Science and Technology
A.A. Kryuchkov, Cand. Sc. (Chemistry), Leading Research Scientist, OJSC VNIIKP;
M.A. Nikolaeva, Junior Research Assistant, OJSC VNIIKP;
T.A. Stepanova, Research Scientist, OJSC VNIIKP;
V.A. Fedorova, Junior Research Assistant, OJSC VNIIKP;
M.Yu. Shuvalov, Dr. Sc. (Engineering), Division Manager — Director of Research Area, OJSC VNIIKP
Comparative study of thermal ageing of peroxide cross-linkable polyethylenes for insulating medium-voltage cable
The paper presents the results of a comprehensive study into the thermal ageing of six LDPE-based peroxide cross-linked insulation compositions. The thermal ageing tests were performed on samples protected against a direct contact with ambient oxygen. It is stated that under the selected test conditions the polymer oxidation is the primary process causing changes in many practically important properties of the materials. It is shown that the value of elongation at break is inversely proportional to the concentration of carbonyl groups developing during the polymer oxidation. This dependence is common for the data obtained for all tested material samples, test temperatures and test durations and can be used to assess the physical state of cross-linked LDPE with the help of the IR-spectrometry method. The catalytic effect of microscopic foreign particles on the polymer oxidation is pointed out. The results of the comparative analysis of the changes in the main critical characteristics of the tested compositions are given. The authors suggest working hypotheses about the possible mechanism of medium and high voltage cable failure due to heat effect. The importance of testing full-scale cable specimens in addition to insulation material sample tests is explained.
polyethylene, thermal ageing, IR-spectrometry, thermal analysis, mechanical properties, electrical properties, oxidation, activation energy.
V.N. Egorov, Dr. Sc. (Physics and Mathematics), Leading Research Scientist, FSUE «VNIIFTRI»;
Le Kuang Tuen, Graduate Student, Irkutsk National Research Technical University;
Ya.O. Zuev, Leading Engineer of JSC «OKB KP»;
V.V. Kostromin, Cand. Sc. (Engineering), Chief Specialist;
B.S. Romanov, Cand. Sc. (Physics and Mathematics), Head of Laboratory, Test Center of JSC «OKB KP»
Measurement of low dielectric losses of polymer materials in ultra-high frequency band
The article deals with the measurement of specific dielectric constant and loss-angle tangent of low-absorption dielectric materials at ultra-high band frequencies in a high-quality coaxial resonator with a “shortening” capacitive gap. The resonator has intrinsic Q-factor over 6850 at a frequency of 550 MHz and is capable of measuring disc specimens of insulating materials with a standard diameter of 50 mm, thickness from 0.5 to 2.1 mm and low. The high Q-factor of the resonator is achieved by lowering the microwave energy loss due to radiation through the window for inserting the measured specimen into the resonator.
The characteristics of the measurement unit with this resonator and the measurement results of the dielectric parameters of certain insulating materials are presented.
coaxial resonator with a shortening capacitive gap, dielectric capacitance, loss-angle tangent, insulating materials.
M.A. Boev, Dr. Sc. (Engineering), Professor, National Research University (MEI);
Ye Kyaw Min, Post-Graduate Student, National Research University (MEI)
Assurance of mechanical parameter requirements for optical cables intended for burial in a tropical climate
Present-day designs of ОГЦ and ОГД optical cables used for laying in the ground are presented. The cables are manufactured in accordance with the requirements of TU 3587-001-58743450–2005. Technical requirements for admissible tensile stress applied to the cable are considered in comparison with the experimental test results of ОГЦ-16А-7, ОГД-4×4A-7, ОГЦ-32А-7, ОГД-4×8А-7, ОГЦ-48А-7, ОГД -6×8A-7, ОГЦ-16А-20, ОГД-4×4A-20, ОГЦ-32А-20 and ОГД-4×8А-20 cables. The construction design of these optical cables is analyzed. Experimental results of the optical fiber attenuation rate changes under the exposure to mechanical factors are given; the admissible tensile stress is stated.
attenuation, optical cable, optical fiber, tensile stress.