4.3 IEC 61850-9-2LE communication protocol
4.3.1 Introduction
Every IED can be provided with a communication interface enabling it to connect to a
process bus, in order to get data from analog data acquisition units close to the process
(primary apparatus), commonly known as Merging Units (MU). The protocol used in
this case is the IEC 61850-9-2LE communication protocol.
Note that the IEC 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 shall the accuracy of the current and voltage transformers, together with
the merging unit, have the same quality as direct input of currents and voltages.
The process bus physical layout can be arranged in several ways, described in Annex B
of the standard, depending on what are the needs for sampled data in a substation.
1MRK504116-UUS C Section 4
Station communication
817
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