VAMP 135
Over-, under-, residual voltage and
frequency relay
Technical description
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VM135.EN008
2.2.3.
Protection configuration Line+U
0
SCALING/U
mode
: Line+ U
0
•
The relay is connected to the line voltages U
12
, U
23
and the
residual voltage U
0
, see Figure 3.3-1.
•
The setting values of the overvoltage and undervoltage
limits are relative to the rated line voltage U
N
(100% = U
N
).
U
N
= voltage transformers primary voltage VT
primary
which
is defined by the user in the configuration.
•
The setting values of the residual voltage limits are relative
to the rated residual voltage VT
0secondary
(100% = VT
0secondary
)
which is defined by the user.
2.3.
Relay protection functions
2.3.1.
Overvoltage protection U>, U>>, U>>> (59)
The three-phase overvoltage unit comprises three separately
adjustable overvoltage stages (stage U>, U>> and U>>>).
The overvoltage unit measures the fundamental frequency
component of the line voltages. The protection stages operate
with definite time characteristics.
The relay starts, if the actual value of any phase exceeds the
setting value. If the overvoltage situation continues after the
operation time has elapsed, the relay trips.
The overvoltage stages have a fixed start delay. If, however, a
delayed alarm about a voltage fault is required, a settable start
time and trip time can be obtained by combining two stages.
See Figure 2.3.1-2.
The U> stage has a settable release delay, which makes it
possible to detect intermittent faults. This means that the
protection unit’s time counter 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 delay counter continues from the previous value.
This means that the relay trips after a certain number of
intermittent faults.