ABB RELION RET670 Applications Manual page 125

1MRK 504 163-UUS A
Transformer protection RET670 2.2 ANSI
Application manual
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 14: PMUREPORT Monitored data
Name Type
TIMESTAT BOOLEAN
FREQ REAL
FREQGRAD REAL
Table continues on next page
Wide area measurement system
Values (Range) Unit
1=Ready -
0=Fail
- Hz
- -
Section 6
PID-6244-MONITOREDDATA v2
Description
Time synchronization status
Frequency
Rate of change of frequency
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