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.
1MRK 502 071-UEN - Section 24
Requirements
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 761
Application manual
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