6.3.1
Identification
SEMOD158971-2 v5
Function description
IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Generator differential protection
GENPDIF
I
d
>
SYMBOL-NN V1 EN-US
87G
6.3.2
Functionality
SEMOD143239-4 v10
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 (87G) is also well suited for protection of shunt
reactors or small busduct.
1MRK 502 066-UUS B
Section 6
Differential protection
149
Technical manual
Содержание Relion 670 series
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