GE 845 Instruction Manual page 117

CHAPTER 4: SETPOINTS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL
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.
PORT 4(5) PATH DELAY ASYMMETRY
Range: -1000 to +1000 ns in steps of 1 ns
Default: 0 ns
The setting corresponds to "Delay Asymmetry" in PTP, which is used by the peer delay
mechanism to compensate for any difference in the propagation delay between the two
directions of a link. Except in unusual cases, the two fibers are of essentially identical
length and composition, so the setting is set to zero.
In unusual cases where the length of link is different in different directions, the setting is
to be set to the number of nanoseconds longer the Ethernet propagation delay is to the
relay compared with the mean of path propagation delays to and the from the relay. For
instance, if it is known say from the physical length of the fibers and the propagation
speed in the fibers that the delay from the relay to the Ethernet switch it is connected to
is 9000 ns and that the delay from the switch to the relay is 11000 ns, then the mean
delay is 10000 ns, and the path delay asymmetry is +1000 ns.
STRICT POWER PROFILE
Range: Enabled, Disabled
Default: Enabled
Power profile (IEEE Std C37.238™ 2011) requires that the relay select as a grandmaster
only power profile compliant clocks, that the delivered time have a worst-case error of
±1 µs, and that the peer delay mechanism be implemented. With the strict power profile
setting enabled, the relay selects as master only clocks displaying the IEEE_C37_238
identification codes. It uses a port only when the peer delay mechanism is operational.
With the strict power profile setting disabled, the relay uses clocks without the power
profile identification when no power profile clocks are present, and uses ports even if
the peer delay mechanism is non-operational.
The setting applies to all of the relay's PTP-capable ports.
PTP DOMAIN NUMBER
Range: 0 to 255
Default: 0
The setting is set to the domain number of the grandmaster-capable clock(s) to which
they can be synchronized. A network may support multiple time distribution domains,
each distinguished with a unique domain number. More commonly, there is a single
domain using the default domain number zero.
The setting applies to all of the relay's PTP-capable ports.
DEVICE
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