Analysis of PMU under transient processes

The electrical power system is becoming more and more complex with the increasing demand of the electricity across the world, as the world is becoming the global village. The electrical power system must be reliable and safe enough to fulfil the energy requirements with the continuous supply of energy. The chances of power system's blackouts and outages are increasing with its increased complexity. So, there is a need of an efficient control system to make the power system more safe, efficient and reliable. Wide Area Monitoring, Protection and Control system (WAMPAC) is becoming an emerging technology for an efficient monitoring, protection and control of power system. Phasor measurement unit (PMU) is an integrated part of wide area monitoring, protection and control (WAMPAC) system, which can be used for monitoring, protection and control of complex electrical power systems. PMU gives the synchronized phasor measurements of voltage and current and can easily monitor and control even small disturbances in power system to protect the power system from any blackouts and outages before any fault occurs. In the proposed paper a PMU model is designed in MATLAB/Simulink and then PMU is used for power system protection and the comparative analysis are done with the conventional protection technique for an interconnected two-area network power system.

There have been quite a few attempts to compute synchronous generator parameters based on voltage and current synchrophasors taken under power system transients. However, we have not seen any publications with thorough analysis as to how soon the phasor measurement unit reacts to disturbance conditions, which components of the transient are filtered out and which are passed through, as well as what the total vector error is. The goal of this research is to determine all of these characteristics of a phasor measurement unit when playing back transient oscillograms for a stator short circuit obtained through mathematical modeling. The transient oscillograms have been derived via both a full Park-Gorev system of flux linkage equations as well as the MATLAB/Simulink Synchronous Machine block. Physical modeling was then conducted via a real-time digital simulator (RTDS) along with a dedicated phasor measurement unit ENIP-2 (PMU), and the stator current phasors were recorded. Our analysis has shown that both RTDS and ENIP-2 (PMU) almost entirely filter out the exponentially decaying DC component of the fault current while closely following the periodical signal envelope. The total vector error has been estimated to become below 1–2 % after around 0,02–0,03 s into the fault when selecting the “P” class filters according to IEEE C37.118. We have come to a conclusion that synchrophasor measurements under power system disturbances could be utilized for estimating the synchronous, transient, and subtransient generator parameters. The selected synchronous machine model in the form of flux linkage equations is correct, as the obtained transient oscillograms are exactly the same as those produced by Simulink. “P” class phasor measurements can be recommended for representing transients in the stator circuit of a synchronous generator. The results of this investigation are meant to be employed for synchronous machine parameter estimation based on phasors sourced from RTDS and, hopefully, from phasor measurement units installed at power plants.

In Japan, to realize low-carbon society, Advanced Low Carbon Technology Research and Development (ALCA) Project has been promoted to develop low-carbon technologies. The hydrogen cooled super-conducting generator (SCG) is one of them. SCGs have advantages such as low synchronous reactance and expansion of leading power factor operation, which expands the stability limit of power grid. Therefore, hydrogen cooled SCGs can be effective not only to low carbonization but also to stabilize high renewable energy (RE) penetration power grid. This study intend to model SCG with quick response excitation on electromagnetic transient (EMT) analysis software named eXpandable Transient Analysis Program (XTAP) and analyze grid stability, behavior of machines at power system fault situation, etc. accurately in order to reveal advantages of installing SCGs with quick response excitation.

As Electrical power system is moving very rapidly toward greener and more sustainable through the usage of Distributed Energy Resources (DERs), complexity and dynamic nature of power system is increasing at a same pace also, Thus to avoid any instability or faults that might occur, quick and real time monitoring of electrical power system is the need of the day. This can be achieved by the usage of Phasor Measurement Units (PMUs). PMU is a time-synchronized metering device that gives very fast and precise data of current and voltage phasors. However, due to their high infrastructure costs of placing, adequate planning for PMU placement is crucial so that the whole system can be observable and the cost of installation of PMUs can be reduced also. In this paper we present optimal PMU placement through Binary Integer Linear Programming (BILP). The simulations are carried out for normal conditions as well as N-1 contingencies. Furthermore, to solve Multiphase PMUs placement problem Multi Criteria Decision Making (MCDM) has been employed. The presented technique is applied on Pakistani Transmission Network as well as on IEEE 14 bus system. The results show that with less number of PMUs better observability of critical buses and lines can be achieved in Pakistani Transmission system as well as in IEEE test systems.

Electromagnetic transients are the tidal waves of electric power systems. These momentary voltage surges generally lasting only fractions of a second can be powerful enough to disrupt normal operations and even cause serious damage to major pieces of equipment, such as transformers. Created by lightning, line faults, substation switching functions, and other sudden events along a utility network, transients must be taken into account both in choosing equipment ratings for a power system and in setting its operating parameters. Like the builders of a seawall that must withstand the highest expected waves from the ocean, engineers trying to guard against damage from transients face an extraordinary design task. Most of the huge computer simulation codes related to power systems either model steady-state conditions or deal with system stability problems. The analysis of electromagnetic transients, on the other hand, requires a much more detailed examination of how some critical portion of a power system will react to conditions that can change greatly in microseconds. For many years, simulation of transient effects was performed by special-purpose analog computers called transient network analyzers (TNAs). These machines, which are still in use, recreate a portion of the power system in miniature, complete with voltage sources representing generators and various kinds of capacitive or inductive loads. TNAs are generally adequate but relatively inflexible, tedious to set up, and cumbersome to use. Once a system configuration is modeled, many simulations can be performed. Given the need to manually reconfigure TNA circuits to represent changes in a system, however, the analyzers can also be quite expensive to use. During the late 1960s, Herman Dommel of the Bonneville

The lightning overvoltage is one of important parameter in designing the insulation of transmission line and power apparatus. Usually the influence of the impulse corona is ignored in numerical analysis of electromagnetic transients in power systems. This paper presents a corona model on an HV transmission line under the influence of lightning strike and impulse voltage. This model shows two main developments in the modeling of power transmission line for the simulation of electric network. The first one is a wide bandwidth circuit corona model and the second a phase-domain multiphase full frequency-dependent line model. Both models have been developed in the Electromagnetic Transients Program (EMTP-RV). At the end of this paper, effects of skin effect and radius conductor on lightning overvoltage are considered.

Nowadays, there is quite high demand for electromagnetic transient (EMT) analysis programs and real-time simulators for power systems. In addition to the conventional demand such as overvoltage, over-current and oscillation simulations, the new demand that includes simulations of power-electronics circuits and power quality is increasing. With this background, development groups of EMT programs and real-time simulators have made progress in terms of computational performance and user experience. In Japan, Central Research Institute of Electric Power Industry has newly developed an EMT analysis program called XTAP (eXpandable Transient Analysis Program). This article overviews these international and domestic development trends of EMT analysis programs and real-time simulators.

Application of heuristic algorithms to optimal PMU placement in electric power systems: An updated review

Several tools have been used over the years to analyze electromagnetic transients in power systems. The digital computer is the most popular tool, although TNAs and the new generation of real-time digital systems are also used, mainly in applications for which either a very high-speed or a real-time simulation is required. Many techniques have been developed to solve electromagnetic transients using a digital computer. They can be classified into two main groups: frequency-domain and time-domain techniques. The subject of this paper is the digital simulation of electromagnetic transients in power systems using a time-domain technique.

The wavelet transform is introduced as a method for analyzing electromagnetic transients associated with power system faults and switching. This method, like the Fourier transform, provides information related to the frequency composition of a waveform, but it is more appropriate than the familiar Fourier methods for the nonperiodic, wide-band signals associated with electromagnetic transients. It appears that the frequency domain data produced by the wavelet transform may be useful for analyzing the sources of transients through manual or automated feature detection schemes. The basic principles of wavelet analysis are set forth, and examples showing the application of the wavelet transform to actual power system transients are presented.

Distributed generation (DG) has changed the energy landscape by increasing system reliability and decreasing environmental impacts through its incorporation into electrical power systems. The additional complexity brought forth by DG, however, also calls for the creation of more precise and effective fault finding techniques. This abstract explores current developments in fault localization strategies for DG-integrated electrical power systems using deep learning (DL) methods. Due to the non-linear, dynamic, and ever-changing nature of DG-rich networks, traditional fault finding algorithms generally struggle to correctly locate faults in these networks. Deep learning's potential as a solution may be seen in its capacity to recognise complex patterns and adjust to new information. Specifically, this study looks into how DL models like CNNs and RNNs can be used to improve the precision with which faults can be detected and localised in DG-integrated power systems. The creation of DL-based fault location algorithms that use high-resolution data from different sensors like smart metres and phasor measurement units (PMUs) is a major advancement. These algorithms draw on the temporal and spatial information available in power system data to pinpoint the exact location of malfunctions. Additionally, the study looks into the stability and transferability of DL models using various DG technologies and setups. Pre-trained models are transferred learning approaches to guarantee adaptability and reliability across a wide range of DG applications. The findings show that in DG-rich contexts, fault location algorithms based on DL perform much better than their conventional counterparts. These developments have the potential to strengthen electrical grids, reduce the frequency and duration of outages, and improve the reliability of today's power systems. The incorporation of deep learning into fault location algorithms is an important step towards building a more dependable and robust power system, especially as DG integration continues to grow

The concept of Wide-Area Measurement Systems (WAMS) envisages the transmission of current and voltage phasor samples from remote Phasor Measurement Units (PMUs) to control centres, relays or controllers. Compression of the high frequency samples of sinusoidal waveforms into phasors is usually done using Discrete-Fourier Transform(DFT)-like algorithms. The phasor data is normally useful only when the system is in sinusoidal steady state, or nearly so. It is worthwhile to explore means to get reasonably accurate transient information as well, even if it means that some additional compressed information needs to be transmitted from the PMUs. Transient reconstruction has practical utility in the analysis of disturbances (at a remote control centre) and for flagging the initiation and clearing of network disturbances, which may be required for some WAMS analytics. In this paper, it is shown that one-cycle-delayed reconstruction of power system transient waveforms can be done with samples of the dc, fundamental and harmonic phasors reported at a rate of one sample per cycle obtained from the DFT algorithm. For power system transients, a few harmonics are usually adequate to reconstruct the transient waveforms with reasonable accuracy. The paper explains the reconstruction method, presents illustrative examples and discusses possible applications and practical issues.

Nowadays, the increase in electrical energy consumption and power system restructuring have posed new challenges to the operation, control, and monitoring of power systems. In this situation, the supervisory control and data acquisition (SCADA) system is not enough to ensure power system security and stability. The SCADA is often unable to measure data of all buses simultaneously. In addition, the sampling rate in this system is not enough for some power system applications. Therefore, the information obtained from SCADA does not show power system dynamics properly. In order to improve the power system monitoring, wide area measurement system (WAMS) has been developed to overcome the problems of SCADA system. Phasor measurements units (PMUs) are the main part of WAMS system and it basically consists of three essential processes including collecting, transmitting, and analyzing data. WAMS receives obtained data via a high speed communication links. After data processing and extracting appropriate information, decisions are made to improve the power system performance. Efficient use of power system data to achieve a secure operation strategy is targeted using the WAMS system. Due to the effective role of WAMS and PMUs in the reliable operation of power system, it is necessary to study their concept and applications in this chapter. The history of PMU and its structure is presented in this chapter. In addition, the necessity of WAMS for future power system and its difference from SCADA system have been investigated in this chapter. Different algorithms and application of the WAMS are also introduced in this chapter which can be implemented to improve the performance of the future power system.

An electric power system sometimes fails because of disturbances that occur unexpectedly, such as the uncontrolled loss of load that developed from cascading blackout. Which make stability through a little of under voltage load shedding should work. The development of phasor measurement unit(PMU) makes network supervision possible. The information obtained from PMU is synchronized by global positioning system(GPS). There are many real-time algorithms which are monitoring the voltage stability. This paper presents the study on the VILS(Voltage Instability Load Shedding) using PMU data. This algorithm computes Voltage Stability Margin Index(VSMI) continuously to track the voltage stability margin at local bus level. The VSMI is expressed as active and reactive power. The VSMI is used as an criterion for load shedding. In order to examine the algorithm is effective, applied to KEPCO system.

Synchrohasor measurement is a common tool to monitor system stability and detect faults in electric power systems and various Phasor Measurement Units (PMUs) have been developed for this purpose. Parameter computation methods of PMUs specifically designed for rapidly time-varying voltage cases caused by nonlinear dynamic loads have been an attractive research topic. In this paper, instantaneous amplitudes and phases of the voltage signals are estimated using a method based on quadrature amplitude modulation complying with M class accuracy criteria defined by the IEEE Standard C37.118. It has been shown on simulated voltage data that the proposed method provides synchrophasor results satisfying the accuracy limits defined in IEEE Standard C37.118. The results of the proposed method have also been compared with those of the DFT method and the proposed method has been shown to be more advantages in terms of satisfying the accuracy limits and reducing processing time.