This adaptive filtering is ensured by proper configuration and settings of all relevant pre-
processing blocks, see Signal matrix for analog inputs in the Application manual. Note
that in all preconfigured IEDs such configuration and settings are already made and the
three-phase voltage are used as master for frequency tracking. With such settings the IED
will be able to properly estimate the magnitude and the phase angle of measured current
and voltage phasors in this wide frequency range.
One of the important functions of a PMU is reporting a very accurate system frequency to
the PDC client. In the IED, each of the PMUREPORT instances is able to report an
accurate frequency. Each voltage-connected preprocessor block (SMAI block) delivers
the frequency data, derived from the analog input AC voltage values, to the respective
voltage phasor channel. Every phasor channel has a user-settable parameter
(PhasorXUseFreqSrc) to be used as a source of frequency data for reporting to the PDC
client. It is very important to set this parameter to On for the voltage-connected phasor
channels. There is an automatic frequency source selection logic to ensure an
uninterrupted reporting of the system frequency to the PDC client. In this frequency
source selection logic, the following general rules are applied:
• Only the voltage phasor channels are used
• The phasor channel with a lower channel number is prioritized to the one with a
higher channel number
As a result, the first voltage phasor is always the one delivering the system frequency to
the PDC client and if, by any reason, this voltage gets disconnected then the next available
voltage phasor is automatically used as the frequency source and so on. If the first voltage
phasor comes back, since it has a higher priority compare to the currently selected phasor
channel, after 500 ms it will be automatically selected again as the frequency source.
There is also an output available on the component which shows if the reference frequency
is good, error or reference channel unavailable.
It is possible to monitor the status of the frequency reference channel (frequency source)
for the respective PMUREPORT instance on Local HMI under Test/Function status/
Communication/Station Communication/PMU Report/PMUREPORT:1/Outputs,
where the FREQREFCHSEL output shows the selected channel as the reference for
frequency and FREQREFCHERR output states if the reference frequency is good, or if
there is an error or if the reference channel is unavailable. For more information refer to
the table PMUREPORT monitored data.
Table 15: PMUREPORT Monitored data
Name
Type Values (Range) Unit Description
TIMESTAT BOOLEAN 1=Ready
0=Fail
- Time synchronization status
FREQ REAL - Hz Frequency
FREQGRAD REAL - - Rate of change of frequency
Table continues on next page
1MRK 506 369-UUS - Section 6
Wide area measurement system
Line distance protection REL670 2.2 ANSI 119
Application manual
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