Functions
2.15 Flexible Protection Functions
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011
188
Table 2-8 Parameter in the "Measurement Method" settings dialog, 3-phase operation
Note
We see a special behavior of the phase-selective pickup indications for the 3-phase voltage protection with
phase-to-phase quantities, as the phase-selective pickup indication "Flx01 Pickup Lx" is assigned to the corre-
sponding measured value channel "Lx".
Operating
Method
Measurand Notes
3-phase Current,
voltage
Parameter MEAS.
METHOD
Setting selection
Fundamental component The fundamental component is evaluated, harmonics are sup-
pressed. This is the standard measurement method of the pro-
tection functions.
Important: The voltage threshold is always parameterized as
phase-to-phase voltage independently of parameter VOLTAGE
SYSTEM.
True RMS The "true" RMS value is determined, i.e. harmonics are evalu-
ated. This method is used, for instance, if a simple overload
protection on the basis of current measurement is to be imple-
mented, since harmonics contribute to thermal heating.
Important: The voltage threshold is always parameterized as
phase-to-phase voltage independently of parameter VOLTAGE
SYSTEM.
Positive-sequence
system,
negative-sequence
system,
zero-sequence system
To implement certain applications, the positive-sequence
system or the negative-sequence system can be parameterized
as measurement method. Examples are:
- I2 (unbalanced load protection)
- V2 (voltage unbalance)
When selecting the zero-sequence system, additional zero
current or zero voltage functions can be implemented that work
independently of the ground quantities IN and VN measured di-
rectly through transformers.
Important: The voltage threshold is always parameterized ac-
cording to the definition of the balanced components indepen-
dently of parameter VOLTAGE SYSTEM.
Current Ratio I2/I1 The ratio of the negative-sequence current to the positive-se-
quence current is evaluated.
Voltage Parameter VOLTAGE
SYSTEM
Setting selection
Phase-to-phase
Phase-to-ground
You can select whether a 3-phase voltage function is to evalu-
ate the phase-to-ground or the phase-to-phase voltage. When
selecting phase-to-phase, these quantities are calculated from
the phase-to-ground voltages. The selection is important, e.g.,
for 1-phase faults. If the faulted voltage collapses to zero, the
affected phase-to-ground voltage is zero, whereas the affected
phase-to-phase voltages collapse to the magnitude of a phase-
to-ground voltage.
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