Functions
2.17 Flexible Protection Functions
SIPROTEC, 7SJ62/64, Manual
C53000-G1140-C207-2, Release date 01.2008
285
Function 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 via local operating terminal
(„Control“ -> „Tagging“ -> „Set“). Blocking will reset the function's entire measurement logic as well as all
running times and indications. Blocking via the local operating terminal may be useful if the function is in a
status of permanent pickup which does not allow the function to be reset. In context with voltage-based char-
acteristics, the function can be blocked if one of the measuring voltages fails. Recognition of this status is either
accomplished by the relay's internal „Fuse-Failure-Monitor“ (FNo. 170
„VT FuseFail“
; see chapter 2.11.1)
or via auxiliary contacts of the voltage transformer CB (FNo. 6509
„>FAIL:FEEDER VT“
and FNo. 6510
„>FAIL: BUS VT“
). This blocking mechanism can be enabled or disabled in the according parameters. The
associated parameter
BLK.by Vol.Loss
is only available if the characteristic is based on a voltage measure-
ment.
When using the flexible function for power protection or power monitoring, it will be blocked if currents fall below
0.03
I
Nom
.
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.
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