404 D90
PLUS
LINE DISTANCE PROTECTION SYSTEM – INSTRUCTION MANUAL
PROTECTION FLEXLOGIC CHAPTER 7: PROTECTION
The logic that determines the interaction of inputs, elements, schemes and outputs is
programmable through the use of logic equations that are sequentially processed. The use
of virtual inputs and outputs in addition to hardware is available internally and on the
communication ports for other relays to use (distributed FlexLogic).
FlexLogic allows users to customize the relay through a series of equations that consist of
operators and operands. The operands are the states of inputs, elements, schemes and
outputs. The operators are logic gates, timers and latches (with set and reset inputs). A
system of sequential operations allows any combination of specified operands to be
assigned as inputs to specified operators to create an output. The final output of an
equation is a numbered register called a virtual output. Virtual outputs can be used as an
input operand in any equation, including the equation that generates the output, as a seal-
in or other type of feedback.
A FlexLogic equation consists of parameters that are either operands or operators.
Operands have a logic state of 1 or 0. Operators provide a defined function, such as an
AND gate or a timer. Each equation defines the combinations of parameters to be used to
set a virtual output flag. Evaluation of an equation results in either a logic 1 state (=ON, flag
set) or logic 0 state (=OFF, flag not set). Each equation is evaluated at least four times every
power system cycle.
Some types of operands are present in the relay in multiple instances (for example, contact
and remote inputs). These types of operands are grouped together (for presentation
purposes only) on the faceplate display. The characteristics of the different types of
operands are tabulated as follows.
Table 22: Protection FlexLogic operand types
Type State Example Characteristics (input is logic 1 or “on” if...)
Contact
input
On
CONT IP1 ON Voltage is presently applied to the input
(external contact closed)
Off
CONT IP1 OFF Voltage is presently not applied to the input
(external contact open)
Contact
output
Voltage on
CONT OP1 VON Voltage exists across the contact
Voltage off
CONT OP1 VOFF Voltage does not exist across the contact
Current on
CONT OP1 ION Current is flowing through the contact
Current off
CONT OP1 IOFF Current is not flowing through the contact
Digital
counter
Greater than
COUNTER 1 HI The number of pulses counted is above the set
number
Equal to
COUNTER 1 EQL The number of pulses counted is equal to the
set number
Less than
COUNTER 1 LO The number of pulses counted is below the set
number
Direct
input
On
DIRECT INPUT 1 ON The direct input is presently in the ON state
Element
(analog)
Pickup
PHASE TOC1 PKP The tested parameter is presently above the
pickup setting of an element that responds to
rising values or below the pickup setting of an
element that responds to falling values
Dropout
PHASE TOC1 DPO This operand is the logical inverse of the
pickup operand
Operate
PHASE TOC1 OP The tested parameter has been above/below
the pickup setting of the element for the
programmed delay time, or has been at logic
1 and is now at logic 0 but the reset timer has
not finished timing
Block
PHASE TOC1 BLK The output of the comparator is set to the
block function
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