GE G30 Instruction Manual

Also see for G30: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

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5-96 G30 GENERATOR PROTECTION SYSTEM – INSTRUCTION MANUALPRODUCT SETUP CHAPTER 5: SETTINGS5The G30 supports the Precision Time Protocol (PTP) specified in IEEE Std 1588 2008 using the Power Profile (PP) specified inIEEE Std C37.238 2011. This enables the relay to synchronize to the international time standard over an Ethernet networkthat implements PP.The relay can be configured to operate on some PTP networks that are not strictly PP. Time accuracy can be less thanspecified for a PP network. Tolerated deviations from strict PP include 1) missing declaration of PP compliance in themessages, 2) connection to a network device that does not support the PTP peer delay mechanism, 3) jitter substantiallygreater 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 asversion 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 synchronizationaccuracies better than 1 ns, but this requires that each and every component in the network achieve very high levels ofaccuracy and a very high baud rate, faster than normally used for relay communications. When operating over a genericEthernet network, time error can amount to 1 ms or more. PP is a profile of PTP which specifies a limited subset of PTPsuitable for use in power system protection, control, automation, and data communication applications, and therebyfacilitates interoperability between different vendor’s clocks and switches. PP specifies a worst-case delivered time error ofless 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 synchronizationhierarchy with the “best” clock available making itself the "grandmaster" at the top of the hierarchy; all others makethemselves “slaves” and track the grandmaster. Typically the grandmaster clock receives its time from GPS satellites orsome other link to the international time standard. If the grandmaster fails, the next “best” clock available in the domainassumes the grandmaster role. When a clock on start-up discovers that it is “better” than the present grandmaster, itassumes the grandmaster role and the previous grandmaster reverts to slave. The G30 qualification mechanism accepts apotential master clock as a new grandmaster, when in a four-second interval it has received three announce messagesfrom it, all better than the present grandmaster clock and better than any other announce in this interval.Time messages issued by the grandmaster are delayed as they pass through the network both due to the finite speed ofthe signal in the interconnecting fiber or wire, and due to processing delays in the Ethernet switches. Each clock and switchimplementing PP measures the propagation delay to each of its PP neighbors, and compensates for these delays in thetime received. Each network device implementing PP measures the processing delay it introduces in each time messageand compensates for this delay in the time it transmits. As a result, the time delivered to end-devices such as the UR arevirtually identical to the grandmaster time. If one of the network devices in the hierarchy does not fully implement PP, theassociated propagation delay and/or latency may not be compensated for, and the time received at the end-device can bein error by more than 100 μs.See the preceding Real Time Clock section for a description of when time values received via PTP are used to update therelay’s real time clock.The following settings are available for configuring the relay for PTP. The PTP menu displays only when the option waspurchased.STRICT POWER PROFILE — Power profile (IEEE Std C37.238 2011) requires that the relay only select a power profile compliantclock as a grandmaster, that the delivered time have worst-case error of ±1 μs, and that the peer delay mechanism beimplemented. With the strict power profile setting enabled, the relay only selects as master the clocks displaying theIEEE_C37_238 identification codes. It uses a port only when the peer delay mechanism is operational. With the strict powerprofile setting disabled, the relay uses clocks without the power profile identification when no power profile clocks arepresent, and uses ports even if the peer delay mechanism is non-operational. This setting applies to all of the relay’s PTPcapable ports.PTP DOMAIN NUMBER — Set this setting to the domain number of the grandmaster-capable clock(s) to be synchronized to. Anetwork can support multiple time distribution domains, each distinguished with a unique domain number. Morecommonly, there is a single domain using the default domain number zero.This setting applies to all of the relay’s PTP capable ports.PTP VLAN PRIORITY — This setting selects the value of the priority field in the 802.1Q VLAN tag in request messages issuedby the relay’s peer delay mechanism. In compliance with PP the default VLAN priority is 4, but it is recommended that it beset to 7 in accordance with PTP. Depending on the characteristics of the device to which the relay is linked directly, VLANPriority can have no effect.This setting applies to all of the relay’s PTP capable ports.