ABB REG650 ANSI, Technical Manual

Page: 303 / 728

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 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 system. 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 of the global parameter
UBase .
To avoid oscillations of the output START signal, a hysteresis has been included.
Frequency Comparator
f < StartFrequency
START
START
TRIP
BLOCK
Comparator
f > RestoreFreq
BLOCK
OR
DefiniteTimeDelay
TimeDlyOperate
TimeDlyRestore
RESTORE
100 ms
Start
&
Trip
Output
Logic
IEC09000034-1.vsd
TRIP
BLKDMAGN
freqNotValid
IEC09000034 V1 EN
Figure 149: Simplified logic diagram for SAPTUF
10.1.7.2 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 ceases during the delay time, and is not fulfilled
again within a defined reset time, the START output is reset.
1MRK 502 048-UEN A
Section 10
Frequency protection
297
Technical manual