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Author(s):  
V. A. Novobritsky ◽  
D. S. Fedosov

THE PURPOSE. This paper considers the problem of relay protection functioning when the current transformer reaches the saturation mode which is provided by transient processes.METHODS. MATLAB Simulink software environment allows reproducing the method of statespace representation by using structural blocks. The model is verified by comparison the time to saturation, obtained by calculation and according to the graphical data of the model. The separation of variables method extracts and graphically displays the investigated components.RESULTS. This paper reveals that applying the requirements of IEC 61869-2:2012 standard, which determines the worst combination of series of unfavorable factors for current transformers in transient mode, can influence a serious impact on the correct operation of relay protection based on current, reactance or differential principle of action. Saturation of the current transformer can lead to both negative results: false operation of relay protection devices and their failure.CONCLUSION. According to the results of the study, it was determined that the presence of a DC component in the primary short-circuit current has the greatest effect on the protection operation. The delays in the restoration of the RMS value of the short-circuit current reached up to 0.3 seconds, which is comparable with the response time of the second protection zones for microprocessor-based relay protection devices. The DC component of the primary current and the presence of residual magnetic induction of the current transformer provides the largest content of the magnetization current, the largest angular error and also the largest content of the second harmonic component in the secondary short-circuit current.


2022 ◽  
Vol 6 (4) ◽  
pp. 363-368
Author(s):  
Yu. S. Kozlova

Emergency modes (short circuits) in electric power system and equipment are the main technical cause of fires. However, it is not always possible to prove the involvement of a particular operating mode in a fire. The fire hazard can be due to three components: a fuel load, an oxidizer and an ignition source. Since overhead transmission lines are used in an open space, they are oxidized. The presence of a fuel load is confirmed by a fire. The source of ignition should be identified. The aim of the study is to develop an algorithm for assessing the fire hazard for short circuits in overhead transmission lines with 1000 V. The study was conducted using scientific analysis, physical experiment and simulation. The ignition source is due to the appearance of an energy source with parameters sufficient to ignite a fuel load. The probability of ignition in overhead line wires depends on the probability of occurrence of the short circuit itself  ( Qi (v1) ) , the probability of failure of protection devices  ( Qi (v2) ), and the probability that the electric current value in the event of a fault is in the range of fire hazard values (Qi(z)). The values of the first two components are determined on the basis of statistical data, taking into account the theory of reliability. The third component is based on the experiment results. The experimental studies made it possible to establish the ranges of fire hazard values for uninsulated aluminum wires of various cross-sections, thereby providing the possibility of calculating ( Qi (z). Using the data obtained and information about the nature of changes in short-circuit currents and performance characteristics of protection devices, depending on the line length, an algorithm for assessing the fire hazard for a short circuit was developed. The results make it possible to assess the fire hazard for short circuits in various sections of the electrical network, made by overhead transmission lines, and to establish the involvement of sparks generated by short circuits in a fire


Vascular ◽  
2022 ◽  
pp. 170853812110673
Author(s):  
Yusuke Sato ◽  
Kazushi Urasawa ◽  
Michinao Tan ◽  
Taichi Hayashi ◽  
Takashi Miwa

Objectives This study aims to report the efficacy and safety of new atherectomy methods using the Crosser system for calcified lesions in the common femoral and popliteal artery: the Crosser system supported by bended 0.014 wire (Crossbow) technique and retrograde approach of sheathless Crosser system supported by bended 0.014 wire (Rambow) technique. Materials and Methods This report describes a single-center, retrospective study. A total of 23 patients (mean ± SD age, 73 ± 10 years; 19 men) with symptomatic peripheral artery disease received the Crossbow technique and Rambow technique for treatment of calcified common femoral and popliteal disease; these patients were enrolled between October 2013 and October 2015. The primary efficacy outcome was acute technical success, defined as achievement of residual stenosis < 30% for stenting and < 50% for angioplasty or atherectomy. The primary safety outcome was assessed on the basis of angiographic complications. Results The Crossbow and Rambow techniques were undertaken in 100% and 17% of the patients, respectively. Acute technical success was achieved in 96% of the patients. There were two embolic events. Conclusion Crossbow and Rambow techniques could be effective atherectomy methods of calcified common femoral and popliteal disease. Regarding safety, embolic protection devices may be needed for our atherectomy methods.


2021 ◽  
pp. 11-17
Author(s):  
Mark V. Pestov ◽  
◽  
Til Diterich ◽  
Zhaskayrat E. Nurmukhambetov ◽  
Nurlan Kh. Ongarbayev ◽  
...  

This report presents the results of survey of a 46-kilometer section of the overhead line (OHL) powering the cathodic protection of the Bukhara – Ural Gas Pipeline within the Aktobe Region of the Republic of Kazakhstan. 7 kilometers of this section were previously equipped with bird protection devices (BPDs), which are now totally lost due to destruction of their fastening elements. Inspection of the 46-km section of this OHL has revealed deaths of 2 eagles (Aquilasp.), 1 Common Kestrel (Falco tinnunculus), 1 Black Kite (Milvus migrans), and 3 Greater Flamingo (Phoenicopterus roseus). The conclusion was made that the BPDs of this OHL needed renewal. It was also concluded that instead of OHLs laid along the pipeline route it was advisable to consider other options, including stations of cathodic protection fed from modular-packaged electrical power plants with self-contained micro-turbine units, such as used at the Beineu – Bozoy – Shymkent Gas Pipeline.


2021 ◽  
pp. 214-236
Author(s):  
Rinur H. Bekmansurov ◽  

This report presents the selected results of rare birds of prey studies in the Nechkinsky National Park (Udmurt Republic, Russia) 20 years after the first studies undertaken here by I.V. Karyakin in 1991–1996. The main efforts were directed to the study of the White-Tailed Eagle (Haliaeetus albicilla). At the same time, the identification of other rare species was made. The studies were carried out during short visits to the territory in 2016, 2017, 2019 and 2021. In the national park (NP), within the previously known breeding areas, 3 new nests were identified. They were 0.9–1.6 km displaced from the locations of the old nests found 20 years ago. A new breeding territory was found in the adjacent area near the border of the NP. Despite the incomplete study of the area, it is assumed to be 8-9 breeding areas in the national park, and 2–3 areas directly along its borders. The number of breeding pairs of eagles in comparison with the first half of the 1990s, according to the author, remains stable, and population increase, as happened on the Lower Kama in Tatarstan, has not been observed here. Eagles nest on large, old-growth pines and larch trees, with a distance of 130–530 m deep into the forest from the outer edge. The distance to the Kama River is 0.68 km on average (0.13–1.3 km, n=4). The minimum distance between the nearest neighbors in the Kama valley, unregulated by the reservoir, is currently 3.6 km, the average (n=3) – 3.9 km. Eagles breed occasionally on and off. No reproduction was recorded for 2–3 years. The period of egg laying extends for a month from the beginning of March to the beginning of April. The death of young birds on 6-10 kV power lines was revealed, as a result, the owners were obliged to equip the power lines with bird protection devices. White-Tailed Eagle nestlings were ringed with colored rings. Two repeated observations were obtained from the lower reaches of Kama. The Greater Spotted Eagle (Aquila clanga) continues to inhabit the National Park, which is confirmed by the meetings of adult birds. There has been two-three times population of the Peregrine Falcon (Falco peregrinus) in comparison with the first half of the 1990s. Breeding of this falcon was found on 2 territories with a distance of 16.5 km between them.


2021 ◽  
pp. 42-68
Author(s):  
Elena P. Shnayder ◽  

In September 2021, 126 km of 6-10 kV power lines were surveyed in Altai Kray, Russia. The survey encompassed different types of habitat from pine forests to the foothills of Altai mountains. Out of 126 km, 27.94 km of power lines were equipped with bird-protection devices to prevent bird death from electrocution. We uncovered 515 cases of bird death on unsafe lines. Raptors make 21% and endangered species – 1.94%. The density of dead birds was equal to 5.6 ind./km of non-safe power lines, and of raptors – 1.18 ind./km. The observed damage to the ecosystem was estimated as 6.1 million of Rub (equal to $83 350 or € 73 600), and the damage calculated per one electric pole was 3 925 Rub. The estimation of the death rate of birds on the observed length of power lines through the whole migration and breeding seasons makes 8.63 ind./km. Approximation to the presumptive total length of bird unsafe power lines in the Altai Kray makes 50 700 birds possibly die every year in the region from April till October. The highest level of bird mortality was observed on power lines stretching through open undisturbed habitats (i.e. steppe biotope). We also noted 2.9 times higher mortality on push brace poles compared with intermediate ones for all species, and 4.9 times higher for raptors only.


Author(s):  
A. Lovska ◽  
O. Fomin ◽  
D. Skurikhin ◽  
V. Bondarenko

Maintaining a high level of maintenance of electrical equipment in passenger cars requires research in the field of improving methods and means of technical diagnostics. Electronic devices for automatic control and protection, which are located in the switchboard of the car, are one of the most critical elements in the electrical equipment system, ensuring its reliable, efficient and safe operation. If the automatic adjustment and protection devices are out of regulation during operation, the voltage and current in the electrical equipment network may exceed the permissible level, which leads to the failure of electricity consumers, a battery and a generator. In addition, the semiconductor devices themselves are very sensitive to short-term overloads, in which, even with minor overloads, a breakdown or breakage of the conductive layer occurs. Modern trends in the development of passenger car fleet indicate a sharp increase in the complexity of the element base of cars. This mainly concerns the electrical systems of cars, where all the functions of control, monitoring and diagnostics are performed by electronics. Maintaining a high level of service for such systems requires research in the field of improving methods and means of technical diagnostics. For these purposes, the authors have developed a method for constructing optimal control and diagnostic tests, which is based on a combinatorial approach. The method is easily implemented on a computer.


Author(s):  
Alexandr Neftissov ◽  
Andrii Biloshchytskyi ◽  
Olzhas Talipov ◽  
Oxana Andreyeva

A study of the functioning of reed switches under the influence of a magnetic field created by a current in a conductor in a transient mode with the presence of an aperiodic component has been carried out. A well-known method for determining current using reed switches was implemented. At the same time, it was determined that the originally formulated method did not give the required result within the limits of errors. This is most likely due to the peculiarities of the mechanism of movement of the reed switch contacts. Alternatively, the measurements were taken to take the return currents instead of the pick-up currents and the time between the return times. They are more stable. Simulation is performed, experimental determination of the value of surge current by measuring time is carried out. The main element of the created installation was the power transformer coil with low active and high inductive resistance. As part of the study, the reed switches were placed in a magnetic field with an aperiodic component, as in the transient mode. This study will show the applicability of reed switches for the construction of relay protection devices that will not need current transformers to obtain information about the primary current in the conductor. In the course of the research, it was found that the error in determining the magnitude of current was no more than 10 %. Using microprocessors, it is possible to build relay protection devices with a speed of up to 20 ms. This result makes it possible to build new devices. Since in the well-known developments, it was only said about determining the magnitude of current in a steady state. When building relay protection devices on reed switches, without using current transformers, it will be possible to build backup protections that duplicate not only the devices themselves, but also the primary measuring transformers with other sensitive elements. This will improve the reliability of the power supply.


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