Synchronizing clocks is an important and difficult problem in any computer network. When the network is used to supervise, control and collect data from IEDs in a substation environment, clocks need to be synchronized to an offset of less than one millisecond.
A well-known, widespread protocol for clock synchronization is NTP, the Network Time Protocol. NTP has a hierarchical design for clock synchronization. GPS-controlled Network Time Servers (NTSs) are at the top of the synchronization "tree". These are called Stratum 1 clocks, computers or devices with a source of true Coordinated Universal Time (UTC). Typically the next level down are the top-level Network Switches, which get their time directly from the Stratum 1 device, and act as Stratum 2 servers providing time to the rest of the network.
Ethernet LANs are fast becoming the favoured network configuration for power automation systems in substations. Station bus IEC61850 has been created to provide a single, global and future-proof standard for substation communications. It facilitates a utility-wide common communication infrastructure, from the control centre to the switchyard, and allows manufacturer-independent information exchange from multivendor equipment within the automation system. IEC61850 is now ready.
If you're looking to upgrade substation communications in the future, it makes sound commercial sense to begin with the purchase of a clock for network synchronization that is already NTP equipped. The Tekron TCG01 can be optionally configured as an NTS of Stratum 1 clock capability.
If you purchase the Tekron TCG01 with NTS capability already built-in, you won't have to return it later for an upgrade, ever.
The Northern Hemisphere was shocked in 2003 when multiple blackouts occured. Two common themes have emerged following the blackout events.
Read more in this article by Geoff Vaughan from HV Power (PDF 217kb).