Showing papers on "Partial discharge published in 1970"
TL;DR: In this article, a study of the partial discharge characteristics of polyethylene cavities under combined 60-Hz and negative 1.2/50-s impulse stresses, the amplitude of the altemating stress being below discharge inception value, was made.
Abstract: A study has been made of the partial discharge characteristics of artificial cavities in polyethylene under combined 60-Hz and negative 1.2/50-?s impulse stresses, the amplitude of the altemating stress being below discharge inception value. Samples of cross-linked and low-density polyethylenes were tested. The discharge sequence was derived from the results of previous tests, which used only impulse stresses. It showed that the ac discharges, initiated by an impulse, could continue indefinitely under certain conditions. The experimental results do not confirm this but show that the ac discharges always extinguish within 10 seconds after the application of the impulse. The number of ac discharges, although independent of the amplitude of the impulse, increases with increasing altemating stress but decreases as the sample ages. The effect of the angle of the cycle at which the impulse was applied on the combined discharge inception stress is also described.
20 citations
01 Jan 1970
TL;DR: In this article, the validity of frequency-accelerated discharge tests for sold insulation when discharge measurements, dielectric deterioration and sample life are related to the service 50Hz conditions was considered.
Abstract: The paper considers the validity of frequency-accelerated discharge tests for sold insulation when discharge measurements, dielectric deterioration and sample life are related to the service 50Hz conditions. The work includes details of a high-resolution discharge detector developed for use over the frequency range 50–1250Hz. Experiments on low-loss organic materials, e.g. polythene, showed that, under certain experimental and environmental conditions, fundamental changes in the discharge-pulse-amplitude distribution occurred with changes in the test frequency. These were related to the manner in which the dielectric surface discharged as a number of single events over each voltage cycle. There was no change in the mechanism of failure over the frequency range 50–1250Hz, and ‘lifetime ∞ 1/frequency’ was a reasonable approximation. Trends in the progression of discharge measurements were not dependent on the test frequency. The greatest change in the discharge-pulse-amplitude distribution with test frequency occurred in circulating air at relatively high flow rates. This environment gave the most consistent result in terms of sample lifetime in cycles of applied voltage.
9 citations
Patent•
10 Sep 1970
TL;DR: In this paper, a system for automatically controlling flash illumination of a camera so as to achieve a proper exposure was proposed, where the flash tube of the camera is energized from a capacitor which initially has a predetermined charge.
Abstract: A system for automatically controlling flash illumination of a camera so as to achieve a proper exposure. The flash tube of the camera is energized from a capacitor which initially has a predetermined charge. Prior to energizing of the camera flash with this capacitor, a discharge circuit is connected to the capacitor for preliminarily discharging the capacitor to an extent determined by the photographing conditions. After this initial discharge, the charge remaining at the capacitor will also correspond to the photographing conditions, and it is this remaining charge which is then used for energizing the flash tube in connection with exposure of film in the camera.
9 citations
Patent•
21 Jan 1970
TL;DR: In this article, an electrical glow discharge detector for detecting small amounts of gaseous impurity in a gas, having a pair of electrodes in a fluid-tight chamber provided with a constant bore capillary tube inlet, was presented.
Abstract: The invention relates to an electrical glow discharge detector for detecting small amounts of gaseous impurity in a gas, having a pair of electrodes in a fluid-tight chamber provided with a constant bore capillary tube inlet. The sensitivity of the detector is improved by applying across the electrodes a power source capable of both supplying a low, sensitive, discharge voltage and a high discharge starting voltage to restart the discharge if the sensitive voltage should permit it to fail.
6 citations
Patent•
08 May 1970
TL;DR: In this paper, the authors proposed a circuit for initiating discharge of gaseous discharge devices having a trigger electrode, where a high-voltage trigger pulse between a trigger and a main electrode of the discharge device and simultaneously to add a highvoltage pulse derived from the trigger pulse in series with the voltage on the main discharge capacitor were applied.
Abstract: This invention relates to circuits for initiating discharge of gaseous discharge devices having a trigger electrode. These circuits are arranged to apply a high-voltage trigger pulse between a trigger electrode and a main electrode of the discharge device and simultaneously to add a high-voltage pulse derived from the trigger pulse in series with the voltage on the main discharge capacitor to accelerate breakdown between the main electrodes of the discharge device.
4 citations
01 Jul 1970
2 citations
TL;DR: Experimental studies were conducted on lapped high-density polyethylene tape dielectric pressurized mainly with SF6 to clarify its performance under conditions of overvoltage in EHV systems as discussed by the authors.
Abstract: Experimental studies were conducted on lapped high-density polyethylene tape dielectric pressurized mainly with SF6 to clarify its performance under conditions of overvoltage in EHV systems.
1 citations
01 Jan 1970
1 citations
Patent•
23 Dec 1970
TL;DR: A quick make, quick break circuit for an electromagnetic relay having two oppositely wound coils 2, 3 on the same core as discussed by the authors, has one coil 2 in a circuit branch with a switch 7 and the other coil 3 in an opposite wire with a capacitor 8; the two circuit branches being in parallel and connected to a DC source 6 through a resistor.
Abstract: 1,216,686 Electromagnetic relays STANDARD TELEPHONES & CABLES Ltd 18 July, 1968, No 34168/68 Heading H1N A quick make, quick break circuit for an electromagnetic device such as a relay having two oppositely wound coils 2, 3 on the same core 1, has one coil 2 in a circuit branch with a switch 7 and the other coil 3 in a circuit branch with a capacitor 8; the two circuit branches being in parallel and connected to a DC source 6 through a resistor 5 When the switch 7 is closed the coil 2 is energized from the source 6 and due to the voltage drop at 4 the capacitor 8 will partly discharge through coils 3, 2 which will assist each other to operate the relay The holding current will be the steady state current in coil 2 after partial discharge of capacitor 8 When the switch 7 is opened the current in coil 2 ceases and opposite magnetization is produced in coil 3 as the capacitor 8 charges to the source voltage
1 citations