Period Of Current Flow Research Articles

Research on Partial Discharge Characteristics of Suspension Defect in GIS under the Action of Voltage and Current

Abstract Gas insulated switchgear (GIS) is a critical component in power system, and the insulation testing is crucial before putting it into operation. Despite passing AC withstand tests, some GIS equipment exhibit insulation faults during operation. Existing AC withstand tests fall short in detecting all insulation faults in GIS equipment. To address this issue, a proposal is made to conduct a comprehensive simulation of actual GIS equipment operating conditions through a combined voltage and current boost test, aiming to address the limitations of existing tests. This study, based on a 330kV GIS test platform, compares the partial discharge characteristics of suspension defects under traditional voltage-boosting mode and the combined voltage and current boost mode. The research investigates the influence of simultaneously applying voltage and current on discharge characteristics. It is observed that the voltage and current boost combined mode significantly increase the partial discharge inception voltage (PDIV) and the corresponding apparent discharge compared to other modes. The apparent discharge quantity after a certain period of current flow during the discharge development process is greater than that observed in other modes. The current notably enhances the ultrasonic amplitude of partial discharge. These findings establish an experimental foundation for conducting voltage and current combined boost tests in the field.

An electrical circuit model of chemoreceptor cells based on adaptation and disadaptation time constants: implications for temporal filtering

Chemoreceptor cells have temporally dynamic physiological properties that serve as filters for fluctuating odor patterns. A computational model, based on an electrical circuit, of a peripheral chemoreceptor cell was developed based on two time constants (τ1 and τ2) that model sensory adaptation and recovery from adaptation. With τ1 set to 0.1 s and τ2 to 3.8 s, our model receptor cell responded like real olfactory cells when presented with a series of odor pulse trains. As in real olfactory cells, changes in response magnitude and frequency filtering were observed with changes in stimulation frequency. When presented with chaotic stimulus patterns, model receptor cells responded with brief periods of current flow and adapted quickly. Decreases in the first time constant (τ1) decreased the response magnitude, while decreases in the second time constant (τ2) increased the response magnitude and pulse frequency resolution during chaotic odor stimulation. The two time constants are important for determining different filter properties of the chemoreceptor cells and define the temporal range of chemical fluctuations to which a single cell will respond.

Millimetre-wave diagnostics of a pinched linear discharge

Experiments were carried out using 8.9 and 4.3 mm radiation to explore the properties of a pinched discharge between plane electrodes. The discharge had a maximum energy of 10kJ at 10kV and took place in argon at pressures of 75 and 300μm Hg. Millimetre-wave radiation was directed on to the discharge tube normal to its axis, and the transmitted and reflected signals were recorded. Analysis of these records gave detailed information about the times of certain changes in the plasma, not only during the afterglow but also during the much shorter period of current flow when pinching, if any, occurred. Observations were, in general, found to be independent of the shape of the incident beam, but were critically dependent on the gas pressure and therefore on the flow rate and the discharge-repetition frequency. Other measurements-of voltage, current and luminosity-were used as required to augment and compare with the millimetre-wave results: where comparison could be made, the agreement was good.

Effect of cortical polarization on a conditioned avoidance response

A conditioned forelimb flexion response was established in twelve rabbits using a flickering light as the conditional signal and an electric shock to the limb as the unconditional stimulus. Transcortical potential gradients (current density, 10 μa per mm 2) were imposed upon the visual receiving area, or upon the relevant portion of motor cortex bilaterally. Surface cathodal polarization of visual cortex produced a striking decrement in performance of the conditioned avoidance response in trials carried out during the period of current flow, and also on the subsequent day of training. No definite change in performance was seen during surface cathodal polarization of motor cortex, or during passage of surface anodal current through either motor or visual cortex. There was suggestive evidence of an improvement in performance on the day following application of surface anodal current to the visual cortex.

The emission of light from spark discharges.

The investigation is concerned with the transitory effects occurring in spark channels, after the discharge gap has been' bridged completely by a streamer. Observations have been made for various gases, in particular for hydrogen and argon, at pressures of the order of 1 atm. The main features studied are the light emitted from the spark channel during the period of current flow, and also the after-glow which persists after the current has fallen to a negligible value. The results indicate that the after-glow in hydrogen is probably a thermal effect only, whilst in argon it is due also, indeed largely, to other causes of which the persistence of atoms in metastable states is the most likely. Two main experimental methods were employed: ( a ) a revolving mirror camera, similar in principle to those used previously by several investigators, and ( b ) a photoelectric electron multiplier tube coupled directly to a cathode ray oscillograph. The latter method, which is new in investigations of this character, enables quantitative light emission results to be obtained, and methods of calibrating the apparatus are described in detail. The overall time constant of the circuit was sufficiently small to enable after-glows of duration as low as 1 μsec. to be clearly distinguished. The measurements show that for currents of about 100 amp., lasting for 2-4/isec., the after-glow in argon at a pressure of about 1 atm. could be detected after some 30 μsec., whereas in hydrogen, for similar conditions, the after-glow lasted for only some 3 μsec. Other gases showed after-glows of durations varying between the limits set by hydrogen and argon. In order to correlate the light output with energy dissipation in the spark channel, calorimetric measurements were made from which the mean voltage drop during the passage of current was estimated. The channel radii were measured with photographic plates sensitive to the visible and near ultraviolet light. Observations were also made of the spectra of the light emitted from the channel. The argon spectrum showed a strong continuum, and, for hydrogen, only the Balmer lines, much broadened, were seen. The density of ionization in the spark channels is deduced approximately in several ways, from the Stark effect, in hydrogen, and from a consideration of the energy balance in the channel, in both hydrogen and argon. The various calculations are in fairly close agreement and give N i ~10 17 ions per c.c. Channel temperatures, as determined on the basis of Saha’s equation, the limited applicability of which is discussed, are shown to be about 10,000- 15,000° K. The mechanism of light emission from the channel is discussed in some detail, and it is shown that either normal excitation or electron-ion recombination could be entirely responsible for the observed effects.