ABB Relion REG670, Техническое руководство

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6.3.6 Monitored data
Table 59: GENPDIF Monitored data
Name Type Values (Range) Unit Description
IDL1MAG REAL - A Fund. freq. differential
current, phase L1; in
primary A
IDL2MAG REAL - A Fund. freq. differential
current, phase L2; in
primary A
IDL3MAG REAL - A Fund. freq. differential
current, phase L3; in
primary A
IDNSMAG REAL - A Negative Sequence
Differential current; in
primary Amperes
IBIAS REAL - A Magnitude of the
common Bias current; in
primary Amperes
6.3.7 Operation principle
The task of Generator differential protection GENPDIF is to determine whether a fault
is within the protected zone, or outside the protected zone. The protected zone is
delimited by the position of current transformers, as shown in figure
48 .
IEC06000430-2-en.vsd
IEC06000430 V2 EN
Figure 48: Position of current transformers; the recommended (default)
orientation
If the fault is internal, the faulty generator must be quickly tripped, that is,
disconnected from the network, the field breaker tripped and the agent to the prime
mover interrupted.
GENPDIF function always uses reference (default) directions of CTs towards the
protected generator as shown in figure
48 . Thus, it always measures the currents on the
two sides of the generator with the same reference direction towards the generator
windings. With the orientation of CTs as in figure
48 , the difference of currents
flowing in, and out, of a separate stator winding phase is simply obtained by
summation of the two currents fed to the differential protection function.
Numerical IEDs have brought a large number of advantages and new functionality to
the protective relaying. One of the benefits is the simplicity and accuracy of
calculating symmetrical components from individual phase quantities. Within the
firmware of a numerical IED, it is no more difficult to calculate negative-sequence
Section 6
1MRK502052-UEN B
Differential protection
150
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