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15.16
SEL-400 Series Relays
Instruction Manual
Date Code 20171006
Communications Interfaces
Ethernet Communications
NOTE:
The SEL-2488 with the PTP
option is a PTP grandmaster clock
capable GPS receiver.
In PTP, a clock that provides time to other devices, typically based on GPS input,
is a master clock. The intervening switches are transparent clocks. It is also possi-
ble to connect networks together and pass time from one network to another
using boundary clocks. Transparent and boundary clocks are important because
they provide time correction in the PTP messages that pass through them,
whereas devices that are not 1588 aware would not provide this correction.
Because it is possible for a network to have multiple master clocks, PTP clocks
implement algorithms to select the best available clock. The one selected for use
by an end device is the grandmaster clock. A complete description of possible
PTP networking configurations is beyond the scope of this manual. You can learn
more about configuring a PTP network in these application guides:
“Using the SEL-2488 to Provide IEEE 1588 Version 2 Grandmaster Func-
tionality in a Redundant Network Topology” (AN2015-07)
“Using the SEL-2488 to Provide IEEE 1588 Version 2 Grandmaster Func-
tionality to Isolated Ethernet Networks” (AN2015-06)
NOTE:
PTP is not available when
Parallel Redundancy Protocol (PRP) is
enabled.
To configure PTP, update the Port 5 PTP settings as described in
. By
default, PTP is disabled in the relay. Set EPTP to Y to enable PTP and make the
other PTP settings available.
Within PTP, there are multiple clock profiles available. A profile defines the set
of PTP features available in a specific application domain. SEL-400 series relays
support two profiles: Default and Power System profile (C37.238-2011).
The Default profile has many optional features. It was intended to address com-
mon applications, so has been implemented by most PTP capable devices. The
Default profile supports both UDP or layer 2 (802.3) Ethernet transport, and can
use either end-to-end (E2E) or peer-to-peer (P2P) Delay Mechanism. Grandmas-
ter clocks can send Announce, Sync, and Delay request messages over a wide
range of intervals. A Default profile network can consist of boundary clocks or
transparent clocks anywhere between the grandmaster and the end devices. The
only performance requirement for the Default profile is that a master clock must
maintain frequency accurate to within 0.01%. A well designed Default profile
network with an accurate grandmaster can come close to the 1
s accuracy avail-
able to Power profile networks.
The Power profile was created to minimize the number of optional features to
facilitate interoperability and predictable performance in order to provide the
required time accuracy for Synchrophasors and for SCADA. The Power profile is
only supported on layer 2 networks and exclusively uses the peer-to-peer Delay
Mechanism. All messages must be sent at 1-second intervals, must have 802.1Q
VLAN tags, and announce messages must include grandmaster ID and (maxi-
mum) inaccuracy fields. Transparent clocks are mandatory in a power profile net-
work; boundary clocks are not allowed. For a network with less than 16 hops
between Grandmaster and IED, the Power profile can deliver time with better
accuracy than 1
s. Select the profile using the PTPPRO setting.
PTP defines a logical grouping of clocks in a network as a clock domain. This
allows a logical separation between clocks that participate in different application
domains to coexist on the same network. Domains are identified by domain num-
bers. The domain number for the relay is selected by the DOMNUM setting. Set
DOMNUM to match the domain number configured in the master clocks the
relay should synchronize with.
The relay supports transport of PTP messages over UDP or layer 2 (Ethernet).
Use the PTPTR setting to select the PTP transport mechanism. This needs to
match the transport mechanism used in the master clocks. Only layer 2 is avail-
able with the Power System profile. If operating in a UDP network, PTP will
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