Hitachi Relion 670 Series Applications Manual page 427

1MRK506375-UEN Rev. N
• Independent synchronization, asynchronous mapping
• The actual SDH port must be set to allow transmission of the master clock from the PDH-system
via the SDH-system in transparent mode.
• Maximum clock deviation <±50 ppm nominal, <±100 ppm operational
• Jitter and Wander according to ITU-T G.823 and G.825
• Buffer memory <100 μs
• Format: Transparent
• Maximum channel delay
• Loop time <40 ms continuous (2 x 20 ms)
IED with echo synchronization of differential clock (without GPS clock)
• Both channels must have the same route with maximum asymmetry of 0,2-0,5 ms, depending
on set sensitivity of the differential protection.
• A fixed asymmetry can be compensated (setting of asymmetric delay in built in HMI or the
parameter setting tool PST).
IED with GPS clock
• Independent of asymmetry.
22.6 IEC/UCA 61850-9-2LE Merging unit requirements
The merging units that supply the IED with measured values via the process bus must fulfill the
IEC/UCA 61850-9-2LE standard.
This part of the IEC 61850 is specifying "Communication Service Mapping (SCSM) – Sampled values
over ISO/IEC 8802", in other words – sampled data over Ethernet. The 9-2 part of the IEC 61850
protocol uses also definitions from 7-2, "Basic communication structure for substation and feeder
equipment – Abstract communication service interface (ACSI)". The set of functionality implemented
in the IED (IEC/UCA 61850-9-2LE) is a subset of the IEC 61850-9-2. For example the IED covers the
client part of the standard, not the server part.
The standard does not define the sample rate for data, but in the UCA users group recommendations
there are indicated sample rates that are adopted, by consensus, in the industry.
There are two sample rates defined: 80 samples/cycle (4000 samples/sec. at 50Hz or 4800 samples/
sec. at 60 Hz) for a merging unit "type1" and 256 samples/cycle for a merging unit "type2". The IED
can receive data rates of 80 samples/cycle.
Note that the IEC/UCA 61850-9-2LE standard does not specify the quality of the sampled values,
only the transportation. Thus, the accuracy of the current and voltage inputs to the merging unit and
the inaccuracy added by the merging unit must be coordinated with the requirement for actual type of
protection function.
Factors influencing the accuracy of the sampled values from the merging unit are for example anti
aliasing filters, frequency range, step response, truncating, A/D conversion inaccuracy, time tagging
accuracy etc.
In principle the accuracy of the current and voltage transformers, together with the merging unit, shall
have the same quality as direct input of currents and voltages.
Railway application RER670
Application manual
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Section 22
Requirements
SEMOD166590-11 v5
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