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SIPROTEC 7SJ81/7SK81 V4.70, Product Information
E50417-K1150-C462-A2, Edition 02.2012
The LPCT can have a nominal burden higher than the input impedance of
the connected protection devices, e.g. if several devices are connected to
the LPCT. This results in a linear amplitude distortion of the measured
current. Given the shunt resistance of the LPCT, the distortion can be
calculated. The correction factor parameters
320A
IL1 Corr.factor
,
321A
IL2 Corr.factor
,
322A
IL3 Corr.factor
,
323A
Corr.factor IE
und
324A
Corr.factor IEE
allow compensating
the distortion.
Rated Value of the Primary Object
With the parameter
310
Iph-PRIM ref.
, you can set the rated current
of the primary object. (This is equivalent to parameter 204
CT PRIMARY
for the 7SJ80).
With the parameter
312
Ignd-PRIM ref.
, you can set the reference
rated ground current of the object. (This is equivalent to parameter
217
Ignd-CT PRIM
for the 7SJ80).
Additional Parameters
With parameter
132
Earth CT
, you can set the measuring mode of the
device for ground currents in the menu “Device“. If you want to measure
small ground currents using a sensitive low-power current transformer,
use the
sensitive
setting. If you want to measure large ground currents
using a normal low-power current transformer, use the
normal
setting.
With parameter
252
Ph LPCT pol.
, you can set the polarity of the LPCT
currents.
If the parameters settings of the LPCT current measuring inputs are
invalid and impair the protection functionality, the indications 232
CT ph
mismatch
or 233
CT gnd mismatch
are output.
