GE L30 Instruction Manual page 324

PRODUCT SETUP
5.3.7.2 Precision time protocol (1588)
SETTINGS  PRODUCT SETUP  REAL TIME CLOCK  PRECISION TIME PROTOCOL (1588)
 PRECISION TIME
 PROTOCOL (1588)
SETTINGS  PRODUCT SETUP  REAL TIME CLOCK  PRECISION TIME PROTOCOL (1588)  PTP PORT 1(3)
 PTP PORT 1

The L30 is provided with optional Precision Time Protocol capability. This feature is specified as the IEEE 1588
5
software option at the time of ordering. See the Order Codes section in chapter 2 for details.
The L30 supports the Precision Time Protocol (PTP) specified in IEEE Std 1588 2008 using the Power Profile (PP) specified in
IEEE Std C37.238 2011. This enables the relay to synchronize to the international time standard over an Ethernet network
that implements PP.
The relay can be configured to operate on some PTP networks that are not strictly PP. Time accuracy can be less than
specified for a PP network. Tolerated deviations from strict PP include 1) missing declaration of PP compliance in the
messages, 2) connection to a network device that does not support the PTP peer delay mechanism, 3) jitter substantially
greater than 1 µs in received event messages, and 4) certain non-compliant announce and sync message update rates.
The relay implements PTP according to IEEE Std 1588 2008 and the equivalent IEC 61588:2009(E), sometimes referred to as
version 2 PTP. It does not support the previous version of the standard (version 1).
PTP is a protocol that allows multiple clocks in a network to synchronize with one another. It permits synchronization
accuracies better than 1 ns, but this requires that each and every component in the network achieve very high levels of
accuracy and a very high baud rate, faster than normally used for relay communications. When operating over a generic
Ethernet network, time error can amount to 1 ms or more. PP is a profile of PTP which specifies a limited subset of PTP
suitable for use in power system protection, control, automation, and data communication applications, and thereby
facilitates interoperability between different vendor's clocks and switches. PP specifies a worst-case delivered time error of
less than 1 µs over a 16-hop network.
In a PTP system and in a PP system, the clocks automatically organize themselves into a master-slave synchronization
hierarchy with the "best" clock available making itself the "grandmaster" at the top of the hierarchy; all others make
themselves "slaves" and track the grandmaster. Typically the grandmaster clock receives its time from GPS satellites or
some other link to the international time standard. If the grandmaster fails, the next "best" clock available in the domain
assumes the grandmaster role. When a clock on start-up discovers that it is "better" than the present grandmaster, it
assumes the grandmaster role and the previous grandmaster reverts to slave. The L30 qualification mechanism accepts a
potential master clock as a new grandmaster, when in a four-second interval it has received three announce messages
from it, all better than the present grandmaster clock and better than any other announce in this interval.
5-110
STRICT POWER

PROFILE: Disabled
PTP DOMAIN NUMBER:

0
PTP VLAN PRIORITY:

4
PTP VLAN ID:

0
 PTP PORT 1


PORT 1 PTP FUNCTION:

Disabled
PORT 1 PATH DELAY

ADDER: 0 ns
PORT 1 PATH DELAY

ASYMMETRY: 0 ns
Range: Enabled, Disabled
Range: 0 to 255
Range: 0 to 7
Range: 0 to 4095
See below
Range: Enabled, Disabled
Range: 0 to 60000 ns in steps of 1
Range: –1000 to +1000 ns in steps of 1
L30 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 5: SETTINGS