Abstract This paper presents the study of deformations and Von-Misses stresses of the main shaft system during opening and closing operations of a rotary SF6 load break switch (LBS). The shaft consists of three axially connected parts made of steel where components are on ground potential and of plastic material, which is on high potential. The insulating shaft carries three rotating knife-blade contacts for the three phases. Static deformation of the insulating shaft is calculated by applying a defined torque between the two ends of the shaft. The results allow deducing the dynamic deformation. Maximum values of Von-Misses stresses are located at the geared connection between the plastic and the steel shaft. The rotation of the shaft system is measured synchronously by two optical rotary encoders in the front and rear sides of the LBS. The results confirm the twisting of the shaft system and provide its elastic deformation values. Travel curves obtained on both side of the LBS show different courses with respect to overtravel and rebound. Discrepancies can be explained by the deformation of the main shaft due to the acting forces, whereas manufacturing tolerances resulting in loose have a certain contribution.
Abstract The breaking capacity of a medium voltage (MV) rotary SF6 load break switch (LBS) can be improved by incorporating permanent magnets into the stationary contacts. The magnetic field is intended to blow the switching arc root towards a recessed space at the stationary contacts thereby preventing reignition of the arc after current zero. Making and breaking tests of load current 630 A were performed comparing the switching performance of load break switches equipped without a permanent magnet, with a ferrite and with a neodymium magnet. The impact of different polarity arrangements of the magnets in the three phases is also considered and analysed. In order to understand the arc behaviour caused by the effect of permanent magnet, arcing times and arc voltage were measured and evaluated. The results show that the arc voltage depends on the direction of the electromagnetic force, which is determined by the phase current direction but also by the polarity of the magnets. When the force is directed towards the recessed space at the stationary contacts, the arc voltage is notably higher than in the case where the arc is blown in the opposite direction. The higher arc voltage is a reliable indication that the length of the arc is increased, which significantly reduces the risk of both thermal and dielectric breakdowns after the first current zero. The consequences are noticed first in the reduction of the number of missed current zeroes and second in shorter minimum arcing times. An adverse arrangement of the magnet polarity in the three phases increases the number of missed current zeroes.
Abstract This paper presents the design and development of a distributed measurement system for measuring pressure in high voltage circuit breakers (HV CB) and other switching apparatuses, during no-load operations. Instead of using traditional pressure transducers which require significant installation space, additional data acquisition cards and often demand for complex wiring, an in-house solution of pressure measurement is proposed. The system consists of miniature sensors, accompanied with a suitable amplifier, microcontroller unit and communication module, which may be distributed inside the interrupter unit in convenient locations. Due to the fact that the measurement values are transmitted digitally, measurement noise is significantly reduced while the wiring of the system is additionally simplified. The proposed measurement system is tested using two different interrupters (HV CB and a load break switch). The experimental results have demonstrated that the developed system is applicable, accurate, cost-effective, flexible and simple to use.
The breakdown voltage during interruption of capacitive currents is defined by two physical quantities: the electric field and the gas density field, which are calculated in different calculation domains and using different mashes. In order to calculate the breakdown voltage, it is necessary to map these two mashes and calculate the ratio density/electric field in every calculation point. The straightforward solution is to pair each density cell with the nearest cell from the electric field mesh, based on their coordinates. Although this solution gives good results, it is very time consuming. Therefore, this paper presents a new approach for mapping of two meshes based on the algebra of fractal vector, so called Bosnian algebra. This approach does not search the meshes for the closest pair based on the coordinates of each point, but instead uses only the assigned cell indexes and simple fractal operations to determine the neighboring cells. This way, the search for the nearest pair is much more efficient and faster.
This paper focuses on the optimization of the design of high voltage transmission lines in order to reduce the negative impact of electric and magnetic fields. Within this paper the results of measurements of electric and magnetic fields near 400 kV transmission line were presented. Measurements were performed in the middle of the range between two towers, because at this point transmission lines are closest to the ground. In order to make better validation of the used calculation models of electric and magnetic fields, measurement of temperature, pressure, humidity and height of particular transmission lines in the middle range, were performed simultaneously. The values of current and voltage on the transmission line, at the time of measurement of the fields, are also given. Based on the measured values of electric and magnetic fields, validation of calculation was performed. This paper also contains a brief comparative analysis of regulations on non-ionizing radiation of power facilities that are in use in some European countries, as well as recommendations of the International Commission on Non-Ionizing Radiation Protection (ICNIRP). Calculation of electric and magnetic fields of different configurations of 400 kV transmission line, were performed in order to find optimal solution in terms of reducing the negative impact of electric and magnetic fields of high voltage transmission
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