GE D30 Instruction Manual page 279

CHAPTER 5: SETTINGS
7. Now write the complete FlexLogic expression required to implement the logic, making an effort to assemble the
equation in an order where Virtual Outputs that are used as inputs to operators are created before needed. In cases
where a lot of processing is required to perform logic, this can be difficult to achieve, but in most cases does not cause
problems as all logic is calculated at least four times per power frequency cycle. The possibility of a problem caused by
sequential processing emphasizes the necessity to test the performance of FlexLogic before it is placed in service.
In the following equation, virtual output 3 is used as an input to both latch 1 and timer 1 as arranged in the following
order:
DIG ELEM 2 OP
Cont Ip H1c On
NOT
AND(2)
= Virt Op 3
Virt Op 4 On
Virt Op 1 On
Virt Op 2 On
Virt Ip 1 On
DIG ELEM 1 PKP
XOR(2)
Virt Op 3 On
OR(4)
LATCH (S,R)
Virt Op 3 On
TIMER 1
Cont Ip H1c On
OR(3)
TIMER 2
= Virt Op 4
END
In this expression, the virtual output 4 input to the four-input OR is listed before it is created. This is typical of a form of
feedback, in this case, used to create a seal-in effect with the latch, and is correct.
8. Always test the logic after it is loaded into the relay, in the same way as has been used in the past. Testing can be
D30 LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
Figure 5-70: FlexLogic equation for virtual output 4
FLEXLOGIC
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