Siemens SIPROTEC 7SS522 V4.6, Руководство пользователя

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Functions
190
7SS52 V4 Manual
C53000-G1176-C182-3
Definite-time over-
current protection For the overcurrent stage and/or the high-set current stage, thresholds for the phase
current can be set with the parameters
I>
(
1212/BU
) or
I>>
(
1202/BU
) respectively
Each phase current is compared individually with these thresholds, and a phase-se-
lective signal is issued if these thresholds are exceeded. After the corresponding delay
times
TI>
(
1213/BU
) or
TI>>
(
1203/BU
) respectively have elapsed, the TRIP com-
mand is issued. The TRIP command is available individually for the overcurrent and
for the high-set stage.
For the earth fault stages, the thresholds for the phase currents are set with the pa-
rameters
IE>
(
1512/BU
) or
IE>>
(
1502/BU
) respectively. The earth fault is com-
pared with the thresholds. As soon as one of these thresholds is exceeded, the delay
time
TIE>
(
1513/BU
) or
TIE>>
(
1503/BU
) respectively is started. After this delay
has elapsed, a TRIP command is issued.
Inverse-time
overcurrent protec-
tion For the overcurrent and the high-set stage, thresholds for the phase current can be set
with the parameters
Ip
(
1214/BU
) or
I>>
(
1202/BU
) respectively. Each phase cur-
rent is compared individually with these thresholds. For both stages, the thresholds for
the earth current can be set with the parameters
IEp
(
1514/BU
) or
IE>>
(
1502/BU
)
respectively. The earth fault is compared with the thresholds. If the Ip or the IEp
threshold is exceeded, the time to trip is calculated and started. The time to trip is cal-
culated on the basis of the flowing fault current, and depends on the selected trip time
multiplier. The time multiplier is set with the parameters
TIp
(
1215/BU
) or.
TIEp
(
1515/BU
) respectively.
If the thresholds for the high-set stage of the phase or earth current are exceeded, a
TRIP command is always issued as soon as the current-independent trip time has
elapsed. This happens regardless of the tripping characteristic set for Ip and/or IEp.
In inverse-time overcurrent protection, the parameters
RMS FORMAT
(
1216/BU
) or
(
1516/BU
) respectively are used to specify whether the currents will be evaluated as
r.m.s. values, or on the basis of their fundamental wave obtained by means of digital
filtering.
5.16.2 Setting Notes
O/C PHASES
The parameter
O/C PHASES
(
1201/BU
)
is used to activate and deactivate the O/C
protection for the phase currents.
With setting
ON
, the O/C protection for the phase currents is active.
With setting
OFF
, the O/C protection for the phase currents is deactivated.
I>>
In a first step, the high-set stage
I>>
is set (
1202/BU
to
1206/BU
). This stage is of-
ten used for current grading before high impedances such as transformers, motors or
generators. The high-set current stage
I>> is always a definite time stage, regardless
of the tripping characteristic set for the I> stage. It is set such that it picks up on short-
circuits into this impedance.
All set times are pure delay times which do not include the operating times of the pro-
tection (measuring time, dropout time). If the
I>> stage is not required, the time
TI>>
(
1203/BU
)
is set to infinite.
The parameter
I>>
(
1202/BU
)
is used to the threshold for the phase currents in the
high-set stage (definite-time).
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