Transient impedance of grounding system with impulse superimposed sinewave

Investigating the transient performance of grounding systems subject to lightning (impulse or impulse superimposed sinewave) is valuable for protecting the power system and maintaining the system operation. In this work, the grounding system's impedance is computed when an impulse superimposed sinewave is applied to the grounding grid's proposed lumped circuit and grounding system can be simulated as an inductance in series with resistance, and all of them are in parallel with capacitance based on Thione's assumption. Several variables were investigated to study their effects on the grounding system's behavior. The variables were the soil resistivity, soil permittivity, main wire length, grid conductor radius, grid side length, grid configurationand its mesh number. The grounding system configuration varied between square and rectangular shapes, which connects to the protecting rod via the main wire conductor. A 3.69 kA peak of impulse current was applied to avoid soil ionization. The results indicated the performance of the grounding system when subjecting to impulse current.

Design of Ultrawide Bandwidth Electromagnetic Wave Absorbers with Square Patch Frequency Selective Surfaces with Different Geometries

A reliable and efficient numerical method is presented for the design of broadband absorbers, fabricated by layering two square patch-frequency selective surfaces (SP-FSS) with different geometries on a grounded dielectric substrate. The circuit parameters of the inductance and capacitance of the SP-FSS were retrieved using the strip wire conductor model. Due to the high capacitance and low inductance of the SPFSS, a nearly constant resonance frequency (<i>f</i>₀ = 37 GHz) is observed, irrespective of patch size at a given unit cell periodicity of 7.5 mm. For the SP-FSS, the circuit is capacitive below <i>f</i>₀ and inductive above <i>f</i>₀. For a grounded substrate with a quarter wavelength thickness, however, the input impedance is inductive below <i>f</i>₀, resulting in impedance matching over a wide frequency range, with the controlled FSS resistance matched to the free-space impedance. The double-layer absorber was designed by optimizing the surface resistance and layer thickness of two SP-FSSs with different geometries, and demonstrated a 10 dB absorption bandwidth of 6.1−41.4 GHz with a total thickness of 5 mm, which is equal to the theoretical limit. A test sample was prepared by screen printing method, and the free space measurement demonstrated a wide-bandwidth absorption result (4.7−40.0 GHz for −10 dB reflection loss) with a small total thickness (5.4 mm). The simulation and experimental results strongly validated the SP-FSS for the design of wide bandwidth electromagnetic wave absorbers.

Primary gas discharge transducer and its application

The aim of this study is to develop a high-speed fault transducer and, based on it, to create an automated system for monitoring and repairing faulty insulation of winding wires in electrical equipment. The fault transducer under development is based on a gas discharge process that occurs between a high-voltage electrode and a grounded wire conductor in a damaged insulation segment. Oscillographic measurements show that there is a complex signal that appears on the fault transducer when a damaged insulation segment is passed through it. The basic patterns of electrodeposition of dielectric films onto metals were determined. The conditions of this process were optimized. The features of the above-mentioned signal that can be used to monitor the number of faults and lengths of damaged segments, as well as the features of the deposition of dielectric films onto metals were justified. Based on these features, a faulty wire insulation repair process was developed and can be controlled.

Application of Copper Cladding Aluminum Composites in UHV Portable Earthing and Short-circuiting Wires

Aiming at the heavy weight and inconvenience when carrying and installing copper earthing wires on the UHV transmission lines, in this paper, we present the use of copper clad aluminum(CCA) composite materials as a lightweight method for UHV earthing wire conductor. Theoretical calculations and tests of the fusing current in a short time for copper and CCA material are conducted. The results show that the theoretical value of the earthing wire conductor's fusing current corresponds with the test value on condition of the conductor cross section greater than 4mm2 as well as fusing time less than 1.5s. The CCA-10 earthing wires get 36.2% weight reduction compared with copper wires.

ANALISIS RESISTANSI COIL KAWAT TEMBAGA TERHADAP PERUBAHAN SUHU SANGAT RENDAH SEBAGAI RANCANG DASAR PENGUKURAN SUHU RENDAH

The resistance of a wire conductor depend of the wire material. Copper wire formed into a coil shape an effective form to produce a large resistance. Copper wire resistance influenced bytemperature about it. Coil of copper wire has a good response at low temperature changes produced by liquid nitrogen. This response is shown by the index value determination (R2 = 0.999) which is close to the value 1,that means changes in temperature approaching a linear response to changes in a voltage. The results can be used as a basis for the design of the low-temperature measurements cheaper

NUMERICAL SIMULATION OF THE HEAT CONDUCTION IN ELECTRICAL CABLES

The modelling of the heat conduction in electrical cables is a complex mathematical problem. To get a quantitative description of the thermo‐electrical characteristics in the electrical cables, one requires a mathematical model for it. It must involve the different physical phenomena occurring in the electrical cables, i.e. heat conduction, convection and radiation effects, description of heat sources due to current transitions. Since the space in mobile systems is limited and weight is always reduced, wire conductor sizes must be kept as small as possible. Thus the main aim is to determine optimal conductor cross‐sections for long standing loads. In this paper we develop and validate a set of mathematical models and numerical algorithms for the heat transfer simulation in cable bundles. The numerical algorithms are targeted to the two‐dimensional transient heat transfer mathematical models. Finally, a validation procedure for the coefficient validation of the differential equations is carried out. Results of numerical experiments are presented.