Function Block - ABB Relion Technical Manual

Section 8
Current protection
8.9.3
266
To provide an effective protection for the generator for external unbalanced conditions,
NS2PTOC (46I2) is able to directly measure the negative sequence current. NS2PTOC
(46I2) also has a time delay characteristic which matches the heating characteristic of the
2
=
I t K
generator as defined in standard IEEE C50.13.
2
where:
I
2
t
K
NS2PTOC (46I2) has a wide range of K settings and the sensitivity and capability of
detecting and tripping for negative sequence currents down to the continuous capability of
a generator.
In order to match the heating characteristics of the generator a reset time parameter can be
set.
A separate definite time delayed output is available as an alarm feature to warn the
operator of a potentially dangerous situation.

Function block

NS2PTOC (46I2)
I3P* TRIP
BLOCK TRST1
BLK1 TRST2
BLK2 PICKUP
PU_ST1
PU_ST2
ALARM
NSCURR
ANSI08000359-2-en.vsd
ANSI08000359 V2 EN
Figure 121: NS2PTOC (46I2) function block
is negative sequence current expressed in per unit of the rated generator
current
is operating time in seconds
is a constant which depends of the generators size and design
1MRK 502 048-UUS A
Technical manual