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Three-phase – functions evaluate the three-phase measuring system, i.e. all three phases are processed
simultaneously. A typical example is the three-phase operating time overcurrent protection.
Single-phase – functions evaluate only the individual measuring value. This can be an individual phase value
(e.g V
) or a ground variable (V
B
Setting no reference determines the evaluation of measured variables irrespective of a single or threep-
hase connection of current and voltage. Table 2-20 provides an overview regarding which variables can be
used in which mode of operation.
Measured Variable
In the setting dialog "Measured Variable" the measured variables to be evaluated by the flexible protection
functions can be selected, which may be a calculated or a directly measured variable. The setting options that
can be selected here are dependent on the mode of measured-value processing as predefined in parameter
OPERRAT. MODE (see the following table).
Table 2-7
Parameter OPERRAT. MODE
Setting
1-phase
3-phase
without reference
Measurement Methods
The measurement methods shown in the following tables can be parameterized for the measurands current,
voltage and power. Additionally, the dependencies of the available measurement methods on the parameter-
ized operating method and measurand are shown.
Table 2-8
Parameter OPERRAT. MODE = 3-phase
Parameter MEAS. QUANTITY = Current or Voltage
Parameter MEAS. METHOD
Fundamental
True RMS
SIPROTEC 4, 7SD80, Manual
E50417-G1100-C474-A2, Edition 02.2018
or Ι
).
N
N
Parameter "Operating method" and "Measured Quantity"
Parameter MEAS. QUANTITY
Setting selection
Current
Voltage
P forward
P reverse
Q forward
Q reverse
Power factor
Frequency
df/dt rising
df/dt falling
Binary Input
Parameter in the Setting Dialog "Measurement Procedure", Mode of Operation 3-phase
Only the fundamental harmonic is evaluated, higher harmonics are suppressed. This is
the standard measurement procedure of the protection functions.
Important: The voltage threshold value is always parameterized as phase-to-phase
voltage. If parameter VOLTAGE SYSTEM is selected as phase-to-ground, the voltage
threshold will be devided by √3.
The "true" RMS value is determined, i.e. higher harmonics are evaluated. This procedure is
applied, for example, if an overload protection element must be realized on the basis of a
current measurement, as the higher harmonics contribute to thermal heating.
Important: The voltage threshold value is always parameterized as phase-to-phase
voltage. If parameter VOLTAGE SYSTEM is selected as phase-to-ground, the voltage
threshold will be devided by √3.
Functions
2.15 Flexible Protection Functions
171
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