Sntp Server Requirements; Ptp Requirements; Iec/Uca 61850-9-2Le Merging Unit Requirements - ABB 650 series Applications Manual

Section 16
Requirements
16.3
16.4
16.5
300
The protection IED has effective filters for these transients, which gives secure and
correct operation with CVTs.

SNTP server requirements

The SNTP server to be used is connected to the local network, that is not more than
4-5 switches or routers away from the IED. The SNTP server is dedicated for its
task, or at least equipped with a real-time operating system, that is not a PC with
SNTP server software. The SNTP server should be stable, that is, either
synchronized from a stable source like GPS, or local without synchronization.
Using a local SNTP server without synchronization as primary or secondary server
in a redundant configuration is not recommended.

PTP requirements

For PTP to perform properly, the Ethernet equipment that is used needs to be
compliant with IEEE1588. The clocks used must follow the IEEE1588 standard
BMC (Best Master Algorithm) and shall, for instance, not claim class 7 for a longer
time than it can guarantee 1us absolute accuracy.

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
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