GE D90 Plus Instruction Manual page 436

AUTOMATION LOGIC
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Figure 355: Voltage difference automation logic
The current on each phase is checked to ensure that it is less than the maximum allowable
for a tap changer operation.
Figure 356: Overcurrent check automation logic
A lockout is implemented with the following logic. The lockout is asserted if the tap
changer gas trip contact is picked up (63GT). The lockout is also asserted if the tap changer
remains between taps for more than ten seconds. The lockout is latched until manually
reset.
Figure 357: Lockout automation logic
PLUS
D90 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 8: AUTOMATION