DCF77 Protocol Description
DCF77 is a time synchronization protocol with its origin in Europe. DCF77 was developed by the Physikalisch-Technische Bundesanstalt (PTB), the national institute for science and technology in Germany. Historically, DCF77 has been used to synchronize power system devices, such as breakers, relays and meters, by Schneider Electric, Eaton and others.
DCF77 is typically distributed at 24V as a DC level shift (DCLS), pulse-width coded signal that provides a complete date/time string once every minute. Like IRIG-B, DCF77 is used for time sync, accurate to 100 microseconds in reference to UTC (Coordinated Universal Time).
For more details on DCF77 protocol and its applications, see Tech Note: Overview of DCF77 Time Protocol (TN-103)
Time Sync: PowerXpert™ Meters: PXM 4000-6000-8000
Modern industrial/commercial power systems require precise time synchronization of all devices to ensure meaningful data for analysis and reliable operation. PowerXpert PXM 4000-6000-8000 meters from Eaton support DCF77 protocol for precision time sync. CyTime™ SER-3200/2408 Sequence of Events Recorders from Cyber Sciences can generate DCF77 to synchronize these meters, greatly simplifying time sync design. SER-3200/2408 Event Recorders accept a variety of time source options and then sync with each other using PTP. In turn, a PTP slave can also output a legacy protocol (e.g., DCF77) to devices that do not support PTP (e.g., PowerXpert meters).
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PowerXpert Meter Time-Sync Wiring
PowerXpert meters (PXM 4000-6000-8000) can decode a DCF77 time sync signal via a dedicated digital input. To take advantage of PTP (IEEE 1588) precision time sync over Ethernet, an SER-3200-PTP (or SER-2408-PTP) is configured as a time sync master with DCF77 as its output (via PLX-24V). Because the DCF77 signal is distributed at 24 Vdc and PowerXpert meters' digital inputs are powered internally, the DCF77 signal must be connected to one of the digital inputs through an interposing relay. Eaton literature recommends Phoenix Contact Optocoupler, part number PLC-OSC- 24DC/ 48DC/100/C1D2, order key 5603261.
PowerXpert Meter Setup
When using DCF77 for time synchronization, the digital input used for time sync must be configured for DCF77. For more details on PowerXpert meters, please contact Eaton Corporation.
► For more details, see Tech Note: Overview of DCF77 Time Protocol (TN-103)