Siemens 7SJ85 - Page 699

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Measurement RMS value :
This method of measurement determines the voltage amplitude from the sampled values according to
the defining equation of the RMS value. Harmonics are included in the analysis.
Pickup Mode
With the Pickup mode parameter, you define whether the protection stage picks up if all 3 measuring
elements detect the overvoltage condition ( 3 out of 3 ) or if only 1 measuring element detects the over-
voltage condition ( 1 out of 3 ).
Measured Value
Use the Measured value parameter to define whether the stage analyzes the phase-to-phase voltages V
AB
,
V
BC
, and V
CA
, or the phase-to-ground voltages V
A
, V
B
, and V
C
.
If the measured value is set to phase-to-phase, the function reports those measuring elements that have
picked up.
Pickup and Operate Curve
When the input voltage exceeds the threshold value by a settable value Pickup factor , the stage picks up
and the inverse-time characteristic curve is processed. Operate delay starts. The operate delay is the sum of
inverse-time delay and additional time delay.
Where
T
op
Operate delay
T
inv
Inverse-time delay
T
add
Additional time delay (parameter Additional time delay )
After pickup, the time value T
inv
is calculated for every input voltage that exceeds the threshold. An integrator
accumulates the value 1/T
inv
. Once the accumulated integral reaches the fixed value 1, the inverse-time delay
expires. The additional time delay T
add
starts. The stage operates after the additional time delay expires.
Protection and Automation Functions
6.23 Overvoltage Protection with 3-Phase Voltage
SIPROTEC 5, Overcurrent Protection, Manual 699
C53000-G5040-C017-8, Edition 07.2017