Setting Notes - Siemens SIPROTEC 7SJ61 Manual

Functions
2.5 Negative Sequence Protection 46
2.5.3

Setting Notes

General
The function type has been specified during configuration of the protection functions (Section 2.1.1.2, address
140 46). If only the definite time elements are desired, the address 46 should be set to Definite Time. Se-
lecting 46 = TOC IEC or TOC ANSI in address 140 will additionally make all parameters available that are
relevant for the inverse time curves. If this function is not required, then Disabled is set.
The function can be turned ON or OFF in address 4001 FCT 46.
The default pickup settings and delay settings are generally sufficient for most applications. If data is available
from the manufacturer regarding the allowable long-term load imbalance and the allowable load imbalance per
unit of time, this data should be used preferentially. It is important to note that the manufacturer's data relate to
the primary values of the machine, for example, the maximum permissible permanent inverse current is re-
ferred to the nominal machine current. For the setting values at the protection device, this information is con-
verted to the secondary inverse current. The following applies
with
I
2 perm prim
I
Nom Motor
I
CT sec
I
CT prim
Definite Time Elements
The unbalanced load protection function comprises elements. Therefore, the upper element (address 4004
46-2 PICKUP) can be set to a short time delay (address 4005 46-2 DELAY) and the lower element (address
4002 46-1 PICKUP) can be set to a somewhat longer time delay (address 4003 46-1 DELAY). This allows
the lower element to act, e.g. as an alarm, while the upper element will cut the inverse characteristic as soon
as high inverse currents are present. If 46-2 PICKUP is set to about 60%, tripping is always performed with
the thermal characteristic. On the other hand, with more than 60 % of unbalanced load the user will assume a
phase-to-phase fault. The delay time 46-2 DELAY must be coordinated with the system grading for phase-to-
phase faults. If power supply with current I is provided via just two phases, the following applies to the inverse
current:
98
permissible thermal inverse current of the motor
Nominal Motor Current
Secondary Nominal Current of the Current Transformer
Primary nominal current of the current transformer
SIPROTEC, 7SJ61, Manual
C53000-G1140-C210-1, Release date 02.2008