Siemens SIPROTEC 7SD80 Manual page 184

Functions
2.15 Flexible Protection Functions
The maximum 20 configurable protection functions operate independently of each other. The following descrip-
tion concerns one function; it can be applied accordingly to all other flexible functions. The logic diagram 2-77
illustrates the description.
Functional Logic
The function can be switched ON and OFF or, it can be set to Alarm Only. In this status, a pickup condition
will neither initiate fault recording nor start the trip time delay. Tripping is thus not possible.
Changing the Power System Data 1 after flexible functions have been configured may cause these functions
to be set incorrectly. Message (FNo.235.2128 „$00 inval.set") reports this condition. The function is in-
active in this case and function's setting has to be modified.
Blocking Functions
The function can be blocked via binary input (FNo. 235.2110 „>BLOCK $00") or on-site control („Control" ->
„Tagging" -> „Set"). When blocked, the entire measuring element of the function and all running times and in-
dications are reset. Blocking via on-site control can be important if the function is in a permanent pickup con-
dition and reparameterizing it is therefore not possible. For characteristics based on voltages it is possible to
block the function should a measuring voltage fail. The corresponding detection is accomplished via the internal
device function „Measuring-voltage failure detection" (FNo. 170 „VT FuseFail"; see Section 2.14.1). This
blocking mechanism can be enabled or disabled via parameters. The corresponding parameter BLK.by
Vol.Loss is only available if the characteristic is based on a voltage measurement.
When configuring the function as line protection or power supervision, the blocking will be effective for currents
below 0.03 I .
N
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 . 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 mea-
sured 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 fundamental
component. 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.
Functional 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.
184
SIPROTEC, 7SD80, Manual
E50417-G1140-C474-A1, Release date 09.2011