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8 SERIES PROTECTIVE RELAY PLATFORM – COMMUNICATIONS GUIDE
REAL-TIME CLOCK
CHAPTER 3: TIME PROTOCOLS
IEEE 1588 Precision Time Protocol (PTP)
PTP Status
The present values of the PTP protocol are displayed here.
Path
:
Status > PTP
The
RTC Sync Source
actual value is the time synchronizing source the relay is using at
present. Possible sources are: Port 4 PTP Clock, Port 5 PTP Clock, IRIG-B, SNTP and None.
Grandmaster ID
is the grandmaster Identity code being received from the present PTP
grandmaster, if any. When the relay is not using any PTP grandmaster, this actual value is
zero. The grandmaster Identity code is specified by PTP to be globally unique, so one can
always know which clock is grandmaster in a system with multiple grandmaster-capable
clocks.
RTC Accuracy
is the estimated maximum time difference at present in the Real Time Clock
(RTC), considering the quality information imbedded in the received time signal, how long
the relay has had to lock to the time source, and in the case of time signal interruptions,
the length of the interruption. The value 999,999,999 indicates that the magnitude of the
estimated difference is one second or more, or that the difference cannot be estimated.
Port 4 (5) PTP State
is the present state of the port’s PTP clock. The PTP clock state is:
•
DISABLED
If the port’s function setting is Disabled
•
NO SIGNAL
If enabled but no signal from an active master has been found and selected
•
CALIBRATING
If an active master has been selected but lock is not at present established
•
SYNCH’D (NO PDELAY)
If the port is synchronized, but the peer delay mechanism is non-operational
•
SYNCHRONIZED
If the port is synchronized
PTP Configuration
Path
:
Setpoints > Device > Real Time Clock > Precision Time
PORT 4(5) PTP FUNCTION
Range: Disabled, Enabled
Default: Enabled
When the port setting is selected as “Disabled,” PTP is disabled on the port. The relay
does not generate, or listen to, PTP messages on the port.
PORT 4(5) PATH DELAY ADDER
Range: 0 to 60000 ns in steps of 1 ns
Default: 0 ns
The time delivered by PTP is advanced by the time value in the setting prior to the time
being used to synchronize the relay’s real time clock. This is to compensate for time
delivery delays not compensated for in the network. In a fully compliant Power Profile
(PP) network, the peer delay and the processing delay mechanisms compensate for all
the delays between the grandmaster and the relay. In such networks, the setting is zero.
In networks containing one or more switches and/or clocks that do not implement both
of these mechanisms, not all delays are compensated, so the time of message arrival at
the relay is later than the time indicated in the message. The setting can be used to
approximately compensate for the delay. Since the relay is not aware of network
switching that dynamically changes the amount of uncompensated delay, there is no
setting that always completely corrects for uncompensated delay. A setting can be
chosen that reduces worst-case error to half of the range between minimum and
maximum uncompensated delay if these values are known.
