9328900990 Rev L BE1-951 BESTlogic Programmable Logic 7-1
SECTION 7 • BESTLOGIC PROGRAMMABLE
LOGIC
INTRODUCTION
Multifunction relays such as the BE1-951 Overcurrent Protection System are similar in nature to a panel
of single-function protective relays. Both must be wired together with ancillary devices to operate as a
complete protection and control system. In the single-function static and electromechanical environment,
elementary diagrams and wiring diagrams provide direction for wiring protective elements, switches,
meters, and indicator lights into a unique protection and control system. In the digital, multifunction
environment, the process of wiring individual protection or control elements is replaced with the entry of
logic settings. The process of creating a logic scheme is the digital equivalent of wiring a panel. It
integrates the multifunction protection, control, and input/output elements into a unique protection and
control system.
BESTlogic is a programming method used for managing the input, output, protection, control, monitoring,
and reporting capabilities of Basler Electric's digital, multifunction, overcurrent protective relay systems.
Each relay system has multiple, self-contained function blocks that have all of the inputs and outputs of its
discrete component counterpart. Each independent function block interacts with control inputs, virtual
outputs, and hardware outputs based on logic variables defined in equation form with BESTlogic.
BESTlogic equations entered and saved in the relay system's nonvolatile memory integrate (electronically
wire) the selected or enabled protection and control blocks with control inputs, virtual outputs, and
hardware outputs. A group of logic equations defining the function of the multifunction relay is called a
logic scheme.
Several preprogrammed logic schemes are stored in relay memory. Each scheme is configured for a
typical protection application and virtually eliminates the need for "start-from-scratch" programming. Any
of the preprogrammed schemes can be copied and saved as the active logic. Preprogrammed logic
schemes can also be copied and then customized to suit your application. Detailed information about
preprogrammed logic schemes is provided later in this section.
BESTlogic is not used to define the operating settings (pickup thresholds and time delays) of the
individual protection and control functions. Operating settings and logic settings are interdependent but
separately programmed functions. Changing logic settings is similar to rewiring a panel and is separate
and distinct from making the operating settings that control the pickup thresholds and time delays of a
relay. Detailed information about operating settings is provided in Section 4, Protection and Control.
WORKING WITH PROGRAMMABLE LOGIC
BESTlogic uses two types of logic settings: output logic settings and function block logic settings. These
two types of settings are discussed in the following subsections. Output logic settings are entered in
equation form and control the hardware outputs of the relay. BESTlogic function blocks are illustrated in
Figures 7-1 and 7-2 and are discussed in the following paragraphs.
Names assigned to inputs, outputs, timers, and protection and control elements represent the logic
variables in the equations.
Table 7-1 lists the logic variable names and descriptions.
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