Failure analysis and dispatch optimization using phasor measurement units
Introduction
In new smart grids, the new technologies are fully interconnected and they allow the analysis and stress the system for a better utilization of the assets. To ensure the safety of the operation of the PS, an arduous analysis is required in terms of the large number of variables and possible operating stages, it could occur due to topological changes in the power system, demand curves, dispatches, or renewable generation resources; it represents a constant challenge for network analysts and failure analysis engineering [1].
One of the technological developments aimed at improving the safety of electricity networks is the Phasor Measurement Units (PMU), because of it, the PMU allow a better estimation of operating variables (synchronization, angle, event registration, among others.) and almost complete observability of the power system [2].
Several PMU's applications consist of strengthening the analysis of electrical networks by evaluating the angular differences that exist between lines or areas that are considered weak and / or critical. Basically, is given in a stress stage, these can show great angular differences between these areas and if these angular differences are very high they increase the risk of generating a high impact event or in the worst case the collapse of the electrical system [3].
According to the above, theories that combine phasor measurements with the circuital laws of a PS have been developed, in order to determinate the stress level of specific areas. One of the challenges to carry out these analyzes consists of dividing an electrical network into electrical areas or cutting areas in such a way that the concept of cutting angle can be applied making use of the PMUs and thus obtaining sensitivities determined by the level of stress of one area with respect to others [4].
The function of an electric power system is to convert energy from one of the naturally available forms to the electrical form and transport it to the points of consumption. The advantage of the electrical form of energy is the following aspects: Control and transport improvement, with relative ease and with a high degree of efficiency and reliability.
A properly designed and operated power system should therefore, meet the following fundamental requirements:
- (a)
The system must be able to meet the continually changing load demand for active and reactive power. Unlike other types of energy, electricity cannot be conveniently stores in sufficient quantities. Therefore, adequate “spinning” reserve of active and reactive power should be maintained and controlled at all times.
- (b)
The system should supply energy at minimum cost and with minimum ecological impact.
- (c)
The “quality” of power supply must meet certain minimum standards with regard to the following factors:
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“Constancy of frequency” [23].
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“Constancy of voltage” [22].
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“Reliability level” [10].
For reliable service, a bulk electricity must remain intact and be capable of withstanding a wide variety of disturbance, and so that the most adverse possible contingencies do not result in uncontrolled, widespread and cascading power interruptions.
The extreme contingency assessment recognizes that interconnected bulk PS could be subjected to events that exceed in severity the normal design contingencies. The objective is to determine the effects of extreme contingencies on system performance in order to obtain an indication of system strength and to determine the extent of a widespread system disturbance even though extreme contingencies do have very low probabilities of occurrence. After an analysis and assessment of extreme contingencies, measures are to be utilized, where appropriate, to reduce the frequency of occurrence of such contingencies or to mitigate the consequences that are indicated, as a result of such contingencies [4].
PS is designed to withstand normal events; therefore, modern protective relays are designed to handle these normal events. On the other hand, other power system events like transmission line outages will require wide area remedial actions to preserve power system stability and to avoid damage to other equipment that might get overloaded. In general, such events will result in significant topological changes and affect the power system stability. Remedial actions such as load shedding are often required to bring the system back to a new stable state.
In this research, a new methodology is developed to divide a PS into electrical or cutting areas using the k-means algorithm, in such a way that when applying angular theories. It allows to determine the interaction of one area with respect to another when contingencies occur in different points of the system and preventive actions can be taken to avoid cascading events.
Section snippets
Theory and analysis
This paper has considered the algorithm in SCOPUS and ScienceDirect, as follows: (PMU)AND(Power)AND(Cluster)AND(k-means). We have analyzed 42 research articles; the main challenges in the new projects associated to PMU are described in the following:
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The “false data injection requires algorithms for clustering process, in order to detect false signals” [29], especially for wind farms, due to “fixed termination time for stepwise inertial control” of wind turbine generators [23], [30]. Due to
New methodology proposed
To perform analysis of angular sensitivities to presented contingencies, applying the concept of cutting angle, it is necessary to divide an electrical PS into areas in such a way that the cuts are clearly defined, however the division through cuts couldńt be arbitrary, which requires establishing a methodology for defining them.
Case study implementantion with a new methodology
The network considered for the application of the methodology is the “New England” system of 39 nodes. The language used to implement the methodology is DPL language from DigSilent and Visual Basic.
(A) Case study I.
In this case, the analysis of a fixed cut for two different dispatches will be carried out, in this way a comparison of the sensitivity results can be made to determine how stressed one area is with respect to another.
Applying the proposed methodology, it is chosen to divide the
Discussion
We show the typical configuration of a substation with its Capacitive Voltage Transformer (CVT) and Current Transformers (CTS, CTM for a breaker and a half scheme if required, and CTR or CTB for shunt reactor) that are used as the inputs for the DACA [41]. The figures show connections with the PMCU’s equipment, in the Fig. 9.
During steady-state operating conditions, the voltage magnitudes of the network buses are close to one per unit. That is, the real power transfer capability mainly depends
Conclusions
From the results, it can be shown that the angular sensitivity factors are affected with the changes in dispatches and demands. While, the deviation factor can take large variations depending on the operational condition of demand and dispatch; therefore, if the analysis of the two factors is combined, then the behavior of the network seen from the cutting angle could be analyzed completely [20].
The pre-fault and post fault data recorded for the PMU matches the exact location for the
Author Contribution Statement
Ricardo Manuel Arias Velásquez: Conceived and designed the experiments and models, analyzed and interpreted the data, wrote the paper with materials and modelling.
Declaration of competing interest
There is no conflict of interest in this work.
Acknowledgments
Recognition to Universidad Nacional de San Agustín de Arequipa.
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