Applying radio communication in distribution generation teleprotection schemes

The value of teleprotection schemes at the transmission level has been well established. Varieties of channels have been employed as communications technologies advanced. The associated schemes have been tailored to both the function served and the available channel characteristics. The use of communication at the distribution level was considered unnecessary until recently because conventional distribution networks have been comprised of radial feeders without generation sources, where time-coordinated overcurrent schemes have provided adequate protection. The advent of distributed generation (DG) introduces several new challenges. A high penetration of DG can result in a loss of sensitivity and/or coordination of the existing feeder ground fault protection. Another concern is effective islanding protection. Passive anti-islanding schemes can fail if the generation output approaches the level of load within the island. Direct transfer tripping schemes solve this challenge but are typically complex if there are multiple upstream devices that can open to form an island or if the DG can be transferred among feeders. Conventional communications channels usually prove to be cost-prohibitive for applications at the distribution level. However, new technologies for wireless communication have become available recently, which are much more cost-effective but have characteristics that can differ from more traditional channels. This paper illustrates how teleprotection schemes can be designed to suit both the new challenges in distribution networks and the characteristics of the wireless channel. These schemes provide reliable and cost-effective solutions, allowing DG to be integrated without compromising the operation of the distribution network.