance location employing measurements from strategically deployed sensors. Later, we introduce one viable procedure for bad measurement detection and identification in order to accurately localize power system faults, thereby to enhance the practicality of the developed method. Furthermore, subsequent elimination of the errors resulting from bad sensor measurements will yield significantly enhanced fault-location accuracy. Simulated data regarding a particular fault scenario are illustrated using the modified IEEE 30-bus test grid.

An attack-resilient fault-location algorithm for transmission grids based on LAV estimation

We priorly review the existing methodology for transmission-grid fault location utilizing synchronized measurements that are retrieved from optimally placed sensors. Then, we develop an enhanced protection strategy for guarding against cyberattacks, thus achieving a robust fault location in transmission systems. As such, autocorrection of corrupted sensor measurements using the equality-constrained least-absolute-value (LAV) state estimator will secure the transmission grid against vulnerabilities caused by cyberattacks on synchronized measurements. The proposed algorithm is tested using a particular fault scenario on the IEEE 57-bus transmission grid.

Optimal sensor deployment for fault-tolerant smart grids

This study aims to present an optimal sensor deployment procedure that ensures robust and unique localization of line faults appearing in smart grids. In analogy to synchronized sensor networks in wireless communications, we initially model the grid as a wired mesh network, in which nodes are connected through power lines. Based on the topology of the network and distance measurements among electrical nodes, a fault-localization technique is then established. The method relies on recorded time-of-arrival (ToA) measurements at nodes which are equipped with synchronized sensors. Identification of the location for any fault is achieved via sensors which are deployed in a minimal fashion. Measurement errors on synchronized sensors are also handled with the successful application of a bad data processing technique. The performance of the overall algorithm is realized through an implementation on a 57-node power grid.