Determination Of Direction - Siemens siprotec SJ62 User Manual

Settable Dropout
Times

2.12.3 Determination of Direction

Characteristics
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
and 51NsTIME DIAL). Additionally, a current element with logarithmic inverse char-
acteristic or logarithmic inverse characteristic with knee point is implemented. The
characteristics of these current elements can be configured. Each of these elements
may work directional or non-directional.
The pickup can be stabilized for ground fault protection with definite time curve by a
settable dropout time. This facility comes into use in systems where intermittent faults
occur. Combined with electromechanical relays, it allows different dropout responses
to be adjusted and a time grading of numerical and electromechanical relays to be im-
plemented.
When determining the sensitive ground fault direction it is not the current value that is
crucial, but that part of the current which is perpendicular to an adjustable directional
characteristic (axis of symmetry). As a prerequisite for determining the direction, the
displacement voltage V
fluencing the direction (active or reactive component).
The following figure illustrates an example using a complex vector diagram in which
the displacement voltage V
part 3I0 of current 3I
real
compared with the setting value RELEASE DIRECT.. The example is therefore suited
for determining the ground fault direction in grounded systems where 3I
evant. The directional limit lines are perpendicular to axis 3I0
Figure 2-68 Directional characteristic for cos–ϕ–measurement
The directional limit lines may be rotated by a correction angle (address PHI
CORRECTION) up to ± 45°. Therefore, in grounded systems it is possible, e.g. to in-
crease sensitivity in the resistive-inductive range with a rotation of –45°, or in case of
electric machines in busbar connection in the resistive-capacitive range with a rotation
of +45° (see the following Figure). Furthermore the directional limit lines may be
rotated by 90° to determine ground faults and their direction in isolated systems.
2.12 Ground Fault Protection 64, 67N(s), 50N(s), 51N(s)
must be exceeded as well as a configurable current part in-
0
is the reference magnitude of the real axis. The active
0
is calculated in reference to the displacement voltage V
0
and
0
· cos ϕ is rel-
0
.
real
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