GE L30 Instruction Manual

Also see for L30: Communications manual Communications guide Instruction manual Instruction manual Instruction manual

Contents

5-66 L30 Line Current Differential System GE Multilin5.2 PRODUCT SETUP 5 SETTINGS5PATH: SETTINGS  PRODUCT SETUP  REAL TIME CLOCK  PRECISION TIME PROTOCOL (1588)  PTP PORT 1(3)The UR supports the Precision Time Protocol (PTP) specified in IEEE Std 1588 2008 using the Power Profile (PP) specifiedin IEEE Std C37.238 2011. This enables the relay to synchronize to the international time standard over an Ethernet net-work that 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 the mes-sages, 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), sometimesreferred 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 accu-racies better than 1 ns, but this requires each and every component in the network achieve very high levels of accuracy anda very high baud rate, faster than normally used for relay communications. When operating over a generic Ethernet net-work, time error may amount to 1 ms or more. PP is a profile of PTP which specifies a limited subset of PTP suitable for usein power system protection, control, automation and data communication applications, and thereby facilitates interoperabil-ity between different vendor’s clocks and switches. PP specifies a worst-case delivered time error of less than 1 μs over a16-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 make them-selves “slaves” and track the grandmaster. Typically the grandmaster clock receives its time from GPS satellites or someother link to the international time standard. If the grandmaster fails, the next “best” clock available in the domain assumesthe grandmaster role. Should a clock on starting up discover it is “better” that the present grandmaster, it assumes thegrandmaster role and the previous grandmaster reverts to slave. The L30 qualification mechanism accepts a potential mas-ter clock as a new grandmaster, when in a four-second interval it has received three announce messages from it, all betterthan 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. Should one of the network devices in the hierarchy not fully implement PP, theassociated propagation delay and/or latency may not be compensated for, and the time received at the end-device could bein error by more than 100 μs.See the Settings > Product Setup > Real Time Clock section of this manual for a description of when time valuesreceived via PTP are used to update the relay’s real time clock.The following settings are available for configuring the relay for PTP.STRICT POWER PROFILE• Power profile (IEEE Std C37.238 2011) requires that the relay only select as a grandmaster power profile compliantclocks, that the delivered time have worst-case error of ±1 μs, and that the peer delay mechanism be implemented.With the strict power profile setting enabled, the relay will only select as master clocks displaying the IEEE_C37_238identification codes. It will use a port only when the peer delay mechanism is operational. With the strict power profilesetting disabled, the relay will use clocks without the power profile identification when no power profile clocks are pres-ent, and will use ports even if the peer delay mechanism is non-operational.• This setting applies to all of the relay’s PTP capable ports.MESSAGE PORT 1 PTP FUNCTION:DisabledRange: Enabled, DisabledMESSAGE PORT 1 PATH DELAYADDER: 00000 nsRange: 0 to 60 000 ns in steps of 1MESSAGE PORT 1 PATH DELAYASYMMETRY: 0000 nsRange: –1 000 to +1 000 ns in steps of 1NOTE