ABB REG670 - Monitored Data

Table 307: SAPTUF Non group settings (basic)
Name Values (Range) Unit Step Default Description
GlobalBaseSel 1 - 12 - 1 1 Selection of one of the Global Base Value
groups
10.1.6 Monitored data
Table 308: SAPTUF Monitored data
Name Type Values (Range) Unit Description
ULevel REAL - kV Level of measured
voltage
FREQ REAL - Hz Measured frequency
10.1.7 Operation principle
Underfrequency protection SAPTUF is used to detect low power system frequency.
SAPTUF can either have a definite time delay or a voltage magnitude dependent time
delay. If the voltage magnitude dependent time delay is applied, the time delay will be
longer if the voltage is higher, and the delay will be shorter if the voltage is lower. If
the frequency remains below the set value for a time period corresponding to the
chosen time delay, the corresponding trip signal is issued. To avoid an unwanted trip
due to uncertain frequency measurement at low voltage magnitude, a voltage
controlled blocking of the function is available from the preprocessing function, that
is, if the voltage is lower than the set blocking voltage in the preprocessing function,
the function is blocked and no START or TRIP signal is issued.
10.1.7.1 Measurement principle
The fundamental frequency of the measured input voltage is measured continuously,
and compared with the set value, StartFrequency. The frequency function is
dependent on the voltage magnitude. If the voltage magnitude decreases below the
setting MinValFreqMeas in the SMAI preprocessing function, which is described in
the Basic IED Functions chapter and is set as a percentage of a global base voltage
parameter, SAPTUF gets blocked, and the output BLKDMAGN is issued. All voltage
settings are made in percent of the setting UBase, which should be set as a phase-phase
voltage in kV.
To avoid oscillations of the output START signal, a hysteresis has been included.
10.1.7.2 Time delay
The time delay for underfrequency protection SAPTUF can be either a settable
definite time delay or a voltage magnitude dependent time delay, where the time delay
depends on the voltage level; a high voltage level gives a longer time delay and a low
1MRK502052-UEN B Section 10
Frequency protection
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Technical manual