Natural Aging of Non-Energized Aluminum Conductors
This paper reports the results of a photographic and electrical study of the mechanism by which a new aluminum conductor ages. A systematic approach of monitoring the aging process revealed the movement of water drop location from the top of a new conductor to the bottom of an aged conductor. Through photographic water drop analysis and electrical test results it has been determined that an aluminum conductor, even though not energized, is essentially aged in 4 to 7 months in the environment of northern Indiana, USA. A seasonal effect was found to add up to 5 months to this period.
The effect of surface roughness on corona-generated electromagnetic interference for long-term operating conductors
This paper presents a research of the surface roughness effects on corona-generated electromagnetic interference of long-term operating conductors. The detailed surface morphologies and roughness of typical long-term operating conductors were measured and analyzed. The radio noise measurement system based on the corona cage was discussed and the actual radio noise generated by the conductor in the measured cage was obtained, based on the parameters of the corona cage and the measured data. The radio noise tests were carried out under both dry and wet conditions. Under two types of conditions, the corona intensity was higher on the long-term operating conductors contrasted to the new conductors as a result of the anomalistic surfaces of the long-term operating conductors. The rate of decrease of corona inception voltages between the long-term operating conductors and new conductors was discovered to increase with the raise of surface roughness degree Ra in linear relationship. Approximate linear relation was also discovered between the averaged radio noise deviation and Ra. The rate of decrease of corona inception voltages under wet conditions was slightly higher (about 1%) than that under dry conditions. The difference between the radio noise of long-term operating conductors and that of new conductors was larger (1.3 dB) under wet conditions compared to dry conditions.
Substation automation based on IEC 61850 with new process-close technologies
New technologies in primary equipment like nonconventional instrument transformers require new interfaces to the substation automation system. The future standard IEC 61850 perfectly supports this requirement. With the introduction of the new technologies and the use of IEC 61850, a more decentralized architecture of the substation automation system will be possible. This provides several benefits but a careful system design is required to maintain the overall reliability of the system.