Siemens siprotec 7SA6 User Manual

Functions
6-130 7SA6 Manual
C53000-G1176-C156-2
For the inverse time overcurrent stage 3I
0P
it is possible to select from a variety of
curves depending on the version of the relay and the configuration (Section 5.1, ad-
dress
131) that was selected. If an inverse overcurrent stage is not required, the ad-
dress
131 is set to Earth Fault O/C = Definite Time. The 3I
0P
–stage can then
be used as a fourth definite time stage (refer to “Definite Time Stages” above) or de-
activated. In the case of the ANSI–curves (address
131 Earth Fault O/C = TOC
ANSI
) the following alternatives are available in the address 3151 ANSI Curve:
Inverse,
Short inverse,
Long inverse,
Moderately inv.,
Very inverse,
Extremely inv. and
Definite inv.
The curves and equations the curves are based on are illustrated in the technical data
(Section 10.5, Figure 10-1 and 10-3).
The setting of the pick-up threshold
3I0p PICKUP (address 3141) is similar to the
setting of definite time stages (see above). In this case it must be considered that a
safety margin has already been included between the pick-up threshold and the set-
ting value. The stage only picks up when the measured signal is approximately 10 %
above the setting value.
The time multiplier setting
3I0p Time Dial (address 3144) is derived from the grad-
ing coordination chart which was set up for earth faults in the system.
In addition to the inverse current dependant time delay, a constant (fixed length) time
delay can also be set if this is required. The setting
Add.T-DELAY (address 3147)is
addedtothetimeofthesetcurve.
Inverse Time
Overcurrent Stage
with Logarithmic–
Inverse
Characteristic
For the inverse time overcurrent stage with logarithmic inverse characteristic the op-
erating mode is initially set:
Op. mode 3I0p (address 3140). This stage can be set
to operate
Forward (usually towards line) or Reverse direction (usually towards bus-
bar) or
Non-Directional (in both directions). If this stage is not required, set its
mode to
Inactive.
For the inverse logarithmic curves (address
131 Earth Fault O/C = TOC Loga-
rithm.
) the following can be set: address 3153 LOG Curve = Log. inverse.
The curves and equations the curves are based on are illustrated in the technical data
(Section 10.5, Figure 10-4). Figure 6-75 illustrates the influence of the most important
setting parameters on the curve.
3I0p PICKUP (address 3141) is the reference value
for all current values, while
3I0p Startpoint (address 3154) determines the be-
ginning of the curve, i.e. the lowest operating range on the current axis (referred to
3I0p PICKUP). The timer setting 3I0p MaxT-DELAY (address 3146) determines
the starting point of the curve (for 3
I
0
= 3I0p PICKUP). The time factor 3I0p Time
Dial
(address 3145) changes the slope of the curve. For large currents, 3I0p
MinT-DELAY
(address 3142) determines the lower limit on the time axis. For currents
larger than 30·
3I0p PICKUP the operating time no longer decreases.
Finally in address
3147 Add.T-DELAY a fixed time delay can be set as was done for
other curves. This, however, has almost the same effect on the characteristic as an
increase of
3I0p MaxT-DELAY (address 3146), but no effect on 3I0p MinT-DELAY
(address 3142).

Siemens siprotec 7SA6 Specifications

General

Brand	Siemens
Model	siprotec 7SA6
Category	Relays
Language	English