The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
In this paper, in order to study the effect of temperature gradient on long-term reliability of high voltage direct current (HVDC) cross-linked polyethylene (XLPE) cable insulation during actual operation, an aging device under DC electrical stress companied with temperature gradient(the high temperature side is 60°C and the low temperature side is 20°C) for multi-group film specimen were designed...
This paper proposes a simple method of selecting effective brain local features for age estimation from T1-weighted MR images. We also employ the high-resolution AAL atlas, which is defined by 1,024 local regions, to improve the accuracy of age estimation. We evaluate performance of the proposed method using 1,099 T1-weighted images from a large-scale brain MR image database of healthy Japanese, and...
Our previous studies showed that the aging parameter, i.e. the n-value, of XLPE was quite different from that of XLPE nanocomposites. In order to investigate the effects of space charge on aging parameter under DC voltage, the n-values of XLPE and its nanocomposites were measured under AC voltage in this report, because few space charge exits in the sample under AC voltage. Step-stress tests were...
The aging parameter n can reflect the aging property of material to some degree and determine the test voltage of the type test and prequalification test of HVDC cables. However, the aging parameter has rarely been studied systematically, especially under temperature gradient. In this paper, step-stress test was carried out to estimate the ageing parameter n of two materials, XLPE and its nanocomposites...
In recent years, HVDC cables have been greatly improved, 500kV XLPE DC cable has been developed, and many XLPE DC cables of lower applied voltage have been used in HVDC systems. However, there still is not a unified standard for testing high voltage DC extruded cable systems, only a recommendation. Furthermore the recommendation only gives a lower limit of ageing parameter (n=10 in the inverse power...
The former researches for condition assessment of oilpaper focus on the statistical results of aging factors and diagnostic data, the mechanisms of aging factors and variation law of each characteristics, which can give conclusions of aging status and furthermore, life expectations. However, the questions “How exactly can aging characteristics reflect the aging status”, “To what extent can we believe...
The hydrophobicity evaluation for polymer insulators continues to be a prominent characteristic. For the purpose of evaluating the hydrophobicity of polymer insulator, a VHF antenna was utilized to receive high frequency electromagnetic signals, which were induced during the surface discharge on the sample surface. The wavelet theory was applied to analyze the electromagnetic signals that were processed...
Because partial discharge (PD) in air-filled void embedded in the insulation system can cause the degradation and eventual insulation failure, it's necessary to study the PD mechanism. Our paper employed the equipment based on Pockels effect to investigate the change of surface charges distribution in the process of PD degradation. During PD sequences, the effect of previous discharge on subsequent...
With the assumption that the load variance of each apparatus in the reality is of the same value, the former works of Life-Cycle-Cost assessment based on actual data of accelerating degradation neglect the influence of different load to the aging process of apparatus. Nevertheless, the actual operation time can not reflect the real aging time of the insulation system. This paper assumes that in the...
Raised a new synchronization technology of ARP resource Real-time-batch synchronization technology. This technology is applied on the Ethernet switches. With the usage of this new technology, we achieved a reasonable use of system resources to ensure the consistency of the ARP resources. We use batch synchronization to reduce the utilization of CPU, and use real-time synchronization when the batch...
On the basis of statistical theory, a method to quantitatively determine the reliability of multi-parameter diagnosis and to optimize the algorithm of multi-parameter diagnosis is put forward. This method is based on the statistical law, and concerns correlation between the different parameters. Moreover, as an example, the stator bar of generator (300 MW, 18 kV) is studied. 30 samples were selected...
Light-emission of partial discharge (PD) was measured by photo multiplication tube (PMT) under AC voltage and simultaneously partial discharge magnitude was measured. Investigation of the correlation between them shows that the intensity of light emission is in proportion to PD magnitude but the ratio between them changes slightly with the aging time. Different voids were tested to study the influence...
Comparison study was carried out on the partial discharge (PD) behaviors in a void under AC voltages with square-wave and sine-wave. The transition of the PD magnitude with aging under square-wave showed the same tendency as that under sine-wave. Moreover, some distinctive characteristics of PDs under square-voltage (e.g. more than two pulses after the voltage rise time and their transition with aging)...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.