Siemens 6MD86 - Page 790

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.
The inverse-time characteristic is shown in the following figure.
[dwovpinv, 2, en_US]
Figure 7-143
Operate Curve of Inverse-Time Characteristic
The inverse-time delay is calculated with the following formula:
Protection and Automation Functions
7.13 Overvoltage Protection with 3-Phase Voltage
790 SIPROTEC 5, High-Voltage Bay Controller, Manual
C53000-G5040-C015-9, Edition 11.2017