(Pdf) vulnerability of zigbee to impulsive noise in electricity substations electricity towers health risks


In smart grid, standardized control networks are typical safety critical components which are under the environments with strong noise and interferences. This paper focuses on the safety mechanisms of standardized control networks in smart grid. The underlying safety mechanisms of standardized wired control networks are analyzed deeply. More importantly, there are very few works considering the safety extensions for wireless control networks. To address this, we propose a combined cyclic redundancy check (CRC) based safety extension mechanism. In addition, key points and open issues of safety-related mechanisms are discussed. To evaluate the safety of the proposed combined CRC mechanism for wireless control networks, error correction capability simulation is performed, which validates the effectiveness of the proposed scheme under the typical noisy background in smart grid. The result supports the usefulness and feasibility of our scheme. To the best of our knowledge, this work is the first to focus deeply on the safety mechanisms for standardized control network in smart grid, especially for the safety extension scheme for wireless control networks.

One physical electricity trading hedge funds process, which is not adequately described in terms of Gaussian models, is the process that generates “impulsive” interference bursts. These bursts occur in the form of short duration interferences, attaining large amplitudes. Many natural sources of interference exist, including lightning in the atmosphere or ice cracking in the arctic region. Among the manmade sources dominant source of impulsive interference occurs in the electricity supply industry. These noises can cause significant degradation of the performance of conventional wireless communication systems. This paper introduces a concept of impulsive noise reduction utilizing the Empirical Mode Decomposition (EMD) framework, where noisy signal is decomposed adaptively into oscillatory components called Intrinsic Mode Functions (IMFs) by means of a process called sifting. The EMD denoising involves filtering or thresholding each IMF and reconstructs the estimated signal using the processed IMFs. To simulate the denoising phenomenon, input information signals, impulsive noises and EMD algorithms were generated in Matlab. The input signals were degraded by adding impulsive noise and then empirical mode decomposition was performed on the noisy signals. Simulation results suggest that a signal corrupted by impulsive electricity towers health risks noise can be considerably recovered by the EMD method.

We introduce algorithms and conceptual circuits for Nonlinear Differential Limiters (NDLs), and outline a method- ology for their use to mitigate in-band noise and interference, especially that of technogenic (man-made) origin, affecting vari- ous real, complex, and/or vector signals of interest, and limiting the performance of the affected devices and services. At any given frequency, a linear filter affects both the noise and the signal of interest proportionally, and when a linear filter is used to suppress the interference outside of the passband of interest gas welder job description, the resulting signal quality is invariant to the type of the amplitude distribution of the interfering signal, as long as the total power and the spectral composition of the interference remain unchanged. Such a linear filter can be converted into an NDL by introducing an appropriately chosen feedback-based nonlinearity into the response of the filter, and the NDL may reduce the spectral density of particular types of interferences in the signal passband without significantly affecting the signal of interest. As a result, the signal quality can be improved in excess of that achievable by the respective linear filter. The behavior of an NDL filter and its degree of nonlinearity is controlled by a single parameter in a manner that enables significantly better overall suppression of the noise compared to the respective linear filter, especially when the noise contains components of technogenic origin. Adaptive configurations of NDLs are similarly controlled by a single parameter, and are suitable for improving quality of non-stationary signals under time-varying noise conditions. NDLs are designed to be fully compatible with existing linear devices and systems, and to be used as an enhancement, or as a low-cost alternative, to the state-of-art interference mitigation methods.

Installation of wireless sensor networks in power substations is becoming unavoidable for developing smart electrical network. High-voltage equipment in a power substation may produce impulsive noise that happens to be much more troublesome for wireless communications than gas prices in texas conventional white noise. Indeed, the choice of physical layer for communication network is not easy. It fits to evaluate attentively the advantages and downsides bound to the different technologies of communication. Before deploying the network, electromagnetic environment has to be characterized and tests have to be performed in order to estimate communication performances. This paper presents an investigation of ZigBee (IEEE 802.15.4/2.4 GHz) narrowband system performance in high voltage substations. We use recorded data from the measurement campaign to identify the models. Substation noise obtained is modeled as a Middleton Class A process and a recent model (Au). By using several statistical tests, we evaluated the two models. First, the results show that Middleton Class A is not accurate for modeling partial discharges at 735 kV electricity substations. Au model is more accurate to model impulsive noise in high voltage substation compare to Middleton Class A and Gaussian models. In addition, the BER performances of the ZigBee 2.4 GHz PHY layer are studied in a substation environment. The results show that the impulsive noise influence is close to a Gaussian electricity and circuits class 6 ppt noise or a Rayleigh noise according to the SNR.

Wireless communication technologies bring numerous benefits for smart grid applications including lower cost, more flexibility, easier installation, etc. In this paper, the performance of wireless local area network (WLAN) under impulse electromagnetic interference (EMI) in a substation is evaluated. Simulation results have demonstrated that the impulsive EMI causes more severe degradations compared with additive white Gaussian noise (AWGN), especially when the signal to interference plus noise ratio (SINR) is high. Although multiple-antenna based diversity schemes achieve better performance than the single-antenna scheme, the diversity gain is not sufficient to compensate for the performance loss caused by the impulsive EMI. Therefore, how to mitigate the impulsive EMI is essential for deploying WLAN systems in a substation. This paper also summarized conventional interference mitigation techniques, and their adaptability to the impulsive EMI. The analysis provides an insight to future research.

We present a system that both tracks human movements and detects falling in elderly and disable people. We applied Dynamic Time Warping (DTW) to recognize human activities in daily living. Seven different movements, stand, sit, walk, run, stand-to-sit, sit-to-stand and lyings were considered and recorded as reference database signals. Our system consists of two parts: transmitter and receiver. A … [Show full abstract] transmitter part is a device mounted at the user’s waist with a size of a pager case measuring 90x40x20 mm. A sensor used in this device is a 3-axial accelerometer (Hitachi H48C). The signals from the accelerometer are transmitted wirelessly to a personal computer in receiver part using Zigbee Pro 2.4GHz. DTW is used to match the signals from different behaviors online with the databases and electricity games online free classify the data to a known activity. Falls are detected with a rule-based approach, in which the signal values are over thresholds following by the lying activity. Thresholds are computed from the minimum and maximum value in each axis of acceleration in the reference databases. The experiment shows 98.6 percent accuracy in recognizing these behaviors and in detecting fall. Read more

Decentralized inverter control is essential in distributed generation (DG) microgrids for low deployment/operation cost and high reliability. However, decentralized inverter control suffers from a limited system stability mainly because of the lack of communications among different inverters. In this paper, we investigate stability enhancement of the droop based decentralized inverter control in … [Show full abstract] microgrids. Specifically, we propose a power sharing based control strategy which incorporates the information of the total real and reactive power generation of all DG units. The information 1 unit electricity cost in andhra pradesh is acquired by a wireless network (such as a WiFi, ZigBee, and/or cellular communication network) in a decentralized manner. Based on the desired power sharing of each DG unit and the acquired information of total generation, additional control terms are added to the traditional droop controller. We evaluate the performance of the proposed control strategy based on small-signal stability analysis. As timely communication may not be established for a microgrid with low-cost wireless communication devices, two kinds of analytical models are developed with respect to negligible and nonnegligible communication delays, respectively. Extensive numerical results are presented to demonstrate the system stability under the proposed control strategy with respect to different. Read more