T&D World Magazine
Submicrosecond Accuracy Added to Network Clock

Submicrosecond Accuracy Added to Network Clock

With multiple protocol options, one network clock can meet a wide range of application needs.

Schweitzer Engineering Laboratories, Inc. (SEL) has added support for the Precision Time Protocol (PTP) to the SEL-2488 Satellite-Synchronized Network Clock. In just one clock, users can now synchronize end devices with submicrosecond accuracy using demodulated IRIG-B and/or PTP. The SEL-2488 can meet all the timing needs of industrial and utility applications.

In addition to providing IRIG-B and NTP outputs, the SEL-2488 can now serve as a PTP grandmaster clock, supporting both the default profile (IEEE 1588-2008) and the power system profile (IEEE C37.238). The SEL-2488 is capable of synchronizing time for up to four independent networks with a time-stamp accuracy of 100 nanoseconds. Existing users of the SEL-2488 can purchase this as a firmware upgrade.

“Now there’s a choice,” said Shankar Achanta, R&D manager for precise time and wireless networks at SEL. “You can use different timing protocols based on your infrastructure and application needs. The SEL-2488 is the one network clock that can meet all our customers’ timing needs.”


The SEL-2488 was first released in September 2014. SEL included several security features in the SEL-2488 that other critical infrastructure clocks don’t offer, such as Syslog, the Ethernet standard for event messaging, which allows the SEL-2488 to integrate smoothly into a customer’s existing event system; role-based accounts and Lightweight Directory Access Protocol (LDAP) for user authentication; and a secure HTTPS web interface, which provides a graphical SkyView™ display for troubleshooting signal or antenna issues. The SEL-2488 also meets and exceeds IEEE 1613 Class 1, an electric transient and interference standard for communications products.

The SEL-2488 offers additional security features, including Satellite Signal Verification in which the clock uses two satellite constellations to validate time signals, providing a layer of protection from GPS spoofing attacks. For fault tolerance, customers can opt for a second, redundant hot-swappable power supply, which can be connected to a second power input source. If GPS is lost, the clock switches to a standard TCXO holdover with 36-microsecond-per-day accuracy or an optional OCXO holdover with 5 microsecond average accuracy. The clock operates over a wide temperature range of –40° to +85°C (–40° to +185°F) and is backed by SEL’s 10-year, no-questions-asked worldwide warranty.


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