Siemens 6MD85 - Application and Setting Notes

Pickup Mode
The Pickup mode parameter defines 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 overvoltage
condition (1 out of 3).
Measured Value
Use the Measured value parameter to define whether the tripping 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.
Blocking the Stage
In the event of blocking, the picked up stage will be reset. Blocking is possible externally or internally via the
binary input signal
>Block stage .
Application and Setting Notes
Parameter: Method of measurement
•
Recommended setting value (_:181:8) Method of measurement = fundamental comp.
With the Method of measurement parameter, you define whether the stage uses the fundamental
component (standard method = default setting) or the calculated RMS value.
Parameter Value
Description
fundamental comp.
Select this method of measurement to suppress harmonics or transient
voltage peaks.
Siemens recommends this method of measurement as the default setting.
RMS value
Select this method of measurement if you want the stage to take harmonics
into account (for example, at capacitor banks). Do not set the threshold
value of the stage under 10 V for this method of measurement.
Parameter: Measured value
•
Default setting (_:181:9) Measured value = phase-to-phase
With the Measured value parameter, you define whether the stage monitors 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
.
Parameter Value
Description
phase-to-phase
If you want to monitor the voltage range, keep phase-to-phase as the
default setting. In this case, the function will not pick up on ground faults.
Siemens recommends the measured value phase-to-phase as the
default setting.
phase-to-ground
Select the phase-to-ground setting if you want to detect voltage unbal-
ances and overvoltage conditions caused by ground faults.
Parameter: Threshold
•
Default setting (_:181:3) Threshold = 110 V
Depending on the Measured value , the Threshold is set either as phase-to-phase quantity or as phase-
to-ground quantity. The default setting assumes that the voltage range is monitored on long-distance trans-
mission lines under low-load conditions.
Specify the Threshold (pickup threshold) for the specific application.
7.13.4
Protection and Automation Functions
7.13 Overvoltage Protection with 3-Phase Voltage
SIPROTEC 5, High-Voltage Bay Controller, Manual 785
C53000-G5040-C015-9, Edition 11.2017