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Chapter 1 – Introduction
GNSS
PTP / SNTP / NTP
Parallel Redundancy Protocol (PRP)
Stationary Mode
RT430/434
The demand for accurate time synchronization available 24/7 increases with the
growth of critical substation applications, such as phasor measurement, merging
units, traveling-wave fault location and current differential protection operating over
SONET and MPLS systems. RT430/434 GNSS now tracks GPS and GLONASS satellites
concurrently, and whenever one constellation is lost, or reports bad quality, the clock
will continue running in full synchronization based on the healthy source (with zero
switchover time). Using GNSS is also a great way to guarantee time availability when
the antenna is installed in places close to buildings or mountains, as the clock has
more satellites as time reference, offering greater immunity to "shadow" effects.
The Reason RT430/434 offers the accurate PTP time protocol, which is defined by the
IEEE 1588 standard, to precisely synchronize IED's and computers over a LAN (or
VLAN). Besides, using PTP is a great solution to synchronize multiple clocks with a
better than 100ns time accuracy over Ethernet networks.
As designed by the IEEE 1588, RT430/434 may operate either as the "PTP
Grandmaster" clock or "Slave" clock. For power applications, Reason clocks support
both the PTP Power Profile (IEEE C37.238:2011) and the PTP Profile for Power Utility
Automation (IEC 61850-9-:2016).
To save time and reduce costs by avoiding the need to overlay a separate time-
synchronizing network, SNTP/NTP and PTP can share the same physical links as IEC
61850, DNP3 over Ethernet, MODBUS, etc.
The RT430 is the first Grandmaster clock to offer Parallel Redundancy Protocol (PRP).
Profit from the high-availability, reliability, and security of your Ethernet network to
distribute time accurately and economically over the same network used on your
digital substation. The Parallel Redundancy Protocol (PRP) is in accordance with IEC
62439-3.
PRP may be use by any Ethernet protocol communication (including PTP, NTP, SNTP).
When using PTP on PRP networks, the equipment can execute a BMC (Best Master
Clock) algorithm in each port separately, calculating the link delays and responding
to PTP management messages independently. Thus, besides the PTP redundancy on
PRP networks, the RT430 compares the time quality between the two networks, to
ensure the best time accuracy.
In mostly applications, the equipment providing the time synchronization must be in
locked state. For this reason, the Stationary Mode allows the equipment to be in a
locked state even when receiving signals from a single satellite.
However, these two conditions are necessary to use the Stationary Mode:
Stationary Mode can be used only when RT430/434 is in a fixed position (in a
substation, for example). If the unit is moved from its position when operation in
Stationary Mode, there will be loss of time accuracy.
Before operating in Stationary Mode, RT430/434 must lock its sync receiving
information from at least four satellites. This condition applies every time the
unit is powered on.
RT430/434
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