Siemens 6MD85, Manual

Page: 721 / 1256

Table 7-7 Threshold Setting Range
Connection Type of the
Measuring Point I-3ph Ground Current CT Terminal Type Threshold Setting Range
(Secondary)
3-phase Calculated 4 * Protection 0.030 A to 35.000 A
3 * Protection, 1* sensitive 0.030 A to 35.000 A
4 * Measurement 0.001 A to 1.600 A
x + IN
x + IN-separate Measured 4 * Protection 0.030 A to 35.000 A
3 * Protection, 1* sensitive 0.001 A to 1.600 A
4 * Measurement 0.001 A to 1.600 A
Method of Measurement (Basic and Advanced Stage)
You use the
Method of measurement
parameter to define whether the stage uses the
fundamental
comp.
(standard method) or the calculated
RMS value
.
•
Measurement of the fundamental component:
This measuring procedure processes the sampled current values and filters out the fundamental compo-
nents numerically.
•
Measurement of the RMS value:
This measuring procedure determines the current amplitude from the sampled values according to the
defining equation of the RMS value. Harmonics are included in the analysis.
Directional Mode (Basic and Advanced Stage)
You can use the
Directional mode
parameter to define whether the stage works in a forward or reverse
direction.
The direction determination works across all stages (see chapter
7.7.3.2 Direction Determination ).
Pickup and Dropout Behaviors of the Inverse-Time Characteristic Curve According to IEC and ANSI (Basic and
Advanced Stage)
When the input variable exceeds the threshold value by a factor of 1.1, the inverse-time characteristic curve is
processed. An integrated measuring procedure totalizes the weighted time. The weighted time results from
the characteristic curve. For this, the time that is associated with the present current value is determined from
the characteristic curve. Once the weighted time exceeds the value 1, the stage operates.
When the measured value falls below the threshold value by a factor of 1.045 (0.95 × 1.1× threshold value),
the dropout starts. The pickup will be indicated as clearing. You can influence the dropout behavior via adjust-
able parameters. You can select between instantaneous dropout (totalized time is deleted) or dropout
according to the characteristic curve (reduction of totalized time depending on the characteristic curve). The
dropout according to characteristic curve (disk emulation) is the same as turning back a rotor disk. The
weighted reduction of the time is started from 0.9 of the set threshold value.
The characteristic curve and associated formulas are shown in the Technical data.
Minimum Time of the Curve (Advanced Stage)
With the parameter
Min. time of the curve
, you define a minimum operate delay time. The operate
delay time of inverse-time characteristic curve never falls below the minimum operate delay time.
Protection and Automation Functions
7.7 Directional Overcurrent Protection, Ground
SIPROTEC 5, High-Voltage Bay Controller, Manual 721
C53000-G5040-C015-9, Edition 11.2017