• Independent synchronization, asynchronous mapping• The actual SDH port must be set to allow transmission of the master clockfrom 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 0,2-0,5ms, depending on set sensitivity of the differential protection.• A fixed asymmetry can be compensated (setting of asymmetric delay in builtin HMI or the parameter setting tool PST).IED with GPS clock• Independent of asymmetry.24.6 IEC/UCA 61850-9-2LE Merging unit requirementsSEMOD166590-11 v5The merging units that supply the IED with measured values via the process busmust 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 dataover Ethernet. The 9-2 part of the IEC 61850 protocol uses also definitions from7-2, “Basic communication structure for substation and feeder equipment –Abstract communication service interface (ACSI)”. The set of functionalityimplemented in the IED (IEC/UCA 61850-9-2LE) is a subset of the IEC61850-9-2. For example the IED covers the client part of the standard, not theserver part.The standard does not define the sample rate for data, but in the UCA users grouprecommendations 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 50Hzor 4800 samples/sec. at 60 Hz) for a merging unit “type1” and 256 samples/cyclefor 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 thesampled values, only the transportation. Thus, the accuracy of the current andvoltage inputs to the merging unit and the inaccuracy added by the merging unitmust be coordinated with the requirement for actual type of protection function.Section 24 1MRK 511 401-UEN ARequirements608 Bay control REC670 2.2 IECApplication manual
