Siemens SIPROTEC 7SJ62 Instruction Manual page 221

Ungrounded
System
Grounded System
Electrical Motors
7SJ62 Manual
C53000-G1140-C121-1
− Address  = FRV
Ã
spect to the displacement voltage (the component of 3I
evaluated by the setting at address  (see Figure 6-32);
− Address  = VLQ ϕ: the reactive (capacitive) component of the zero sequence
current with respect to the displacement voltage (the component of 3I
by 90°) is evaluated by the setting at address  (see Figure 6-38).
V or 3V
0 0
U`Q@ÃPAÃH@6TVS@H@IU
0(66$57
3I
I
Forward
((E
3I reactive
0
(capacitive)
3+, .255(.7 85
QCDÃ8PSS@8UDPI
Directional Line for sin ϕ Measurement
Figure 6-38
The directional line, in this respect, may be rotated within the range ± 45° — as shown
in Figure 6-33.
In an ungrounded system, no zero sequence fault current exists, therefore, the zero
sequence charging current must be used for directional determination. As is the case
with the zero sequence fault current, the zero sequence charging current will also lead
the zero sequence voltage for a fault in the forward direction. A setting equal to about
half of this current should be selected at address . The measurement time se-
lected at address  should be VLQ
In a grounded system, address  should be set below the minimum anticipated
ground fault current. It is important to note that only the current components that are
perpendicular to the directional limit lines defined at addresses  and  will be
evaluated. &RV ϕ is the type of measurement used, and the correction angle is set to
–45 ° , since the ground fault current is typically resistive-inductive (right portion of Fig-
ure 6-33).
One may set the value cos ϕ for the measurement type and use a correction angle of
+45° for electrical motors supplied from a common bus in an ungrounded system,
since the ground connection current is often composed of an overlap of the capacitive
ground current from the system and the resistive current of the load resistance (Figure
6-33, left section).
ϕ: the real component of the zero sequence current with re-
TDIÃQCD
VLQ 3+,
=
real V
0 U 0
E Ew E
3I
0
I
EE
Inductive
IEE 3I
0
G E R
dir
Reverse
3I dir=
0
Set at Addr.
3123
ƒ

=
ϕ.
Ã
Functions
in phase with V or 3V
0 0 0
that leads
0
6-81
) is