Alstom SHPM 101 - Biased Neutral Current Level Detectors

SERVICE MANUAL R5888C
QUADRAMHO Chapter 2
Appendix A
Page 51 of 71
Figure 58: Biased neutral current level detectors
PRECISION FULL WAVE
RECTIFIER
FAST CHARGE
SLOW CHARGE
V
REF
LOW SET
V
REF
HIGH SET
LIMITS MAXIMUM VALUE
OF V
REF
BIASED REFERENCE LEVEL
BASE REFERENCE
LEVEL
IZ
A
IZ
B
IZ
C
+
–
+
–
+
–
GREATEST |PHASE DIFFERENCE CURRENT|+ I
n
(AMPS)
PHASE-FAULT
COMPARATORS
ENABLED
0.1 1 10 34 100
(Slope = 0.1)
|NEUTRAL CURRENT | + In (AMPS)
GROUND-FAULT
COMPARATORS ENABLED
10
1
0.16
0.1
0.02
HIGH-SET NEUTRAL
CURRENT DETECTOR
LOW-SET NEUTRAL
CURRENT DETECTOR
(Slope = 0.76)