Generator Differential Protection Genpdif - ABB REG670 Technical Manual

Section 6
Differential protection
6.3
6.3.1
6.3.2
146

Generator differential protection GENPDIF

Identification
Function description
Generator differential protection
Functionality
Short circuit between the phases of the stator windings causes normally very large
fault currents. The short circuit gives risk of damages on insulation, windings and
stator iron core. The large short circuit currents cause large forces, which can cause
damage even to other components in the power plant, such as turbine and generator-
turbine shaft.
To limit the damage due to stator winding short circuits, the fault clearance must be as
fast as possible (instantaneous). If the generator block is connected to the power
system close to other generating blocks, the fast fault clearance is essential to maintain
the transient stability of the non-faulted generators.
Normally, the short circuit fault current is very large, that is, significantly larger than
the generator rated current. There is a risk that a short circuit can occur between phases
close to the neutral point of the generator, thus causing a relatively small fault current.
The fault current can also be limited due to low excitation of the generator. Therefore,
it is desired that the detection of generator phase-to-phase short circuits shall be
relatively sensitive, detecting small fault currents.
It is also of great importance that the generator differential protection does not trip for
external faults, with large fault currents flowing from the generator.
To combine fast fault clearance, as well as sensitivity and selectivity, the generator
differential protection is normally the best choice for phase-to-phase generator short
circuits.
Generator differential protection GENPDIF is also well suited for protection of shunt
reactors or small busduct.
IEC 61850 IEC 60617
identification identification
GENPDIF
I
d
SYMBOL-NN V1 EN
1MRK502052-UEN B
ANSI/IEEE C37.2
device number
87G
>
Technical manual