Siemens siprotec SJ62 User Manual page 205

2 Functions
Method of Direc-
tional Measurement
203
Figure 2-69 Directional characteristic for cos–ϕ–measurement
Fault direction is calculated with the zero sequence values from the ground current 3I
and displacement voltage V
ground reactive power is calculated.
The used calculation algorithm filters the measured values so that it is highly accurate
and insensitive to higher harmonics (particularly the 3rd and 5th harmonics – which
are often present in zero sequence currents). Direction determination relies on the
sign of active and reactive power.
Since active and reactive components of the current - not the power - are relevant for
pickup, current components are calculated from the power components. When deter-
mining the ground fault direction the active or reactive components of the ground
current in reference to the displacement voltage as well as the direction of the active
and reactive power are evaluated.
For measurements sin ϕ the following applies
• Ground fault (forward direction), if Q
DIRECT.),
• Ground fault (reverse direction), if Q
DIRECT.).
For measurements cos ϕ (for resonant-grounded systems) the following applies
• Ground fault (forward direction), if P
DIRECT.),
• Ground fault (reverse direction), if P
DIRECT.).
If PHI CORRECTION unequal 0°, the angle of the symmetrie lines is calculated by
adding up active and reactive power components.
or 3 · V . With these quantities, ground active power and
0 0
< 0 and 3I0
0
> 0 and 3I0
0
> 0 and 3I0
0
< 0 and 3I0
0
> setting value (RELEASE
reactive
> setting value (RELEASE
reactive
> setting value (RELEASE
reactive
> setting value (RELEASE
reactive
SIPROTEC 4, 7SJ62/63/64 Handbuch
C53000-G1140-C147-A, Edition 07.2015
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