INVESTIGATION OF EXPLOSION SAFETY OF DC POLYMER SURGE ARRESTERS 3.3 KV FOR TRACTION NETWORK OF RAILWAY TRANSPORT

In the testing laboratories of Ukraine, there is no high-voltage equipment of the necessary energy for testing surge arresters for explosion safety, which does not allow to estimate this indicator at the stage of development of prototypes. In view of this test, the polymer prototypes of the DC surge arresters in polymer case (SAp) 3.3 kV were tested under the operating conditions of the equipment of the operating substation with short-circuit currents of 8.3 kA and a current time of 0.02 seconds, close to the recommended by Standard of IEC 60099-4:2014 values. 8 samples of surge arresters were tested. A sample of the surge arrester was mounted on one of the metal supports at a height of 5.5 m located in the substation and connected to the 3.3 kV traction substation buses through disconnectors and a high-speed switch. After the short-circuit breaker was closed through a column with a pre-punched or shunted copper wire varistor, a short-circuit current flowed to form an electric arc inside the arrester samples. During the tests video samples were recorded using a video recorder installed in close proximity to the test sample. The frame of the SAp samples in which the varistors were enclosed was performed either by winding the fiberglass tape on a varistor column, or from rods arranged in the form of a squirrel cage, or in the form of a fiberglass tube with a hole for gas ejection during a short circuit inside the SAp. The destruction of the hull occurred without scattering of the fragments in seven cases from the eight samples tested. In seven samples, a local rupture of the silicone shell occurred in the varistor zone, a gas ejection and an arc discharge occurred through this gap. The exception was sample No. 2, made by a continuous winding of a glass-banding tape on a varistor column, in which, during the explosion, the upper electrode exploded with the simultaneous expansion of fragments of the varistor in a radius of 3-5 m. Due to the white smoke accompanying the explosion, it was not possible to fix on the frame whether the arc output from the case to the outside, despite the fact that on the next frame (in 33 ms.) the arc was no longer fixed. In the tests of eight of the presented designs, none of them ignited the hull. If the tests were carried out on the surge arresters assembled with pre-punched varistors (electrothermal breakdown), the varistors during the tests split, remaining inside the frame. From the action of the arc in the contact zone of the aluminum electrodes with varistors, a deep burn-out of the electrodes was observed, in some cases, the burnup was up to 7 mm deep and up to 8 mm wide. If the varistors were shunted by a copper wire, they remained intact. If the varistors were shunted by a copper wire, they remained intact und melting and burning out a part of the aluminum electrodes in the area of connection with the copper wire were smaller sizes. The samples showed a completely satisfactory ability to withstand large pulse currents without dispersing dangerous fragments for personnel and surrounding equipment. However, polymer designs, the frame of which is made by continuous winding, require reinforcement of the connection zone of the carcass with electrodes to exclude the break-out of electrodes during the accumulation of gases during a short circuit inside the shell of the SAp. For such designs, an additional test for mechanical strength in the longitudinal direction with a predetermined norm is required in the acceptance test program

Long term time variability of cosmic rays and possible relevance to the development of life on Earth

An analysis is made of the manner in which the cosmic ray intensity at Earth has varied over its existence and its possible relevance to both the origin and the evolution of life. Much of the analysis relates to the 'high energy' cosmic rays ($E>10^{14}eV;=0.1PeV$) and their variability due to the changing proximity of the solar system to supernova remnants which are generally believed to be responsible for most cosmic rays up to PeV energies. It is pointed out that, on a statistical basis, there will have been considerable variations in the likely 100 My between the Earth's biosphere reaching reasonable stability and the onset of very elementary life. Interestingly, there is the increasingly strong possibility that PeV cosmic rays are responsible for the initiation of terrestrial lightning strokes and the possibility arises of considerable increases in the frequency of lightnings and thereby the formation of some of the complex molecules which are the 'building blocks of life'. Attention is also given to the well known generation of the oxides of nitrogen by lightning strokes which are poisonous to animal life but helpful to plant growth; here, too, the violent swings of cosmic ray intensities may have had relevance to evolutionary changes. A particular variant of the cosmic ray acceleration model, put forward by us, predicts an increase in lightning rate in the past and this has been sought in Korean historical records. Finally, the time dependence of the overall cosmic ray intensity, which manifests itself mainly at sub-10 GeV energies, has been examined. The relevance of cosmic rays to the 'global electrical circuit' points to the importance of this concept.Comment: 18 pages, 5 figures, accepted by 'Surveys in Geophysics

Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP

Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events. Decay-plane correlations, consistent with zero and with the Standard Model predictions, are measured

Ultrarelativistic sources in nonlinear electrodynamics

The fields of rapidly moving sources are studied within nonlinear electrodynamics by boosting the fields of sources at rest. As a consequence of the ultrarelativistic limit the delta-like electromagnetic shock waves are found. The character of the field within the shock depends on the theory of nonlinear electrodynamics considered. In particular, we obtain the field of an ultrarelativistic charge in the Born-Infeld theory.Comment: 10 pages, 3 figure

Measurement of the Cross Section for Open-Beauty Production in Photon-Photon Collisions at LEP

The cross section for open-beauty production in photon-photon collisions is measured using the whole high-energy and high-luminosity data sample collected by the L3 detector at LEP. This corresponds to 627/pb of integrated luminosity for electron-positron centre-of-mass energies from 189GeV to 209GeV. Events containing b quarks are identified through their semi-leptonic decay into electrons or muons. The e+e- -> e+e-b b~X cross section is measured within our fiducial volume and then extrapolated to the full phase space. These results are found to be in significant excess with respect to Monte Carlo predictions and next-to-leading order QCD calculations

Measurement of W Polarisation at LEP

The three different helicity states of W bosons produced in the reaction e+ e- -> W+ W- -> l nu q q~ at LEP are studied using leptonic and hadronic W decays. Data at centre-of-mass energies \sqrt s = 183-209 GeV are used to measure the polarisation of W bosons, and its dependence on the W boson production angle. The fraction of longitudinally polarised W bosons is measured to be 0.218 \pm 0.027 \pm 0.016 where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model expectation

Measurement of the Atmospheric Muon Spectrum from 20 to 3000 GeV

The absolute muon flux between 20 GeV and 3000 GeV is measured with the L3 magnetic muon spectrometer for zenith angles ranging from 0 degree to 58 degree. Due to the large exposure of about 150 m2 sr d, and the excellent momentum resolution of the L3 muon chambers, a precision of 2.3 % at 150 GeV in the vertical direction is achieved. The ratio of positive to negative muons is studied between 20 GeV and 500 GeV, and the average vertical muon charge ratio is found to be 1.285 +- 0.003 (stat.) +- 0.019 (syst.).Comment: Total 32 pages, 9Figure

Search for Branons at LEP

We search, in the context of extra-dimension scenarios, for the possible existence of brane fluctuations, called branons. Events with a single photon or a single Z-boson and missing energy and momentum collected with the L3 detector in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are analysed. No excess over the Standard Model expectations is found and a lower limit at 95% confidence level of 103 GeV is derived for the mass of branons, for a scenario with small brane tensions. Alternatively, under the assumption of a light branon, brane tensions below 180 GeV are excluded

Neutral-Current Four-Fermion Production in e+e- Interactions at LEP

Neutral-current four-fermion production, e+e- -> ffff is studied in 0.7/fb of data collected with the L3 detector at LEP at centre-of-mass energies root(s)=183-209GeV. Four final states are considered: qqvv, qqll, llll and llvv, where l denotes either an electron or a muon. Their cross sections are measured and found to agree with the Standard Model predictions. In addition, the e+e- -> Zgamma* -> ffff process is studied and its total cross section at the average centre-of-mass energy 196.6GeV is found to be 0.29 +/- 0.05 +/- 0.03 pb, where the first uncertainty is statistical and the second systematic, in agreement with the Standard Model prediction of 0.22 pb. Finally, the mass spectra of the qqll final states are analysed to search for the possible production of a new neutral heavy particle, for which no evidence is found

Measurement of Exclusive rho+rho- Production in Mid-Virtuality Two-Photon Interactions and Study of the gamma gamma* -> rho rho Process at LEP

Exclusive rho+rho- production in two-photon collisions between a quasi-real photon, gamma, and a mid-virtuality photon, gamma*, is studied with data collected at LEP at centre-of-mass energies root(s)=183-209GeV with a total integrated luminosity of 684.8pb^-1. The cross section of the gamma gamma* -> rho+ rho- process is determined as a function of the photon virtuality, Q^2, and the two-photon centre-of-mass energy, W_gg, in the kinematic region: 0.2GeV^2 < Q^2 <0.85GeV^2 and 1.1GeV < W_gg < 3GeV. These results, together with previous L3 measurements of rho0 rho0 and rho+ rho- production, allow a study of the gamma gamma* -> rho rho process over the Q^2-region 0.2GeV^2 < Q^2 < 30 GeV^2