Setting Notes - Siemens siprotec SJ62 User Manual

2.7.3

Setting Notes

General
Definite Time Ele-
ments
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
The settable dropout times do not affect the trip times of the inverse time elements
since they depend dynamically on the measured current value. Disk emulation is
applied here to coordinate the dropout behavior with the electromechanical relays.
Negative sequence protection 46 is configured at address 140, (see Section 2.1.1.2).
If only the definite time elements are desired, address 46 should be set to Definite
Time. Selecting 46 = TOC IEC or = TOC ANSI in address 140 will additionally make
all the parameters relevant for inverse characteristics available. If the function is not
required 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 appli-
cations. If data is available from the manufacturer regarding the permissable conti-
nous load imbalance and the permissable level of load imbalance per unit of time, then
this data should preferably be used. It is important to relate the manufacturer's data to
the primary values of the machine, for example, the maximum permissible continuous
inverse current related to the nominal machine current. For the settings on the protec-
tive relay, this information is converted to the secondary inverse current. The following
applies
with
I
2 perm prim
I
Nom Motor
I
CT sec
I
CT prim
The unbalanced load protection function is composed of two elements. Therefore, the
upper element (address 4004 46-2 PICKUP) can be set to a short time delay 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, a two-phase fault can be assumed. The
delay time 46-2 DELAY must be coordinated with the system grading of phase-to-
phase faults. If power supply with current I is provided via just two phases, the follow-
ing applies to the inverse current:
2.7 Negative Sequence Protection 46
Permissible Thermal Inverse Current of the Motor
Nominal Motor Current
Secondary Nominal Current of the Current Transform-
er
Primary Nominal Current of the Current Transformer
150