Communication networks, and Ethernet networks in particular, have been expanded into other fields, besides the office informatics; one of their latest conquests has been industrial automation networks in substations. The recently published IEC 61850-90-4 establishes engineering lines for communication networks and systems in power utility automation. This standard proposes Ethernet with PRP and HSR protocols, defined in the IEC 62439-3, as a global standard to use in the Bus Station and Process Bus in substations. These protocols are characterized by a zero recovery time, which means that, faced with a network failure, communication is not stopped and there is no frame loss. They provide the hot-plugging feature, which allows connecting and disconnecting devices without having to stop the operation process of the network and other devices.

Their operation is based on sending duplicated frames through different paths, so that, if due to any reason one of the frames does not arrive, the other one continues being received. This increased availability has a drawback, among others, an increase of the management and processing work of the frames; in particular, a new task appears: the elimination of duplicated frames. In addition to the duplicated frames introduced by the protocols themselves, a new type of frame also appears: circulating frames, which comes up when a frame makes a complete lap in a loop of the network and arrives again over the same port to the node. The involved standards do not specify how to discard duplicates and circulating frames, but set strict time and operating conditions to be complied by the discarding method chosen.

In this thesis, these requirements are analyzed and studied, and particularly, parameters such as latency, throughput or reliability. Discard methods, which conform the requirements, are proposed in order to obtain a correct application of PRP and HSR in substations or power utility automation networks in general. The developed methods could be integrated in devices needed in this type of high availability networks. The hard conditions imposed to these protocols, so as to be used in substations, make these developments usable for other applications in which the availability parameters are as hard or more relaxed.