A study of photolysis of polychlorobiphenyl-containing transformer oil by UV spectroscopy

UV absorption spectra of polychlorobiphenyls in transformer oil have been studied. We have shown that the absorption of the corresponding bands decreases with the growth of the time of irradiation. At t = 40 min, the degree of transformation of Abs is up to 40–66%.     

A study of the precipitation mechanism in GK transformer oil

The room-temperature IR spectra of fresh, used, and aged under model conditions GK trans-former oil, as well as of its residue, are recorded, interpreted, and compared. Analysis of the data obtained confirms the presence of small amounts of aromatic compounds in these samples and shows that the fraction of aromatic and oxidized compounds in transformer oil increases during exploitation. Based on this, a new precipitation mechanism in transformer oil is proposed.     

On light scattering in transformer oil

GK transformer oil is studied using the methods of UV and visible spectroscopy, dynamic light scattering, small-angle light scattering, scanning electron microscopy, and element analysis. The effect exerted on the optical properties of transformer oil by colloidal, micelle-like, and solid particles formed in oil during its exploitation is investigated.     

Self-focusing in transformer oil with external electric field

We report a pioneer observation of self-focusing in transformer oil with external electric field. The experiments were conducted at variable powers (5?C15 mW) of red He-Ne laser at various adjustable external electric field intensities (0?C15 kV/cm). Self-defocusing in transformer oil is observed in the absence of electric field. While with the applied electric field, self-focusing is witnessed that became excessively strong at high electric field. It is further observed that beam divergence decreases with the increase of electric field and it reduces by about 70% at 15 kV/cm. Self-focusing has been observed with both polarized and unpolarized laser light.     

Determination of the hydrogen diffusion coefficient in transformer oil

The hydrogen diffusion coefficient in transformer oil is determined by optically monitoring the dynamics of the hydrogen bubble dissolution in pure degassed oil. The diffusion coefficient is found to be roughly two orders of magnitude smaller than those determined earlier. This result is of great importance for chromatographic analysis of gases dissolved in transformer oil, since it gives grounds to suspect that hydrogen is not so volatile as implicitly believed in a number of works. Accordingly, the reliability of diagnostic data for high-voltage oil-filled equipment improves.     

高功率超宽带变压器油透镜天线设计与仿真

将TEM喇叭天线密封进填充变压器油的尼龙天线罩中,只要合理设计尼龙天线罩外形,使变压器油形成聚焦透镜,不仅能提高天线的功率容量,还能改善其辐射特性。基于变压器油的缩波效应和椭球的几何性质,借助几何光学理论,设计了一款具有聚焦能力的椭球变压器油透镜。变压器油的缩波效应能够增大TEM喇叭天线电尺寸,使TEM喇叭天线的辐射特性得到初步改善,透镜的聚焦能力使天线的定向性得到进一步改善。为了验证理论分析的正确性,另外设计了一款不具有聚焦能力的球状变压器油透镜作为参照,两款透镜天线仿真结果与理论分析吻合。与大气中的TEM喇叭天线相比,椭球变压器油透镜使TEM喇叭天线主波束变窄,远场电压峰峰值提高56.97%,阻抗带宽低频端从0.28GHz扩展到0.2GHz,功率容量达到18.43GW。     

高功率超宽带变压器油透镜天线设计与仿真

将TEM喇叭天线密封进填充变压器油的尼龙天线罩中,只要合理设计尼龙天线罩外形,使变压器油形成聚焦透镜,不仅能提高天线的功率容量,还能改善其辐射特性。基于变压器油的缩波效应和椭球的几何性质,借助几何光学理论,设计了一款具有聚焦能力的椭球变压器油透镜。变压器油的缩波效应能够增大TEM喇叭天线电尺寸,使TEM喇叭天线的辐射特性得到初步改善,透镜的聚焦能力使天线的定向性得到进一步改善。为了验证理论分析的正确性,另外设计了一款不具有聚焦能力的球状变压器油透镜作为参照,两款透镜天线仿真结果与理论分析吻合。与大气中的TEM喇叭天线相比,椭球变压器油透镜使TEM喇叭天线主波束变窄,远场电压峰峰值提高56.97%,阻抗带宽低频端从0.28 GHz扩展到0.2 GHz,功率容量达到18.43 GW。     

Laser interferometric study of the physical properties of transformer oil

This paper describes the optical, thermal, and electrical properties of an important nonpolar dielectric liquid, transformer oil. Applying dual laser (He–Ne and Argon laser of wavelengths 632.8 and 514.5 nm, respectively), and the Mach–Zehnder interferometric technique, the refractive indices and its temperature gradients are determined. Using Maxwell's and Cauchy's equations, the following optical, thermal, and electrical properties are calculated: optical and dielectric dispersion, optical permittivity and its thermal coefficient, thermal coefficient of volume expansion, specific refraction, specific dispersivity, characteristic impedance, electric susceptibility, and the variation of Cauchy's emperical constants with temperature. Additionally, different physical phenomena are studied as functions of wavelength and temperature.     

重频纳秒高压脉冲下变压器油击穿特性的实验研究

介绍了重频纳秒高压脉冲下变压器油绝缘特性研究的现状和成果。进行了重频（1 Hz～1 kHz）纳秒高压脉冲下25#变压器油击穿特性的实验研究。实验发现相对于单次纳秒脉冲,重频脉冲下25#变压器油的击穿场强与频率相关,频率提高,击穿场强降低,但不是线性关系,在频率超过100 Hz时变压器油的击穿场强变化较小,在10~100 Hz时变压器油的击穿场强迅速下降。初步总结了重复频率、脉冲宽度和击穿场强的关系,对重频脉冲下变压器油的击穿机理进行了初步的探讨。     

重频纳秒高压脉冲下变压器油击穿特性的实验研究

介绍了重频纳秒高压脉冲下变压器油绝缘特性研究的现状和成果。进行了重频（1 Hz～1 kHz）纳秒高压脉冲下25#变压器油击穿特性的实验研究。实验发现相对于单次纳秒脉冲,重频脉冲下25#变压器油的击穿场强与频率相关,频率提高,击穿场强降低,但不是线性关系,在频率超过100 Hz时变压器油的击穿场强变化较小,在10~100 Hz时变压器油的击穿场强迅速下降。初步总结了重复频率、脉冲宽度和击穿场强的关系,对重频脉冲下变压器油的击穿机理进行了初步的探讨。     

高压重复频率快脉冲下变压器油中的闪络

介绍了重复频率快脉冲下固/液体介质交接面闪络初步的实验结果.脉冲功率源为基于半导体断路开关(SOS)的SPG200,固体介质为有机玻璃和尼龙,液体介质为变压器油.在相对低频阶段,闪络耐压时间与闪络场强随外加电压脉冲频率的增加非线性迅速减小,在约200 Hz以后,两者下降的趋势明显减缓.随着脉冲频率的增加,闪络耐压时间在统计上变小的同时,在一定区间内的分布也更均匀.分析表明,在不同实验条件下,重复频率显著低于单次下的沿面闪络和体击穿场强.两类场强都随脉冲频率增加非线性下降,在约200 Hz以后,下降的程度减弱.闪络场强随重复频率电压脉冲频率的变化表明,电压作用时间是绝缘介质击穿的根本要素,脉冲电压对绝缘介质的作用时间越长,沿面闪络越容易发生.     

纳秒脉冲下变压器油中闪络光信号特性

对变压器油中闪络过程的光信号特性进行了分析。在预闪络阶段,光信号呈现出脉宽为2~4 ns,幅值为30~50 mV的不规则脉冲;临近闪络阶段,光信号频率更高,脉宽为1/2~1/3 ns,最高幅值也增长到约70 mV;在闪络阶段,光信号波形呈现出1个波峰或者2个波峰的形状,幅值差异显著。光信号的形状预示了闪络中流注通道的发展过程及流注通道中粒子的变化。分析表明：光电离是纳秒脉冲下变压器油中闪络的重要因素。     

纳秒脉冲下变压器油中闪络光信号特性

 对变压器油中闪络过程的光信号特性进行了分析。在预闪络阶段,光信号呈现出脉宽为2~4 ns,幅值为30~50 mV的不规则脉冲;临近闪络阶段,光信号频率更高,脉宽为1/2~1/3 ns,最高幅值也增长到约70 mV;在闪络阶段,光信号波形呈现出1个波峰或者2个波峰的形状,幅值差异显著。光信号的形状预示了闪络中流注通道的发展过程及流注通道中粒子的变化。分析表明：光电离是纳秒脉冲下变压器油中闪络的重要因素。     

UV cavity enhanced absorption spectroscopy of the hydroxyl radical

We present the application of a continuous-wave ultra-violet tuneable light source for detection of the hydroxyl radical (OH) using cavity-enhanced absorption spectroscopy of the Q₁₁(2) and Q₂₁(2) absorption lines in the A²⁺(v=0)²_3/2(v=0) band at ca. 308 nm. A tuneable infra-red diode laser operating at 835 nm and either an Ar⁺ laser or a single frequency continuous-wave intracavity frequency-doubled diode laser, both operating at ca. 488 nm, were used to produce 0.1–0.5 W of tuneable radiation at ca. 308 nm by sum frequency generation in a BaB₂O₄ crystal. Cavity enhanced absorption spectroscopy was used to detect OH generated by UV photolysis of water vapour in argon, nitrogen, neon and helium at atmospheric pressure. A noise-equivalent (1) absorption sensitivity of 2.1×10^-7 cm^-1Hz^-1/2 measured over 128 scans in a time of 1.16 s was demonstrated with mirrors of reflectivity 0.9963 in a cavity of length 58.5 cm for a 2 cm^-1 scanning range at a UV power of 0.5 W. An OH detection limit (1) of 3.84×10⁹ moleculecm^-3 was estimated in argon at atmospheric pressure. OH collisional broadening in humidified N₂, Ar, Ne and He was determined at atmospheric pressure . PACS 39.30.+w; 42.55.Px; 42.62.Fi; 42.68.Ca     

Low-temperature time-resolved vacuum UV spectroscopy of potassium pentaborate crystals

For the first time, subnanosecond time resolution is attained in the low-temperature (at 7 K) measurements of the photoluminescence (PL) spectra (2–6 eV), the PL excitation spectra (4–32 eV), the PL kinetics, and the reflection spectra (4–21 eV) of undoped potassium pentaborate KB₅O₈·4H₂O (KB5) crystals under selective photoexcitation by synchrotron radiation. The PL peaks associated with the intrinsic defects of the KB5 lattice are detected. The PL bands resulting from radiative annihilation of the localized and self-localized electron excitations are singled out; these excitations are most efficiently photogenerated at the fundamental absorption edge in the region where the free exciton formation is expected. The difference between the PL spectra of the fast and slow components is revealed. An effective low-temperature energy transport over the KB5 hydrogen sublattice is deduced from a drop in efficiency of PL excitation in the interband-transition region as a result of nonradiative energy loss. Long-term vacuum UV irradiation of a KB5 crystal at 7 K gives rise to defects in the hydrogen sublattice, which facilitate localization of the electron excitations and reduce the effective length of their diffusion. This leads to a decrease in the nonradiative energy loss, thus enhancing the efficiency of the PL photoexcitation in the band-to-band transition region.     

Impact of various stresses on the streaming electrification of transformer oil

In this contribution the influence of various stresses and their combined impact on the electrostatic charging tendency of oil is studied. Various physicochemical properties were measured according to ASTM Standards to detect changes in oil quality. A free radical reagent, 2.2 diphenyl-1-picrylhydrazyl (DPPH), was added to oil before and after the application of stresses to determine free radical concentration. The results obtained show that the application of stresses contributes to an increase in the electrification current. These results also demonstrate that electrification current is affected by the quantity of the free radicals.     

纳秒脉冲下变压器油两相流注放电仿真研究

为揭示液体电介质击穿过程中形成的气体放电通道对液体电介质放电过程的影响,以针—板电极间隙变压器油为研究对象,基于等离子体流体力学模型,引入了液体电介质放电过程中气相放电通道对电离机制及自由电荷迁移率的影响,建立了用于模拟脉冲电压下液体电介质放电过程的两相流体模型,仿真研究了纳秒脉冲下针板电极流注放电的起始与发展过程。仿真结果表明：采用Heaviside方程可以在模型的不同区域同时实现气相物理过程和液相物理过程的模拟与计算。气相物理过程的引入导致流注尾部电场显著降低,流注头部电场进一步增强,使流注通道的发展速度要高于传统液相模型,有助于加深对纳秒脉冲下液体电介质中预击穿流注的起始、发展过程的认识和理解。     

Identification of waste cooking oil and vegetable oil via Raman spectroscopy

This paper made a qualitative identification of ordinary vegetable oil and waste cooking oil based on Raman spectroscopy. Raman spectra of 73 samples of four varieties oil were acquired through the portable Raman spectrometer. Then, a partial least squares discriminant analysis (PLS‐DA) model and a discrimination model based on characteristic wave band ratio were established. A classification variable model of olive oil, peanut oil, corn oil and waste cooking oil that was established through the PLS‐DA model could identify waste cooking oil accurately from vegetable oils. The identification model established based on selection of waveband characteristics and intensity ratio of different Raman spectrum characteristic peaks could distinguish vegetable oils from waste cooking oil accurately. Research results demonstrated that both ratio method and PLS‐DA could identify waste cooking oil samples accurately. The identification model based on characteristic waveband ratio is simpler than PLS‐DA model. It is widely applicable to identification of waste cooking oil. Copyright © 2016 John Wiley & Sons, Ltd.