Hitachi Relion 670 Series Applications Manual page 411

1MRK506375-UEN Rev. N
21.10.2 Setting guidelines
Remember always that there are two possible ways to place the IED in the TestMode= On" state. If,
the IED is set to normal operation (TestMode = Off), but the functions are still shown being in the test
mode, the input signal IED_TEST on the TESTMODE function block is activated in the configuration.
Forcing of binary input and output signals is only possible when the IED is in IED test mode.
21.11 Time synchronization TIMESYNCHGEN
21.11.1 Application
Use time synchronization to achieve a common time base for the IEDs in a protection and control
system. This makes it possible to compare events and disturbance data between all IEDs in the
system. If a global common source (i.e. GPS) is used in different substations for the time
synchronization, also comparisons and analysis between recordings made at different locations can
be easily performed and a more accurate view of the actual sequence of events can be obtained.
Time-tagging of internal events and disturbances are an excellent help when evaluating faults.
Without time synchronization, only the events within one IED can be compared with each other. With
time synchronization, events and disturbances within the whole network, can be compared and
evaluated.
In the IED, the internal time can be synchronized from the following sources:
• GPS
• IRIG-B
• IEEE 1588 (PTP)
For IEDs using IEC/UCA 61850-9-2LE in "mixed mode" a time synchronization from an external
clock is recommended to the IED and all connected merging units. The time synchronization from the
clock to the IED can be PTP, optical PPS or IRIG-B. For IEDs using IEC/UCA 61850-9-2LE from one
single MU as analog data source, the MU and IED still need to be synchronized to each other. This
could be done by letting the MU supply a PPS signal to the IED or by supplying a PPS signal from
the IED to the MU, by using a GTM.
The selection of the time source is done via the corresponding setting.
It is possible to set a backup time-source for GPS signal, for instance SNTP. In this case, when the
GPS signal quality is bad, the IED will automatically choose SNTP as the time-source. At a given
point in time, only one time-source will be used.
If PTP is activated, the device with the best accuracy within the synchronizing group will be selected
as the source. For more information about PTP, see the Technical manual.
IEEE 1588 (PTP)
PTP according to IEEE 1588-2008 and specifically its profile IEC/IEEE 61850-9-3 for power utility
automation is a synchronization method that can be used to maintain a common time within a station.
This time can be synchronized to the global time using, for instance, a GPS receiver. If PTP is
enabled on the IEDs and the switches that connect the station are compatible with IEEE 1588, the
station will become synchronized to one common time with an accuracy of under 1us. Using an IED
as a boundary clock between several networks will keep 1us accuracy on three levels or when using
an HSR, 15 IEDs can be connected in a ring without losing a single microsecond in accuracy.
Railway application RER670
Application manual
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Section 21
Basic IED functions
M15260-3 v7
IP1750-1 v2
M11345-3 v13
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