An efficient method to include equality constraints in branch current distribution system state estimation

Distribution system state estimation is a fundamental tool for the management and control functions envisaged for future distribution grids. The design of accurate and efficient algorithms is essential to provide estimates compliant with the needed accuracy requirements and to allow the real-time operation of the different applications. To achieve such requirements, peculiarities of the distribution systems have to be duly taken into account. Branch current-based estimators are an efficient solution for performing state estimation in radial or weakly meshed networks. In this paper, a simple technique, which exploits the particular formulation of the branch current estimators, is proposed to deal with zero injection and mesh constraints. Tests performed on an unbalanced IEEE 123-bus network show the capability of the proposed method to further improve efficiency performance of branch current estimators

Missed care: indagine esplorativa nelle medicine dell'ulss 15

Problema. Le cure perse sono rappresentate da qualsiasi cura infermieristica necessaria al paziente che viene però omessa o rimandata. Sono presenti all'interno delle realtà sanitarie internazionali e rappresentano un indicatore della qualità delle cure offerte. Tale fenomeno è interpretato tramite il Missed Nursing Care Model, secondo cui contribuiscono al verificarsi di questa problematica gli antecedenti (risorse umane, materiali e comunicazione non adeguati), gli elementi del processo di nursing, le percezioni degli infermieri e il processo di decisione (valori, credenze, abitudini). Le cure perse portano allo sviluppo di conseguenze negative sui pazienti (es. allungamento degenza, disabilità, lesioni) e sugli operatori sanitari (es. insoddisfazione lavorativa, abbandono del lavoro, rabbia). Compito dell'infermiere è per questo cercare di limitarle il più possibile per garantire maggiore sicurezza ai pazienti. Obiettivo. Lo studio indaga tale fenomeno nelle medicine dell'Azienda Ulss 15 (Alta Padovana) per identificare quali siano le cure perse più frequenti e capire quali siano, secondo gli infermieri, le cause più rilevanti. Materiali e Metodi. L'indagine è stata condotta tramite la somministrazione di un questionario che riprende uno strumento validato, il Missed Nursing Care Survey, proposto agli infermieri delle Unità Operative di Medicina 1 e 2 del Presidio Ospedaliero di Cittadella e di Geriatria e Medicina generale del Presidio Ospedaliero di Camposampiero. Risultati. Dai risultati è emerso che le cure perse ritenute più frequenti sono la deambulazione del paziente tre volte al giorno o come da pianificazione (90%) e la mobilizzazione passiva ogni due ore (76%). Mentre le cause ritenute più rilevanti sono l'inadeguato numero di personale sanitario (92%) e l'elevato numero di ricoveri/dimissioni durante il turno (92%). Tali risultati sono sovrapponibili a quelli di uno studio simile effettuato su alcuni ospedali del nord est italiano. Conclusioni. Le cure perse sono una problematica effettiva e non ci sono ancora soluzioni comprovate, ma si possono attuare forme di presa di coscienza del fenomeno e di compensazione in attesa della creazione di standard nazionali e provvedimenti istituzionali per la risoluzione delle cause.ope

PMU-based distribution system state estimation with adaptive accuracy exploiting local decision metrics and IoT paradigm

A novel adaptive distribution system state estimation (DSSE) solution is presented and discussed, which relies on distributed decision points and exploits the Cloud-based Internet of Things (IoT) paradigm. Up to now, DSSE procedures have been using fixed settings regardless of the actual values of measurement accuracy, which is instead affected by the actual operating conditions of the network. The proposed DSSE is innovative with respect to previous literature, because it is adaptive in the use of updated accuracies for the measurement devices. The information used in the estimation process along with the rate of the execution are updated, depending on the indications of appropriate local metrics aimed at detecting possible variations in the operating conditions of the distribution network. Specifically, the variations and the trend of variation of the rms voltage values obtained by phasor measurement units (PMUs) are used to trigger changes in the DSSE. In case dynamics are detected, the measurement data are sent to the DSSE at higher rates and the estimation process runs consequently, updating the accuracy values to be considered in the estimation. The proposed system relies on a Cloud-based IoT platform, which has been designed to incorporate heterogeneous measurement devices, such as PMUs and smart meters. The results obtained on a 13-bus system demonstrate the validity of the proposed methodology that is efficient both in the estimation process and in the use of the communication resources

Refined Modeling and Compensation of Current Transformers Behavior for Line Parameters Estimation Based on Synchronized Measurements

Nowadays, in modern management and control applications, line parameters need to be known more accurately than in the past to achieve a reliable operation of the distribution grids. Phasor measurement units (PMUs) may improve line parameter estimation processes, but the accuracy of the result is affected by all the elements of the PMU-based measurement chain, in particular by the instrument transformers. Current transformers (CTs) are nonlinear and, therefore, their behavior is not easily described: their models cannot be straightforwardly included in the estimation problem. In this regard, this article refines modeling and compensation of CT systematic errors in line parameter estimation processes, based on different methods to describe the transformer behavior under various operating conditions. As the main result, the systematic errors of CTs are remarkably identified and mitigated. Moreover, the estimation of shunt susceptance values is significantly improved

Bayesian Approach for Distribution System State Estimation With Non-Gaussian Uncertainty Models

To deal with the increasing complexity of distribution networks that are experiencing important changes, due to the widespread installation of distributed generation and the expected penetration of new energy resources, modern control applications must rely on an accurate picture of the grid status, given by the distribution system state estimation (DSSE). The DSSE is required to integrate all the available information on loads and generators power exchanges (pseudomeasurements) with the real-time measurements available from the field. In most cases, the statistical behavior of the measured and pseudomeasured quantities cannot be approximated by a Gaussian distribution. For this reason, it is necessary to design estimators that are able to use measurements and forecast data on power flows that can show a non-Gaussian behavior. In this paper, a DSSE algorithm based on Bayes's rule, conceived to perfectly match the uncertainty description of the available input information, is presented. The method is able to correctly handle the measurement uncertainty of conventional and synchronized measurements and to include possible correlation existing between the pseudomeasurements. Its applicability to medium voltage distribution networks and its advantages, in terms of accuracy of both estimated quantities and uncertainty intervals, are demonstrated

PMU’s behavior with flicker-generating voltage fluctuations: an experimental analysis

Phasor measurement units (PMUs), which are the key components of a synchrophasor-based wide area monitoring system (WAMS), were historically conceived for transmission networks. The current trend to extend the benefits of the synchrophasor technology to distribution networks requires the PMU to also provide trustworthy information in the presence of signals that can occur in a typical distribution grid, including the presence of severe power quality (PQ) issues. In this framework, this paper experimentally investigates the performance of PMUs in the presence of one of the most important PQ phenomena, namely the presence of voltage fluctuations that generate the disturbance commonly known as flicker. The experimental tests are based on an ad-hoc high-accuracy measurement setup, where the devices under test are considered as “black boxes” to be characterized in the presence of the relevant signals. Two simple indices are introduced for the comparison among the different tested PMUs. The results of the investigation highlight possible critical situations in the interpretation of the measured values and provide a support for both the design of a new generation of PMUs and the possible development of an updated synchrophasor standard targeted to distribution systems

Genetic modifiers of Duchenne muscular dystrophy and dilated cardiomyopathy

OBJECTIVE: Dilated cardiomyopathy (DCM) is a major complication and leading cause of death in Duchenne muscular dystrophy (DMD). DCM onset is variable, suggesting modifier effects of genetic or environmental factors. We aimed to determine if polymorphisms previously associated with age at loss of independent ambulation (LoA) in DMD (rs28357094 in the SPP1 promoter, rs10880 and the VTTT/IAAM haplotype in LTBP4) also modify DCM onset. METHODS: A multicentric cohort of 178 DMD patients was genotyped by TaqMan assays. We performed a time-to-event analysis of DCM onset, with age as time variable, and finding of left ventricular ejection fraction 70 mL/m2 as event (confirmed by a previous normal exam < 12 months prior); DCM-free patients were censored at the age of last echocardiographic follow-up. RESULTS: Patients were followed up to an average age of 15.9 \ub1 6.7 years. Seventy-one/178 patients developed DCM, and median age at onset was 20.0 years. Glucocorticoid corticosteroid treatment (n = 88 untreated; n = 75 treated; n = 15 unknown) did not have a significant independent effect on DCM onset. Cardiological medications were not administered before DCM onset in this population. We observed trends towards a protective effect of the dominant G allele at SPP1 rs28357094 and recessive T allele at LTBP4 rs10880, which was statistically significant in steroid-treated patients for LTBP4 rs10880 (< 50% T/T patients developing DCM during follow-up [n = 13]; median DCM onset 17.6 years for C/C-C/T, log-rank p = 0.027). CONCLUSIONS: We report a putative protective effect of DMD genetic modifiers on the development of cardiac complications, that might aid in risk stratification if confirmed in independent cohorts

Isomorphism between Systems of Equivariant Singularities

AbstractIn this article isomorphisms between systems of singularities equivariant under different Lie group actions are investigated and a sufficient condition for two systems to be isomorphic is given. With this sufficiency theorem we show that the system ofO(n)-equivariant singularities in its irreducible representation on Rnis isomorphic to that of one-dimensional Z2-equivariant singularities and the system of[formula]-dimensionalO(n)-equivariant singularities is isomorphic to that ofn-dimensionalSn-equivariant singularities