What is NTP?
NTP runs over an IP network and corrects client clocks against a reference time server. By measuring the round-trip delay between server and client it compensates for network latency, achieving millisecond accuracy on a local network and microsecond accuracy in well-engineered systems. NTP is hierarchical: servers connected directly to a reference clock (GPS, atomic clock) are “stratum 1”, and those taking time from them are “stratum 2”.
Why it matters in the energy sector
Fault analysis at a substation depends on knowing the order in which events occurred. If the clocks of protection relays, the RTU, fault recorders and the SCADA server drift apart, the Sequence of Events (SOE) records become meaningless and the root cause of the fault cannot be established. Every intelligent electronic device (IED) at the site must therefore be fed from a single time server.
Typical time server specifications
- Time source
- GPS / GNSS antenna synchronisation — stratum 1 operation
- Holdover
- Accuracy maintained by an internal oscillator when the antenna signal is lost
- Protocols
- NTPv4, SNTP; PTP (IEEE 1588) and IRIG-B where required
- Interfaces
- Ethernet (RJ45 or SFP); redundant network port option
- Time outputs
- IRIG-B, 1PPS, serial time code — for legacy equipment
- Standards
- Compatible with IEC 61850 based substation automation
- Supply
- 48 / 110 / 220 VDC or 220 VAC; redundant supply option
- Mounting
- 19" rack mount, 1U
Systems that benefit from time synchronisation
- Protection relays and IEDs
- RTUs and SCADA servers
- Fault recorders
- Power analysers and meters
- Industrial switches and network equipment
- CCTV and security systems