Sensitive Directional Residual Overcurrent And Power Protection Sdepsde (67N) - ABB REL650 Applications Manual

Section 7
Current protection
7.7
7.7.1
7.7.2
214
Sensitive directional residual overcurrent and power
protection SDEPSDE (67N)
Identification
Function description
Sensitive directional residual over
current and power protection
Application
In networks with high impedance grounding, the phase-to-ground fault current is
significantly smaller than the short circuit currents. Another difficulty for ground-fault
protection is that the magnitude of the phase-to-ground fault current is almost independent
of the fault location in the network.
Directional residual current can be used to detect and give selective trip of phase-to-
ground faults in high impedance grounded networks. The protection uses the residual
current component 3I · cos φ, where φ is the angle between the residual current and the
0
residual voltage (-3V ), compensated with a characteristic angle. Alternatively, the
0
function can be set to strict 3I
Directional residual power can also be used to detect and give selective trip of phase-to-
ground faults in high impedance grounded networks. The protection uses the residual
power component 3I · 3V
0
the reference residual voltage, compensated with a characteristic angle.
A normal non-directional residual current function can also be used with definite or
inverse time delay.
A back-up neutral point voltage function is also available for non-directional sensitive
back-up protection.
In an isolated network, that is, the network is only coupled to ground via the capacitances
between the phase conductors and ground, the residual current always has -90º phase shift
compared to the reference residual voltage. The characteristic angle is chosen to -90º in
such a network.
In resistance grounded networks or in Petersen coil grounded, with a parallel resistor, the
active residual current component (in phase with the residual voltage) should be used for
the ground-fault detection. In such networks the characteristic angle is chosen to 0º.
IEC 61850
identification
SDEPSDE
level with a check of angle 3I
0
· cos φ, where φ is the angle between the residual current and
0
1MRK 506 334-UUS A
IEC 60617 ANSI/IEEE C37.2
identification device number
- 67N
and cos φ.
0
Application manual