SF6 Density Research Articles

The Machine Vision Dial Automatic Drawing System—Based on CAXA Secondary Development

Whether the pointer recognition of an SF6 (sulfur hexafluoride) density controller is correct or not is directly related to enterprise security. Therefore, a pointer recognition system that is highly efficient, precise, and secure is required. In this paper, we set up a detection platform for efficient detection of pointer readings. To detect the pointer with high accuracy, we propose a dial pointer angle detection method based on OpenCV that obtains high-precision dial pointer angle information. We then use Socket communication to transmit the dial pointer information to the secondary development program. Finally, we use the ObjectCRX development software package based on Visual Studio 2015 to quickly access the CAXA electronic drawing board graphics database, carry out secondary development of the CAXA electronic drawing board 2021, and comprehensively apply various functions to draw the overall outline of the dial. Finally, we read the dial pointer angle in order to draw the current test product dial CAD drawing. After verification, the average error rate of pointer angle recognition is 0.69°, which is much lower than the enterprise standard of 2.7°. Based on machine vision technology, we researched and designed an SF6 density controller dial automatic drawing system, and after many tests, the system runs stably and the accuracy meets the needs of enterprises.

Multi-pass Differential Photoacoustic Sensor for Real-Time Measurement of SF6Decomposition Component H2S at the ppb Level

We designed and implemented a photoacoustic (PA) sensor for H2S detection in SF6 background gas based on a multi-pass differential photoacoustic cell (MDPC) and a near-infrared distributed feedback (DFB) laser. In the MDPC apparatus, two resonators with identical geometric parameters were vertically and symmetrically embedded. The differential processing algorithm of two phase-reversed signals realized the effective enhancement of the PA signal and suppressed the flow noise in the dynamic sampling process. In addition, the λ/4 buffer chamber in the MDPC was utilized as a muffler to further reduce the flow noise and realize the dynamic detection of H2S. The collimated excitation light was reflected 30 times in a multi-pass structure constituted of two gold-plated concave mirrors, and an absorption path length of 4.92 m was achieved. Due to the high gas density of SF6, the relationship between the signal-to-noise ratio (SNR) and the gas flow was different between SF6 and N2 background gases. The maximum flow rate of the characteristic gas components detected in the SF6 background is 150 standard cubic centimeters per minute (SCCM), which is lower than 350 SCCM in N2. The linearity property was analyzed, and the results show that the sensitivity of the sensor to H2S in the SF6 background was 27.3 μV/ppm. With the structure, parameters, temperature, gas flow, and natural frequency of the MDPC been optimized, a minimum detection limit (MDL) of 11 ppb was reached with an averaging time of 1000 s, which furnished an effective preventive implement for the safe operation of gas insulation equipment.

OpenCV-based SF6 density controller dial pointer angle recognition

To solve the problems of the low efficiency and poor accuracy of the manual detection in the factory inspection of the SF6 density controller, this paper proposes an SF6 density controller dial pointer angle identification method. First, the image of the dial pointer at a specific position is acquired according to the working characteristics of the SF6 density controller. The center and radius of the contour circle inside the scale line in the dial are extracted using the Hoff gradient method and the image is coordinate transformed using this parameter. Then the coordinate-transformed image is pre-processed. And finally, the threshold of the image after pre-processing is traversed and the length is used to characterize the pointer angle through the correspondence between the scale line and the angle. The angle of the pointer is characterized by the correspondence between the scale and the angle using the length. This paper uses Python and OpenCV vision library to complete the algorithm and through experiments, the algorithm can achieve high precision pointer angle recognition.

Simulation research on the pre-strike characteristics of SF6 circuit breaker

The pre-strike duration of SF6 circuit breaker closing is one of the indicators to measure the ablative state of contacts, obtaining the pre-strike characteristics of SF6 circuit breaker closing is very important to evaluate the electrical life state of circuit breakers. In this paper, the simulation model of the electrical and fluid coupling simulation of the 110kv SF6 circuit breaker is established, and the pre-strike characteristics of the closing process are studied. The results show that the maximum point of the synchronous midfield is always on the surface of the static arc contact. The density of SF6 on the arc-extinguishing chamber is almost constant; the pressure output of the pressure chamber has little effect on the pre-strike voltage curve. Under the phase voltage of 110kv voltage, the duration of the circuit breaker pre-strike duration is 0.9054ms, which is close to the measured value. Results can provide the basis for the actual life circuit life evaluation.

Development of SF6 Gas Pressure Prediction Device in Substation

SF6 equipment has leakage due to various reasons. The longer the equipment operates, the more serious the leakage is. When the equipment gas leaks to the set air replenishment value, the air replenishment alarm signal will be sent. It can be seen from the SF6 gas temperature pressure relationship table that the temperature change has a great impact on the pressure value. Although the equipment popularizes the SF6 density meter or SF6 density relay with temperature compensation, the compensation system needs to achieve temperature compensation through a long time, resulting in the distortion of the pressure value counted by the operation and maintenance personnel. Therefore, the temperature difference between winter and summer is large, and more alarm signals are obtained. At this time, there are great potential safety hazards in air replenishment. This paper introduces in detail a SF6 gas leakage prediction device in substation, which can effectively solve the above problems in substation.

Design and demonstration of a wireless sensor network platform for substation asset management

A key challenge for distribution and transmission system operators is to relate the retrofitting of monitoring systems to support asset management aligned with the continuity of service within the electrical network. The research within this study demonstrates how a Smart System Integration approach, utilising a wireless sensor network (WSN), can provide a low cost and scalable sensor platform for in situ sensing of SF6 within substations. In this study, the design and manufacturing stages of an ultra-low power WSN are outlined. The WSN is evaluated within a high-voltage laboratory and deployed within a 400 kV substation. Results indicated that the system can reliably transmit data within a noise environment, recover when there is a mote failure without data loss, can operate on batteries for 1.5 years or 5 years taking 1 SF6 density measurement every 60 or 300 s, respectively. The findings of this research demonstrated the advantageous features of WSNs, namely low cost, rapid deployment, reliable and secure data transfer, adaptive and scalable sensor platform.

From the editors' desk

This issue has four articles, the first of which is "Density Monitoring of High- Voltage SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> Circuit Breakers" by Peter Cheetham and Ali Hellany of the School of Computing, Engineering and Mathematics, University of Western Sydney, Sydney, Australia, and Steven Jones of TransGrid, Australia. The article analyses different aspects of density monitoring which need to be considered to successfully retrofit a HV SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> circuit breaker with density-monitoring equipment. A condition-monitoring network needs to be able to provide the user with real-time information of the circuit breaker's condition, as well as be able to cope with the installations of new condition-monitoring equipment. A sampling rate of 30 minutes allows for accurate representation of the SF6 density level within the circuit breaker while reducing the number of measurements. Filtering the density measurements between 10 pm and 4 am eliminates fluctuations caused by ambient conditions. The filtering process allows for the early detection of SF <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sub> leaks that would have been almost impossible to detect from looking at the total density measurement.

Electron attachment toSF6and lifetimes ofSF6−negative ions

We study the process of low-energy electron capture by the SF6 molecule. Our approach is based on the model of Gauyacq and Herzenberg [J. Phys. B 17, 1155 (1984)] in which the electron motion is coupled to the fully symmetric vibrational mode through a weakly bound or virtual s state. By tuning the two free parameters of the model, we achieve an accurate description of the measured electron attachment cross section and good agreement with vibrational excitation cross sections of the fully symmetric mode. An extension of the model provides a limit on the characteristic time of intramolecular vibrational relaxation in highly-excited SF6-. By evaluating the total vibrational spectrum density of SF6-, we estimate the widths of the vibrational Feshbach resonances of the long-lived negative ion. We also analyse the possible distribution of the widths and its effect on the lifetime measurements, and investigate nonexponential decay features in metastable SF6-.

THEORETICAL, EMPIRICAL AND EXPERIMENTAL ELECTRON AFFINITIES OF SF6: SOLVING THE DENSITY FUNCTIONAL ENIGMA

We postulate that the adiabatic electron affinity of SF6 is 2.40(10) eV, obtained from the photodetachment onset, 3.2(1) eV and a rearrangement energy of 0.8(1) eV. This eliminates the perceived "SF6 density functional enigma". All of the experimental electron affinities are evaluated and 14 significantly different values selected to construct empirical anionic Morse potentials. These values are (in eV): 2.40(10) 2.20(10), 2.00(10), 1.80(10), 1.60(10), 1.20(10), 1.07(7), 0.93(10), 0.80(10), 0.63(10), 0.43(10), 0.30(10), 0.10(10), and 0.0(2). Comparisons are made to theoretical calculations and relative bond orders. The calculated electron affinities of SF6 are: density functional, 1.6–3.0 eV; ab initio, -1.0–2.2 eV; semiempirical, 0.1–2.2 eV, and for SF5 is 0.3–3.8 eV. Curves calculated using semiempirical, density functional and ab initio procedures are similar to the anionic Morse potentials. This work attempts to correct for differences in the EA calculated for this species.

Laser based on an SF6 — H2 mixture pumped by a radially converging electron beam

Experimental and theoretical investigations were made of the excitation and emission from a high-power HF laser pumped by a nonchain chemical reaction initiated by a radially converging electron beam. The distribution of the specific radiation energy in the output beam was determined and the distribution of the input energy over the laser chamber cross section was calculated for various gas mixtures. The space-charge field influenced the input energy distribution. The output radiation energy of a mixture of the SF6 : H2=8 : 1 composition was ∼115 J at a pressure of 0.45bar when the active volume was ∼30 litres, the efficiency relative to the input energy was ∼7%—8%, and the distribution of the radiation energy over the output beam cross section was relatively uniform. For the same input energy, because of the high density of SF6, a pressure jump in SF6— H2(D2) mixtures resulting from the combined effect of the electron beam injection and the chemical reaction was several times less than in active mixtures of exciplex lasers.

High-power HF laser pumped by an electron-beam-initiated chemical nonchain reaction

The development of a high-power HF laser pumped by a chemical nonchain reaction initiated by a radially converging electron beam is reported. A radiation energy of ∼ 115 J with an efficiency of ∼ 8% in terms of deposited energy has been achieved in a mixture with an active volume of ∼ 30 liters. It is shown that because of the high SF6 density, the total pressure jump in SF6–H2(D2) mixtures caused by the electron beam injection and the chemical reactions is several times smaller than that in the active mixtures of exciplex lasers for the same input energies. This factor considerably facilitates the development of wide-aperture HF and DF lasers with an SF6 fluorine donor pumped by an electron-beam-initiated chemical nonchain reaction.

Dopant location in SF6He39,40

Recent quantum Monte Carlo studies of doped helium clusters have yielded different results for the location of the SF6 impurity, despite good agreement on helium density profiles, thus raising the question of wave function bias on structural properties. We present here a systematic analysis of the effect of the trial function on variational and diffusion Monte Carlo (VMC and DMC) results for the ground state of SF6HeN (N=39 and 40). Four different sets of wave functions are used, together with isotropic pairwise potentials. Use of a two-peak term in the He–SF6 wave function to describe the extensive helium structuring induced by the impurity greatly improves the VMC energies and helium densities. For all of the wave functions, the impurity SF6 distribution has its maximum at the cluster center in both VMC and DMC. This result agrees with the conclusion previously presented by Barnett and Whaley, but it contradicts the recent DMC result of Chin and Krotscheck. To explain this discrepancy, we analyze the amount of sampling necessary to ensure a reliable description of the SF6 density. We find that considerably more sampling is required for the impurity than for the helium density or the energy. Similar considerations are shown to affect the extent of structure seen in pure HeN density profiles.

Influence of SF6 on the Broadening and Shift of the 535.0 nm Thallium Line

Abstract The pressure broadening and shift of the 535.0 nm Tl line resulting from the photodissociation of thallium iodide mixed with sulfur hexafluoride were studied at low densities using a Fabry-Perot interferometer. A linear variation of both the width and shift of the line with the SF6 density was found and the cross sections for the broadening and shift were determined.

Simultaneous infrared transitions in N2 + SF6 and O2 + SF6 gaseous mixtures

The simultaneous transitions arising from the ν3 band of SF6 associated with the fundamental vibrations of N2 and O2 have been extensively studied. The integrated intensities, the bandwidths, and the frequency shifts of the maximal absorption have been examined as functions of the density of N2 or O2. A nonlinear effect on the integrated intensities resulting from changes in the density of SF6 was observed. The binary absorption coefficient deduced from experimental intensities has been compared with the absorption coefficient calculated by considering the theory developed by Ketelaar.

Energy removed from vibration in V-V collisions between SF6 and helium or argon

We have measured the amount of vibrational energy transferred to translation in V-V collisions between SF6 and helium or argon. We used precise mass-spectrometric measurement of the change in SF6 density in a flow of He or Ar and SF6 through a focused cw CO2 laser beam under conditions where the number of collisions in the beam was much less than the collision number for V-T deactivation. We have determined the ratio of energy lost Δ? to the number of collisions for V-V relaxation ZVV to be Z−1VVΔ? =13±6 cm−1/collision for helium and 4±2 cm−1/collision for argon. These values are independent of temperature over the range 150–300 K.

Nuclear Magnetic Relaxation and Diffusion in Liquid SF6

The longitudinal nuclear magnetic relaxation time T1 and the diffusion coefficient D in a sample of SF6 liquified under pressure have been measured by spin—echo techniques. The closed sample contained approximately a critical density of SF6. The measurements were made at temperatures between the freezing temperature, 221°K, and 315°K, which is 3.5°K below the critical temperature. Misch metal was used as an oxygen getter in the preparation of the sample. The measured values of T1 are compared with values calculated on the assumption that the relaxation is due to spin—rotational interactions and to intra- and intermolecular dipole—dipole interactions. The calculated and measured values of (1/T1) agree fairly well if reasonable values of the spin—rotational interaction constants are assumed. The calculation indicates that the nuclear magnetic relaxation of liquid SF6 is produced mainly by spin—rotational interactions.