ABB REG670 - Page 168

Calculation
Idiff and Ibias
Calculation
instantaneous
Idiff
Start and
trip logic
TRIP
Signals
START
Signals
BLOCK
Signals
Intern/
extern
Fault
Phasors IL1N, IL2N,IL3N
Phasors IL1T, IL2T,IL3T
Samples IL1N, IL2N,IL3N
Samples IAT, IBT,ICT
Magnitude
Idiff and Ibias
Samples Idiff
Diff.prot.
characteristic
Hamonic
analysis: DC,
2nd and 5th
Start
phase
selective
Phasor IL1N (neg.seq.)
Phasor IL1T (neg.seq.)
Internal/
External Fault
Discriminator
and Sensitive
differential
protection
Calculation
negative
sequence
Idiff
Harm.
Block
Analog
Outputs
INTFAULT
EXTFAULT
OPENCT
OPENCTAL
en06000434-2.vsd
The sensitive protection is deactivated
above bias current > 150 % rated
current.
IEC06000434 V3 EN
Figure 54: Simplified principle design of the Generator differential protection GENPDIF
Simplified logic diagrams of the function are shown in figures 55, 56, 57 and 58.
Section 6 1MRK502052-UEN B
Differential protection
162
Technical manual