Siemens SENTRON 3WL10 - Page 60

With open contacts, too, signals can be provided if the voltage is sensed on the line side
to detect anomalies or faults in the voltage applied before the main contacts of the circuit
breaker are closed.
Reverse active power protection: Reverse power protection (RP)
If the power 󹪞ows through the device in the opposite direction to the direction of power
󹪞ow de󹪝ned as 'normal,' the reverse power protection RP detects this and can trip the circuit
breaker when an operating value for the active power is exceeded. The user can freely de󹪝ne
the direction of power 󹪞ow in the parameters.
For reverse power protection RP, the direction of the power 󹪞ow is determined continuously
in the ETU based on the power factor (PF) by evaluation of the current and voltage signal and
the active and apparent power are placed in relation to each other. Based on the sign of the
PF or the phase displacement angleφ between the current and voltage signal, deviating or
reversing power 󹪞ows are identi󹪝ed. Besides the RP protection function, the DST protection
function is also a typical application for this.
Power factor PF
avg
- alarm
A warning signal can also be transmitted as soon as a de󹪝ned deviation of the averaged
power factor PF
avg
of the 3-phase system of <1 is reached, i.e. increasing generation of
reactive power and an undesired large phase di󹪜erence between the current and voltage.
Corrective action can be derived from this (e.g. reactive power compensation).
DST - directed short-time protection
Directed (directional) short-time protectionDST behaves like short-time-delayed short-circuit
protection(ST) except that the tripping current and the delay time depend on the direction
of power 󹪞ow. The user can de󹪝ne which direction is the forward direction. Based on this, it
is possible to de󹪝ne individually the current operating values and time delays in this forward
direction (FW) and in the backward direction (BW). This ensures di󹪜erently selective behavior
of the device depending on the direction of power 󹪞ow.
Voltage unbalance V-NBA
The voltage unbalance protection function provides protection from unwanted unbalance of
the voltage between the phases and load unbalances in the distribution and at the load. It
can open the circuit breaker with a constant, de󹪝nable delay time t
nba(U)
if a phase-to-phase
voltage (U
ph
-U
ph
) deviates by more than the set operating value U
nba
from the arithmetic
mean of the phase-to-phase voltages. The deviation of the operating value from the mean
value is stated as a percentage [%].
Underfrequency protection (f
u
)
Underfrequency protection responds with a de󹪝nable de󹪝nite-time delay t
u
(f) as soon as the
line frequency falls below the operating valuef
u
.
The operating value is described as factor <1 of the line frequency - settable to 50Hz or
60Hz.
In this way, the distribution board can be protected from impermissible deviations in the line
frequency.
Overfrequency protection (f
o
)
Overfrequency protection responds with a de󹪝nable de󹪝nite-time delay t
o
(f) as soon as the
line frequency exceeds the operating valuef
o
.
Description
2.9Electronic trip unit ETU
3VA27 molded case circuit breakers & 3WL10 air circuit breakers
Equipment Manual, 10/2023, L1V30499596002-03 59