Time Delay; Blocking; Design - ABB REG650 Technical Manual

1MRK 502 034-UEN -
9.1.7.2
9.1.7.3
9.1.7.4
Technical Manual
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 of the global parameter UBase.
To avoid oscillations of the output START signal, a hysteresis has been included.

Time delay

The time delay for SAPTUF is a settable definite time delay, specified by the
setting tDelay.
Trip signal issuing requires that the under frequency condition continues for at least
the user set time delay. If the START condition, with respect to the measured
frequency ceases during the delay time, and is not fulfilled again within a defined
reset time, the START output is reset.
On the RESTORE output of SAPTUF a 100 ms pulse is issued, after a time delay
corresponding to the setting of tRestore, when the measured frequency returns to
the level corresponding to the setting RestoreFreq.

Blocking

It is possible to block underfrequency protection SAPTUF completely, by binary
input signal:
BLOCK: blocks all outputs
If the measured voltage level decreases below the setting of MinValFreqMeas in
the preprocessing function, both the START and the TRIP outputs, are blocked.

Design

The frequency measuring element continuously measures the frequency of the
positive sequence voltage and compares it to the setting StartFrequency. The
frequency signal is filtered to avoid transients due to switchings and faults in the
power systems. When the frequency has returned back to the setting of
RestoreFreq, the RESTORE output is issued after the time delay tRestore. The
design of Under frequency protection SAPTUF is schematically described in
figure 132.
Section 9
Frequency protection
257