Functions
2.13 Flexible Protection Functions
SIPROTEC, 7SK80, Manual
E50417-G1140-C344-A4, Release date 08.2010
207
Operating Mode, Measured Quantity, Measurement Method
The flexible function can be tailored to assume a specific protective function for a concrete application in pa-
rameters OPERRAT. MODE, MEAS. QUANTITY, MEAS. METHOD and PICKUP WITH. Parameter OPERRAT.
MODE can be set to specify whether the function works 3-phase, 1-phase or no reference, i.e. without a
fixed phase reference. The three-phase method evaluates all three phases in parallel. This implies that thresh-
old evaluation, pickup indications and trip time delay are accomplished selectively for each phase and parallel
to each other. This may be for example the typical operating principle of a three-phase time overcurrent pro-
tection. When operating single-phase, the function employs either a phase's measured quantity, which must be
stated explicitly, (e.g. evaluating only the current in phase Ib), the measured ground current In or the mea-
sured displacement voltage Vn. If the characteristic relates to the frequency or if external trip commands are
used, the operating principle is without (fixed) phase reference. Additional parameters can be set to specify
the used MEAS. QUANTITY and the MEAS. METHOD. The MEAS. METHOD determines for current and voltage
measured values whether the function uses the rms value of the fundamental component or the normal r.m.s.
value (true RMS) that evaluates also harmonics. All other characteristics use always the rms value of the fun-
damental component. Parameter PICKUP WITH moreover specifies whether the function picks up on exceed-
ing the threshold (>-Element) or on falling below the threshold (<-Element).
Characteristic Curve
The function's characteristic curve is always „definite time“; this means that the delay time is not affected by the
measured quantity.
Function Logic
Figure 2-77 shows the logic diagram of a three-phase function. If the function operates on one phase or without
phase reference, phase selectivity and phase-specific indications are not relevant.
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