2.17 Single-phase overvoltage
protection U> (59)
2 Protection functions
Technical description
84
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VM50.EN004
Parameter Value
Unit Description
Note
Imax40
%Imode Allowed load at Tamb +40
C. Default = 100 %.
Set
Imax70
%Imode Allowed load at Tamb +70
C.
Set
Tamb
C
Ambient temperature.
Editable Samb=n/a. Default
= +40
C
Set
Samb
n/a
ExtAI1...
16
Sensor for ambient
temperature
No sensor in use for Tamb
External Analogue input
1...16
Set
For details of setting ranges see chapter 9.3.
Set = An editable parameter (password needed)
C = Can be cleared to zero
F = Editable when force flag is on
2.17.
Single-phase overvoltage protection
U> (59)
NOTE! Available when the voltage measurement mode is 1LL or 1LN.
The single-phase overvoltage function consists of three
separately adjustable overvoltage 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 value exceeds the setting
value. If an overvoltage situation continues after the operation
time has elapsed, the function trips.
The overvoltage stages have a fixed start delay. If a delayed
alarm about a voltage fault is required, a settable start delay
and trip time can be obtained by combining two stages. See
Figure 2.17-1. Both the stages detect the overvoltage, but the
start signals are ignored. The trip signal of stage U> is used as
an alarm signal, and the trip information from stage U>> is
used for the actual trip. The overvoltage setting value for stage
U>> has to be higher than the setting value for stage U> to
ensure an alarm before trip.