A flexible approach for overcurrent relay characteristics simulation

Accurate models of overcurrent (OC) with inverse time relay characteristics play an important role for the coordination of power system protection schemes. This paper proposes a new method for modelling OC relays curves. The model is based on fuzzy logic and artificial neural network. The feedforward multilayer perceptron neural network is used to calculate the operating times of OC relays for various time dial settings (TDS) or time multiplier settings (TMS). The new model is more accurate than traditional models. The model has been validated by comparing the results obtained from the new method with linear and nonlinear analytical models

Improving the performances of the autoregressive method in modal identification of output-only systems using Hilbert vibration decomposition method

In this paper, an enhanced method for extraction of modal parameters (frequencies and damping ratios) of a structure from stationary or non-stationary measurement dynamic responses recorded by a sensor is presented. Surely, one of the simplest methods in area of ambient modal identification (operational modal analysis) is autoregressive method. Major problem of autoregressive method is that for identification of m modes of a structure, at least m sensors are needed. Besides, this method like other similar methods in this area such as frequency domain decomposition and stochastic subspace identification is appropriate for extraction of modal parameters from stationary measured dynamic structural responses. To address these issues, in this study, the Hilbert vibration decomposition method, which is a simple method for time-varying vibration decomposition based on the Hilbert transform, is adopted to improve the performance of the autoregressive method for extraction of frequencies and damping ratios of a structure from stationary or non-stationary responses recorded by a sensor. The efficiency and performance of the newly enhanced method are investigated through two numerical examples and a verification example. The first numerical example deals with a single-degree-of-freedom system subjected to a non-stationary force and the second one presents a two-degree-of-freedom structure excited by a stationary force. Finally, by using the proposed method, the frequencies and damping ratios of a support tower of the segmental bridge via an experimental test are obtained. The results indicated that the proposed method adequately estimated the frequencies and damping ratios of a structure from stationary and non-stationary responses recorded by only one sensor. Moreover, it is found that this method outperforms other relevant methods when dealing with non-stationary responses. Consequently, the enhanced method is strongly recommended for extraction of the frequencies and damping ratios of the structures from stationary or non-stationary responses, especially when the dynamic response of the structure is non-stationary and measured using only one sensor

A new optimal approach for coordination of overcurrent relays in interconnected power systems

In this paper, a new method for optimum coordination of overcurrent relays is proposed. The proposed method is based on only constraints. Minimization is inherently included by setting the time dials to minimum and increasing their values gradually. Configuration changes of the network are taken into account. The method does not need any initial solution. It can consider both linear and nonlinear relay characteristics models. The optimal settings of overcurrent relays for 8-Bus and England Norweb networks are obtained and comparison between the new method and existing methods is made

Exploring User-Suitable Metaphors for Differentially Private Data Analyses

Despite recent enhancements in the deployment of differential privacy (DP), little has been done to address the human aspects of DP-enabled systems. Comprehending the complex concept of DP and the privacy protection it provides could be challenging for lay users who should make informed decisions when sharing their data. Using metaphors could be suitable to convey key protection functionalities of DP to them. Based on a three-phase framework, we extracted and generated metaphors for differentially private data analysis models (local and central). We analytically evaluated the metaphors based on experts\u27 feedback and then empirically evaluated them in online interviews with 30 participants. Our results showed that the metaphorical explanations can successfully convey that perturbation protects privacy and that there is a privacy-accuracy trade-off. Nonetheless, conveying information at a high level leads to incorrect expectations that negatively affect users\u27 understanding and limits the ability to apply the concept to different contexts. In this paper, we presented the plausible suitability of metaphors and discussed the challenges of using them to facilitate informed decisions on sharing data with DP-enabled systems

A Three-Dimensional Surface Velocity Field for the Mississippi Delta: Implications for Coastal Restoration and Flood Potential

Accurate estimates of the current rate of subsidence in the Mississippi Delta (southern United States) provide a context for planning of wetland restoration and predictions of storm surge flooding. We present a comprehensive three-dimensional surface velocity field for the Mississippi Delta based on a network of 36 high-precision continuous GPS stations. We show that while the majority of the delta is relatively stable, the southern portion continues to experience high rates of subsidence (5–6 mm yr–1). Our data are consistent with long-term tide gauge records at Grand Isle, Louisiana, and several stations in Florida. The current rate of relative sea-level rise (combined effect of land subsidence and sea-level rise) along parts of the coastal delta is ∼8–9 mm yr–1. Most tide gauge stations have recorded sea-level-rise acceleration after A.D. 1970. These data have implications for land reclamation and wetland restoration in the region; parts of the delta may not be viable in the long term

Subsidence along the Atlantic Coast of North America: Insights from GPS and late Holocene relative sea level data

The Atlantic Coast of North America is increasingly affected by flooding associated with tropical and extratropical storms, exacerbated by the combined effects of accelerated sea‐level rise and land subsidence. The region includes the collapsing forebulge of the Laurentide Ice Sheet. High‐quality records of late Holocene relative sea‐level (RSL) rise are now available, allowing separation of long‐term glacial isostatic adjustment‐induced displacement from modern vertical displacement measured by GPS. We compare geological records of late Holocene RSL to present‐day vertical rates from GPS. For many coastal areas there is no significant difference between these independent data. Exceptions occur in areas of recent excessive groundwater extraction, between Virginia (38°N) and South Carolina (32.5°N). The present‐day subsidence rates in these areas are approximately double the long‐term geologic rates, which has important implications for flood mitigation. Tide gauge records, therefore, should be used with caution for studying sea‐level rise in this region