Siemens SIPROTEC 4 7SJ61 Manual page 175

Operating Mode, Measured Quantity, Measurement Method
The flexible function can be tailored to assume a specific protective function for a concrete application in
parameters 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 oder no refer-
ence, i.e. without a fixed phase reference. The three-phase method evaluates all three phases in parallel. This
implies that threshold 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 protection. When operating single-phase, the function employs either a phase's measured quan-
tity, which must be stated explicitly, (e.g. evaluating only the current in phase Ib), or the measured ground
current In.
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 whether the function uses the r.m.s. value of the fundamental component or the normal r.m.s.
value (true RMS) that evaluates also harmonics. Parameter PICKUP WITH moreover specifies whether the
function picks up on exceeding 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 time delay is not affected by
the measured quantity.
Function Logic
The following figure 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.
SIPROTEC 4, 7SJ61, Manual
C53000-G1140-C210-6, Edition 05.2016
Functions
2.13 Flexible Protection Functions
175