VAMP 52 - 2.18. Single-phase undervoltage protection U< (27)

2.18 Single-phase undervoltage
protection U< (27)
2 Protection functions Technical description
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Parameter Value Unit Default Description
S_Off
Enabled;
Disabled
- Enabled Start off event
T_On
Enabled;
Disabled
- Enabled Trip on event
T_Off
Enabled;
Disabled
- Enabled Trip off event
Measured and recorded values of single-phase overvoltage
stages U>, U>>, U>>> (59):
Parameter Value Unit Description
Measured
value
Umax V
Maximum value of line
voltages
SCntr - Start counter (Start) reading
TCntr - Trip counter (Trip) reading
Flt %Un The max. fault value
Recorded
values
EDly %
Elapsed time as compared to
the set operating time; 100% =
tripping
2.18. Single-phase undervoltage protection
U< (27)
NOTE! Available when the voltage measurement mode is 1LL or 1LN.
The single-phase undervoltage function consists of three
separately adjustable undervoltage stages (stage U<, U<< and
U<<<).
The device measures the fundamental frequency component of
a single phase-to-neutral (1LN) or a line-to-line (1LL) voltage.
Then the three-phase voltage calculation is done, assuming
that all the voltages are symmetrical, i.e. no zero sequence
voltage is present. The protection stages operate with definite
time characteristics.
The function starts, if the measured or calculated line-to-line
voltage drops below the setting value. If the undervoltage
situation continues after the start delay has elapsed, the
function trips.
The undervoltage stage U< has a settable release delay, which
enables detecting instantaneous faults. This means that the
time counter of the protection function does not reset
immediately after the fault is cleared, but resets only after the
release delay has elapsed. If the fault appears again before the
delay time has elapsed, the trip counter continues from the
previous fault value. This means that the function trips after a
certain number of instantaneous faults.