GE Industrial Solutions Entellisys System User Manual - Manual (Page 147)

Introduction to FlexLogic 147
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11 FlexLogic™
11.1 Introduction to FlexLogic
To provide maximum flexibility to the user, the arrangement of internal digital logic combines
fixed and user-programmed parameters. Logic upon which individual features are designed is
fixed, and all other logic, from digital input signals through elements or combinations of
elements to digital outputs, is variable. The user has complete control of all variable logic
through FlexLogic™. In general, the system receives digital inputs, which it uses to produce
digital outputs.
The states of all digital signals used in Entellisys are represented by flags (or FlexLogic operands,
which are described later in this section). A digital “1” is represented by a “set” flag. Any
external-contact change-of-state can be used as an input to a control feature in a FlexLogic
equation or to operate a contact output. The state of the contact input can be viewed remotely
via the HMI. If more complex logic than presented above is required, it is implemented via
FlexLogic.
Traditionally, protective relay logic has been relatively limited. Any unusual applications
involving interlocks, blocking, or supervisory functions had to be hard-wired using contact
inputs and outputs. FlexLogic minimizes the requirement for auxiliary components and wiring
while making more complex schemes possible. The logic that determines the interaction of
inputs, elements, schemes and outputs is field programmable through the use of logic
equations that are sequentially processed.
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, or 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 1 (=ON, i.e., flag set) or 0 (=OFF, i.e., flag not set).
Each equation is evaluated twice every power system cycle.