BE1-951
BESTlogic Programmable Logic
7-1
SECTION 7 • BESTlogic PROGRAMMABLE LOGIC
INTRODUCTION
Multifunction relays 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, 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 isn’t 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 Functions.
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.
