Identification - ABB REG670 Applications Manual

1MRK 502 071-UEN -
9.6.1
9.6.2
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062
Application manual

Identification

Function description
Sensitive directional residual over
current and power protection
Application
In networks with high impedance earthing, the phase-to-earth fault current is
significantly smaller than the short circuit currents. Another difficulty for earth fault
protection is that the magnitude of the phase-to-earth 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-
earth faults in high impedance earthed networks. The protection uses the residual
current component 3I · cos φ, where φ is the angle between the residual current and
0
the residual voltage (-3U
the function can be set to strict 3I
Directional residual power can also be used to detect and give selective trip of phase-
to-earth faults in high impedance earthed networks. The protection uses the residual
power component 3I · 3U
0
and 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 backup neutral point voltage function is also available for non-directional residual
overvoltage protection.
In an isolated network, that is, the network is only coupled to earth via the capacitances
between the phase conductors and earth, the residual current always has -90º phase
shift compared to the residual voltage (3U
in such a network.
In resistance earthed networks or in Petersen coil earthed, with a parallel resistor, the
active residual current component (in phase with the residual voltage) should be used
for the earth fault detection. In such networks, the characteristic angle is chosen to 0º.
As the amplitude of the residual current is independent of the fault location, the
selectivity of the earth fault protection is achieved by time selectivity.
When should the sensitive directional residual overcurrent protection be used and
when should the sensitive directional residual power protection be used? Consider the
following:
• Sensitive directional residual overcurrent protection gives possibility for better
sensitivity. The setting possibilities of this function are down to 0.25 % of IBase,
IEC 61850
identification
SDEPSDE
), compensated with a characteristic angle. Alternatively,
0
level with a check of angle φ.
0
· cos φ, where φ is the angle between the residual current
0
). The characteristic angle is chosen to -90º
0
Section 9
Current protection
IEC 60617 ANSI/IEEE C37.2
identification device number
- 67N
357