Globally, there is a growing trend in widely varying applications to move from existing single-purpose (and often proprietary) systems to multi-functional Ethernet networks. In this respect the power industry is no different. The IEC 61850 standard provides the framework for migrating all communications to Ethernet-based protocols.
This trend is driven by a need to move more data around the network. Much of this activity falls into the category of “Smart Grid” applications. Legacy technologies in the case of Power networks used Time-Division Multiplexing or TDM. TDM is a technology that was developed in the infancy of telecommunications. It provides the stability that is needed in such networks but is limited in its ability to transport the volume of data now sought to be carried. Packet-based networks (TCP/IP) provide the scale needed, as well as other benefits, but also present certain challenges.
The Benefits
The most obvious benefit is the continued safe operation of teleprotection systems. New Ethernet protocols such as GOOSE enable such systems to operate safely and securely. The other main benefit, as already stated, is the proliferation of data that can be gathered and moved around the network, making it more “smart”. Everything from smart meters in the home to SCADA operation and fault location alerts can be monitored enabling greater efficiency along the entire supply chain.
The Challenges
However, as already stated, adoption of Ethernet networks and the increase in volume of data presents challenges. Increased data and the nature of it demands significantly tighter timing accuracy throughout the network. IEC 61850 sets out the timing requirements needed in a modern network, with the current threshold for time error across the network set at 1µS end to end. In traditional single use networks the threshold was a much more generous 1ms!
Fig.1 shows which systems require higher accuracy.
Fig.2 the tolerances allowed to stay within the end to end budget.
The second significant challenge is that Ethernet networks provide less consistency than a traditional TDM communications link. Variations in latency, packet loss and other types of packet corruption can have serious impact particularly in distance protection schemes. Digital relays need to be resilient to a variety of network conditions. Relay manufacturers need to build resilient equipment. Utilities who use a variety of devices and protocols need to ensure proper interoperability of systems across their network.
Calnex solutions is a manufacturer of Ethernet test equipment. In later editions I will talk in more detail about the test requirements for players in the industry and specific ways in which Calnex is helping both solutions providers and the utilities themselves to test to overcome the challenges noted. If you are interested to learn more before then please feel free to ask me any questions you might have, or maybe learn more about Network Emulation uses cases here.
Peter Whitten
Product Manager