VAMP Ltd
Over-, under-, residual voltage and
frequency relay
Technical description
VAMP 135
VM135.EN008
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11
The relay starts, if the actual value of any phase exceeds the
setting value. If the undervoltage situation continues after the
start time has elapsed, the relay trips.
The undervoltage stage U< 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 trip counter continues from the previous fault
value. This means that the relay trips after a certain number of
intermittent faults.
The undervoltage unit can be blocked with an external digital
signal, for example if the secondary voltage of the measuring
transformers disappears. The undervoltage unit can also be
blocked with an internal blocking signal, which is defined
during parametrization. Further the unit can be blocked with a
separate NoCmp setting. With this setting all protection stages
are blocked when actual values for all phases falls below the set
value.
Figure 2.3.2-1. Block diagram of the three-phase undervoltage stages U<,
U<< and U<<<
Parameters of the undervoltage stages:
U<, U<<, U<<< (27)
U<, U<<, U<<< (27)
U<, U<<, U<<< (27)
U<, U<<, U<<< (27)
Parameter
Parameter
Parameter
Parameter
Value/unit
Value/unit
Value/unit
Value/unit
Measured
value
U<, U<<,
U<<<
V
Max. value of line voltages U
12
to U
31
primary values
U<, U<<,
U<<<
%
Setting value in relation to the
rated voltage U
n
t<, t<<,
t<<<
s
Operation time
NoCmp
%
Self-blocking value in relation
to the rated voltage Un
ReleaseDly
s
Release delay [s] (only U<)
Setting
values
Hysteresis
%
Deadband (only U<)
SCntr
Start counter (Start) reading
Recorded
values
TCntr
Trip counter (Trip) reading
