With the increase in the voltage and capacitance of gas‐insulated transmission lines (GILs), the insulation failure of GIL has attracted more and more attention. Further understanding of the partial discharge (PD) and flashover characteristics of metal particles on the insulator surface, as well as the flashover mechanism, is necessary to reduce the failure rate and improve the reliability of the equipment. In this study, an ultra‐high voltage (UHV) AC insulator PD test and measurement system based on the cross‐reference pulse current (PC) and ultra‐high frequency (UHF) methods were established. The PD development and flashover characteristics of 5 mm‐long metal particles at different positions on the surface of a UHV AC insulator, as well as the surface charge accumulation, were studied. The results show that the discharge of millimetre‐scale metal particles on the insulator surface under PD test conditions is relatively low (generally lower than 2PC), and it is difficult to be detected by the conventional PC and UHF methods due to their insufficient sensitivity. Moreover, it is found that the weak PDs of the millimetre‐scale metal particles will result in a charge accumulation on the insulator surface under AC voltage, which eventually will lead to the insulator flashover. The PDs of the UHV AC insulator before flashover are generally small, which will make it difficult for online monitoring systems to give an effective alarm before flashover.

Metal particles and dirty contaminants on the spacer surface are mainly considered to be the critical factor in sudden flashovers. Understanding the discharge characteristics as well as the detectability of metal particles in the gas-insulated switchgear (GIS) will be helpful in improving its safety and reliability. In this paper, a high-sensitivity measurement system based on cross-reference pulse current (PC) and ultra-high-frequency (UHF) methods was established. The PC and UHF signals generated by partial discharges (PDs) of metal particles of different lengths (Φ = 0.5 mm, L = 2, 5, 8, and 10 mm) at different positions on a real spacer surface were studied. The PD characteristics and detectability of the metal particles on the spacer surface were obtained while the detection limitation was also discussed. It is found that under PD test condition, the apparent charge of the PDs is less than 1 pC for particles shorter than 5 mm, and the conventional PD detection method have limitations in detecting these short particles on the spacer surface. Under operation condition, only the apparent charge of particles longer than 8 mm can exceed 1 pC, which means it is difficult to detect the particles shorter than 8 mm in field. However, the result indicates that even the 5 mm long particle will be harmful to the GIS. Meanwhile, it is also been found that the detection sensitivity also has a great influence on the judgement of PD severity. This study is of great interest for understanding the PD characteristics, discharge levels, and detectability of short metal particles on spacer surface.

The current Internet addressing architecture does not verify the source address of a packet received and forwarded. This causes serious security and accounting problems. Based on the drastically increased IPv6 address space, a "source address validation architecture" (SAVA) is proposed in this paper, which can guarantee that every packet received and forwarded holds an authenticated source IP address. The design goals of the architecture are lightweight, loose coupling, "multi-fence support" and incremental deployment. This paper discusses the details of design and implementation for the architecture, including inter-AS, intra-AS and local subnet. This architecture is deployed into the CNGI-CERNET2 infrastructure -a large-scale native IPv6 backbone network of the China Next Generation Internet project. We believe that the source address validation architecture will help the transition to a new, more secure and sustainable Internet.

This document presents the China Education and Research Network (CERNET)'s IVI translation design and deployment

This note describes a framework for IPv4/IPv6 translation. This is in the context of replacing Network Address Translation-Protocol Translation (NAT-PT), which was deprecated by RFC 4966, and to enable networks to have IPv4 and IPv6 coexist in a somewhat rational manner while transitioning to an IPv6 network.

Gas insulated switchgear (GIS) insulation failures occur frequently in field operations, seriously affecting the reliability of power systems. Fault statistics show that nearly half of the insulation flashover faults in field operation are strongly related to the switching operation, and metal particles are considered to be a crucial cause of flashover. The impact vibration generated by the switching operation may activate the metal particles and make them lift and jump in the GIS, reducing the insulation performance. Therefore, in this study, an experimental platform was established to simulate the impact vibration generated by the switching operation. The flashover characteristics induced by metal particles under impact vibration were studied, and the movement behavior of metal particles was also analyzed. The results show that metal particles lying on the enclosure lift under the impact vibration and then keep jumping in the GIS. These particles can jump to cause insulator flashover with high probability after the impact vibration. The longer the metal particles, the higher the probability of insulator flashover, and the shorter the average jump duration of the metal particles before the flashover. Moreover, compared with the flake particles, linear particles are more likely to cause insulator flashover after the impact vibration. This study demonstrates the mechanism of insulator flashover caused by metal particles under impact vibration, which provides a significant support for understanding the insulation failures strongly related to the switching operation in practical applications.