CHAPTER 8: AUTOMATION AUTOMATION LOGIC
D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL 485
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 also is asserted if the tap changer
remains between taps for more than 10 seconds. The lockout is latched until manually
reset.
Figure 421: Lockout automation logic
When DELTA_V is greater than 0.5 volts for more than 30 seconds (the sum of timers 2 and
3), the tap changer control is in auto mode, no overcurrent condition exists, and there is no
lockout, then a LOWER command is issued via analog virtual output 4. If the voltage
remains high, then subsequent LOWER commands are issued at five second intervals.
Figure 422: Lower command automation logic
When DELTA_V is less than –0.5 volts for more than 30 seconds (the sum of timers 2 and 3),
the tap changer control is in auto mode, no overcurrent condition exists, and there is no
lockout, then a RAISE command is issued. If the voltage remains low, then subsequent
RAISE commands are issued at five-second intervals.
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