Monthly Archives: February 2021

Influence of Synchronized Measurement Errors on the Results of Identification of the Transmission Line Parameters


The parameters of transmission lines, as a rule, are determined by reference data, but during the operation, it might vary essentially from the actual data. There are noted the reasons for the parameters’ modification. This paper explains the opportunity of parameter identification based on the synchronized measurements during the operation of the transmission line. The methods of parameter identification can be classified by various criteria. The diagram of classification was elaborated for the first time. Transmission lines can be represented in the form of quadripole and the Т- and П-forms equivalent schemes, so, applying only the current and voltage synchronized measurement on both ends it is possible to obtain passive parameters of the line. There are presented final formula of six most effective methods for parameter identification of the transmission lines. All analyzed methods were verified with the models of real transmission line. There were compared the results of all proposed methods: the relative errors of calculation for all mentioned methods are less than 1%. The obtained results show the high accuracy of parameter identification for the proposed methods. The influence of measurement errors upon the values of parameters’ results was analyzed in this work. The main contribution of this paper lies in the classification of the methods of transmission line parameters identification and in the research of influence of measurement errors on the results of the parameter identification for transmission lines. images

Wireless Remote Control for the Anti-Hail Missiles Launch Ramp Positioning System


This paper describes a wireless remote control designed for the positioning system of the launching pad of anti-hail missiles used by the Romanian Anti-Hail System. The remote control operates in the ISM band of 2,4 GHz and was successfully tested on a simplified, small size, experimental model of the actual launch ramp. The remote control allows the operator to position the launch ramp on two axes, azimuth, and elevation, and fire the missiles, using momentary push buttons. A 16×2 characters LCD display indicates the current position of the ramp, and the presence and the type of the anti-hail missiles loaded on the ramp. The remote control was built using Arduino microcontrol-lers and radio frequency transceivers and uses two separate one-way transmitter-receiver radio channels. The simplified experimental model of the launch ramp features the main functional characteristics of the actual ramp and was de-signed and built for the purpose of testing the remote con-trol, due to no access to the actual ramp, along with the in-tention of using it to train the Local Unit operating person-nel during the off-season time. When designing and building the remote control and the experimental model of the ramp it was taken into consideration an easy implementation on the actual ramp, with minimal modifications. images

The Use of Helmholtz Coils Designed for 50 Hz at Higher Frequencies


Helmholtz coils (HC) are used in order to generate and control uniform magnetic fields for a variety of re-search applications. They can be easily constructed and their fields can be easily calculated. This makes them espe-cially useful in calibrating magnetic field sensors. Such a calibration system with large Helmholtz coils (1x1m) can be found in ICMET Institute, designed to operate only at a frequency of 50 Hz. There has recently been a request for the calibration of several measuring sensors operating at frequencies up to 10 kHz used in industrial applications such as induction hardening of metal parts. The paper aims to determine the conditions under which this low frequency HC system can be used at frequencies at least 100 times higher. The first part of the paper describes a theoretical analysis on the volume confining the space where the mag-netic field components have a predetermined deviation (a 2% threshold) from the center of the HC system followed by a comparison with a 3D FEM simulation and measurement of HC field. The second part describes the identification of the HC parameters at higher frequencies and the resonant methods used to achieve the excitation power required at these frequencies. images