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SIPROTEC 7SJ81/7SK81 V4.70, Product Information
E50417-K1150-C462-A2, Edition 02.2012
Due to the use of low-power current transformers, no physical current sum
can be formed. Therefore the Holmgreen connection and with it the fast
current sum monitoring or for example, the high-impedance ground-fault
differential protection is not possible.
Ratio of the Low-Power Current Transformers
The 7SJ81/7SK81
is equipped with 4 current measuring inputs for low-
power current transformers. The parameters
311
Iph-LPCT
PRIM
and
314
Uph-LPCT SEC
allow you to set the transformation ratio of the low-
power current transformers for the 3 phases of the device.
With the parameters
313
Ignd-LPCT PRIM
and
315
Ugnd-LPCT SEC
,
you can set the transformation ratio of an optional low-power current
transformer for the ground current input.
An LPCT with a secondary voltage
U-LPCT
SEC
higher than 1000 mV can
be parameterized by applying a linear transformation to the conversion
ratio.
Example: For split core LPCT with a conversion ratio 60 A : 7000 mV, the
parameters can be set as follows:
313
Ignd-LPCT PRIM
= 6 A
315
Ugnd-LPCT SEC
= 700 mV
Package
Function
7SJ81 7SK81
Additional
functionality
67 Directional overcurrent protection phase 67-1,
67-2, 67-3
X
67N Directional overcurrent protection ground
67N-1, 67N-2, 67N-3
X
X
67N(s)1 Directional sensitive ground fault protec-
tion 67N(s)-1, 67N(s)-2, 67N(s)-3
X
X
59N Displacement voltage
X
X
27/59 Under/Overvoltage
X
X
81 U/O Under/Overfrequency, f<, f>
X
X
47 Phase rotation
X
X
32/55/81R Flexible protection functions (current
and voltage parameters), Protective function for
voltage, power, power factor, frequency change
X
X
Additional
functions
Automatic Reclosing (AR)
X
Fault Locator (FL)
X
