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Stability Assessment and Control: Problem Descriptions and Classifications
Published in Yan Xu, Yuchen Zhang, Zhao Yang Dong, Rui Zhang, Intelligent Systems for Stability Assessment and Control of Smart Power Grids, 2020
Yan Xu, Yuchen Zhang, Zhao Yang Dong, Rui Zhang
The recent widespread use of the global positioning system (GPS) has made time synchronization and phase-angle measurements available. PMU is an electronic device that takes measurement of voltage/current phasors on a power grid, using a common time reference from the GPS. The hardware block diagram of a PMU is shown in Fig. 2.1 (A.G. Phadke and J.S. Thorp, 2008). Basically, the PMU converts the analogue voltage/current waveforms measured by potential/current transformers into digital measurement data. Adhering to the GPS time reference with an accuracy of 1 microsecond, the phasor-locked oscillator ensures that all the phasor measurements over the power grid are time-synchronized, meaning the whole grid is measured in a system-wide manner. Moreover, the measurement output rate of a PMU can reach up to 60 samples per second. With such high temporal resolution, PMUs are devices that facilitate taking real-time measurements.
An Overview of Smart Grid in Protection Perspective
Published in Ramesh Bansal, Power System Protection in Smart Grid Environment, 2019
A phasor measurement unit (PMU) is utilized in the smart grid to measure the electrical waves in the grid by means of a time source for synchronization. It is an important component in collecting real-time monitoring information for observability and controllability of smart grid operations. Owing to the importance of the smart grid, the synchrophasor has been produced in large quantities to improve the observability of the power system. A PMU is designed so that it allows synchronized real-time measurements of numerous remote points in the grid [39]. A PMU network is composed of PMUs at substations and generation stations, phasor data concentration (PDC) for collection of information, local communication networks and SCADA at control centres. The network is globally utilized in wide area measurement systems (WAMSs). The consequence of PMU network failure is so serious that it can cause a severe power outage. The PMU applications have been projected to enhance the reliability of the grid. Therefore, the reliability of a PMU network can be quantified using reliability indices [39]. A PMU is thought to be a standout amongst the most essential measuring devices that can be integrated into a protective relay or protection system.
State Estimation
Published in Antonio Gómez-Expósito, Antonio J. Conejo, Claudio A. Cañizares, Electric Energy Systems, 2018
Antonio Gómez-Expósito, Ali Abur
The measuring devices that can compute synchronized voltage and current phasors from time-stamped samples were initially developed by Phadke et al. [41,42]. The first implementation of GPS-synchronized phase-angle measurements in an industrial power system SE was presented in [43]. A PMU is a digital device providing synchronized voltage and current phasor measurements, referred to as synchrophasors [44]. Initial PMUs were designed as stand-alone units whose primary and only function was computation of synchrophasors. Gradually various types of intelligent electronic devices (IEDs) such as digital relays were retrofitted to function as PMUs in addition to their primary functions. Primary three-phase voltages and currents are converted to appropriate analog inputs by instrument transformers and anti-aliasing filtering. Each analog signal is digitized by an A/D converter with a sampling rate typically between 12 to 128 samples per cycle of the nominal power frequency. The sampling clock is phase-locked with the GPS clock pulse which provides the Universal Time Coordinated (UTC) time reference used to time-tag the outputs. Each PMU may have multiple input terminals that are used to connect three-phase voltage signal at the substation bus and three-phase current signals on one or more incident lines at the substation.
A comparative Studies on different islanding detection methods for distributed generation systems
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2023
Ashutosh Mohanty, Bidyadhar Rout, Raseswari Pradhan
PMU is a device that measures the PA and magnitude of electrical quantities like voltage, current, etc. (Kumar and Sarathee Bhowmik 2017). The measuring unit is generally located at substations that use a time used in the global positioning system, which gives a synchronized view of the grid performance (Radhakrishnan, Sankar, and Rajan 2020). PMU can collect the data sample quickly using phasor data concentrators and reconstruct the signal using the measured magnitude and PA. In the PMU, the measurement of both interconnected regions and islanded regions is utilized for islanding detection purposes (Barczentewicz et al. 2021). This approach is very effective for predetermined line outages. The NDZ is eliminated and no PQD is observed. The circuit is more costly to implement (Barkakati, Sen Biswas, and Pal 2019).
A New Backup Protection Scheme for Transmission Lines with Limited Phasor Measurement Units
Published in Electric Power Components and Systems, 2022
Mohammadreza Ahmadinia, Javad Sadeh
In this paper, a new backup protection scheme for transmission lines has been proposed by exploiting a limited number of PMUs. The PMUs have been located optimally in a way that at least one PMU is installed on either side of each transmission line. By this means, every fault in the network is observable and the power system can be divided into a number of predefined zone_types. In the recommended technique, the faulted area is firstly detected and then, the faulted zone and faulted line are determined. Contrary to the existing methods, the proposed scheme does not require the pre-fault data. In addition, it provides a precise backup protection for shunt-compensated transmission lines as well as the uncompensated ones. The high-resistance fault to ground have been also found accurately by the provided algorithm through the negative-sequence currents. The simulation results for various fault types in the uncompensated and the shunt-compensated lines illustrate the high effectiveness of the proposed methodology. Furthermore, the presented scheme does not activate securely in non-fault conditions such as load encroachment and power swing.
SCADA and PMU Measurement Based Methods for Robust Hybrid State Estimation
Published in Electric Power Components and Systems, 2019
Anamika Dubey, Saikat Chakrabarti, Vladimir Terzija
The advent of phasor measurement units (PMUs) made it possible to get the measurements at every few milliseconds [3]. A SE based on PMU measurements can update the states of the system at sub-second rate. A PMU provides synchronized bus voltage phasors, line current phasors, system frequency, and the rate of change of system frequency. These measurements are comparatively much more accurate than the conventional SCADA measurements. In the PMUs, measurement reporting rate is usually up to 50 (for 50 Hz system) or 60 (for 60 Hz system) times per second, that is much higher than the reporting rate of conventional SCADA measurements (typically few seconds) [4].