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Marius Valerian Paulet, Alexandru Salceanu, Catalin Lazarescu, Ovidiu Bejenaru, B. D. Alistar
Study Upon the Influence of Human Body Torso Stance on the Inductive Coupling

The paper presents a study on the relevance of the relative position of the human trunk to the plane of the supporting pylons of various Overhead High Voltage Power Lines (OhHVPL), from the perspective of currents induced by the generated magnetic field. A homogenous model of the human body that considers the trunk as a cylindrical ellipsoid has been developed in CST Studio software. After necessary theoretical brevity, the results obtained by simulation for the loop currents along the perimeter associated with the large axis of the transversal section of the trunk and that associated with the small axis are presented and commented. The simulations have been performed for 5 relative positions (0°, 30°, 45°, 60°, 90°) of the human trunk with respect to the plane of the network supporting pylons and for three different types of symmetric, c double three-phase networks (110 kV and 640 A, 220 kV and 900 A, 400 kV and 1500 A). The obtained results make it possible to formulate recommendations on the reduction of exposure to magnetic fields. Also, more refined approaches might be further prepared to take into account cumulative aspects of short-term human exposure to Extreme Low Frequency (ELF) electrical and magnetic fields.

Ovidiu Bejenaru, Catalin Lazarescu, Marius Valerian Paulet, Alexandru Salceanu
Study Upon Specific Absorption Rate: Far Field Source Outside and Subject Inside the Building

It is well known that the biological and health effects of electromagnetic fields (EMF) are an up to date theme and the associated impact should be taken into consideration. Aiming to estimate these biological effects, an essential item is the accurate estimation of the human exposure to different types of non-ionizing electromagnetic sources. The evaluation of human exposure is performed by determining the currents distributions inside the biological organs or tissues, modeling the different acting mechanisms and understanding the effects developed in living beings by various exposure scenarios. Radiofrequency field absorption in homogenous and heterogeneous biological tissues is computed by using analytical and/or numerical methods. In this paper we have determined by simulations with CST Suite Studio software, the values of specific absorption rate mediates on 10 grams of tissue , SAR Max (10 g), in case of a human body exposure to electromagnetic field generated by a far field source. Here proposed scenario involves the human body located inside the building, in empty room. We have used our previously developed human body 3D model having ellipsoidal cylinder geometry. The determined SAR values have been also compared with those recommended by the International Commission on Non-Ionizing Radiation Protection (ICNIRP) and IEEE Standards for Safety Levels (2005).

Honghui Li,Wenhui Cao, Zengmin Wang, Jinjin Li, Qing He
Microvolt Josephson Voltage Standard Using a Dual-Channel Programmable Array Chip Developed at NIM

Previously a differential programmable Josephson voltage standard (DPJVS) has been developed for precision ultra low-voltage measurement of microvolt (µV) level at NIM. In this paper we present an updated technology for microvolt Josephson voltage standard (MJVS) which uses a dual-channel Josephson array chip with NbSi barrier developed at NIM. It is a new type device to build two symmetric paths of microwave irradiation for differential frequencies applying to a pair of channels of Josephson junction array. This new approach can efficiently simplify the complicated DPJVS system, which has two cryogenic systems, more expensive devices and is more difficult to operate. Based on it, a series of quantum-accurate microvolt voltages are achieved with uncertainty less than 1 nV, tens of times more accurate than the conventional technique. And the relevant precision measurement system has been established for calibration purpose. For practical application, a nanovolt meter has been successfully measured under the 10 µV range. Besides this, an improved 10 V PJVS is in progress to be improved in range and resolution when combining with the new standard based on the new dual-channel Josephson array chip.

Guan Ze-xin, Li Wen-qiang, Zhao Yan, Ma Xue-feng, Sun Xiao-yan, Wang Da-long, Yan Hongrui
No oscillator output frequency counter automatic test equipment

Frequency counter is an instrument for measuring frequency signal. According to whether the internal crystal oscillator is output or not, it can be divided into the oscillator output frequency counter and no oscillator output frequency counter. For the detection of non crystal oscillator output frequency counter, manual verification method is time-consuming and laborious. In order to realize automatic operation and improving the quality and the efficiency of verification, a research on design of the automatic system is carried out. On the basis of verification regulation, a automatic test equipment of no oscillator output frequency counter is designed, which can achieve automatic verification of the boot feature, frequency reproducibility and accurate frequency.

Nejc Klevišar, Dušan Agrež
Detecting cracks on graphite commutators using estimated amplitude of resistance

In this paper, the method for detecting cracks on graphite commutator with resistance measurement is described. Resistance is measured with four-point resistance measurement method when commutator is rotated. Result of measurement is surface resistance profile of graphite from which a cracks can be recognized. Information of the crack on the commutator graphite surface is hidden in the amplitude behaviour of a strongly distorted signal. Since the period of the amplitude changing is not constant the interpolation DFT algorithm is used first to estimate the current period along the turn of the rotated commutator around its axis and upon this the amplitude of the fundamental component. The amplitude estimation is achieved with only one DFT coefficient at i = 1 for an almost coherent measurement interval of one period. Behaviour of the amplitude changing shows that the commutator with crack has specific increase of the amplitude around peak value and frequencies of the amplitude distribution can be used for the reliably checking of the crack presence.

Daniel Belega, Dario Petri, Dominique Dallet
Contribution of Interharmonic Component on the Interpolated DFT Frequency Estimator

This paper investigates the contribution to the sine-wave frequency estimator returned by the interpolated discrete Fourier transform (IpDFT) algorithm of a small amplitude interharmonic component located at least one bin apart the unknown frequency. An analytical expression for the frequency estimation error is derived assuming that a maximum sidelobe decay (MSD) window is employed and its accuracy is verified through computer simulations. Based on the derived expression some useful remarks are finally drawn.

A. Mariscotti, D. Giordano
Electrical Characteristics of Pantograph Arcs in DC Railways_ Infrastructure Influence

Electric arcs are an unavoidable by-product of current collection by sliding contact in electrified transportation systems. Electric arcs are transient phenomena with implications for PQ measurements and wearing estimation and prevention of the sliding contact and catenary. Besides being heavily influenced by mechanical characteristics and material properties, their electrical characterization encompasses spectral properties and the influence of train and traction line circuits and relative position of infrastructure elements. This paper identifies the influence of such electrical and system characteristics onto the spectral signature of electric arcs for DC railways.

Andrea Mariscotti
Discussion of Power Quality Metrics suitable for DC Power Distribution and Smart Grids

PQ metrics for DC distribution systems are considered and reviewed with the objective of covering typical PQ phenomena, of finding similarity with the more proven indexes for AC systems, identifying the most promising approaches. Both time and frequency domain methods are considered, with emphasis on compact implementation and immediacy of output quantities. Behaviour and performance are verified against a first set of data representing the line voltage of a DC 3 kV railway system.

Xuefeng Ma, Wenqiang Li, Mei Yang, Xinyan Wang, Jianbo Liu, Shang Wang, Zhixiong Chen
Calibration of current measuring network for wet contact of leakage current tester

In this paper, the transfer characteristics of current measuring network for wet contact are determined, the current measuring network is calibrated with the method of high frequency voltage source. It has been verified that the measurement results consist with the requirements of IEC 61010-1.

Diego Cavaliere, Alessandro Mingotti, Gaetano Pasini, Lorenzo Peretto, Roberto Tinarelli
MV Surge Arresters Monitoring Using Drone Technology

This paper presents a pole-mounted measurement system to detect the leakage current of surge arresters. Such a current is a paramount index to determine the aging of the surge arrester. Moreover, all the measurements acquired by the developed pole-mounted system are collected using drones. This way, in every drone flight a huge amount of data can be gathered from the grid. Hence, improving and fastening the power network monitoring and maintenance.

Page 204 of 977 Results 2031 - 2040 of 9762