9328900990 Rev L BE1-951 Application 8-1
SECTION 8 • APPLICATION
INTRODUCTION
This section discusses application of the BE1-951 Overcurrent Protection System using the
preprogrammed logic schemes. The Details of Preprogrammed Logic Schemes subsection describes the
characteristics of each logic scheme and how they combine to create an Overcurrent Protection System
for a radial system substation. A detailed description of each preprogrammed scheme is also provided.
This section concludes with application tips for programming a custom logic scheme to meet the
requirements of your application.
The preprogrammed logic schemes are designed to accommodate most common distribution or sub-
transmission radial system overcurrent coordination schemes. The protection engineer can choose a
logic scheme that most closely meets his application practices and adapt it by changing the function block
operation and settings. This eliminates the need to create a custom logic scheme.
It should be noted that each preprogrammed logic scheme also illustrates typical ways of using or
controlling various functions. The user may choose to create a custom logic scheme by mixing the logic
from several of the preprogrammed schemes. The logic can also be modified to incorporate some of the
features described in the application tips provided at the end of this section. The flexibility of BESTlogic
allows the protection engineer to create a custom scheme that exactly meets the requirements of the
application.
EXPLANATION OF TERMS
The following paragraphs define terms that are used in the logic scheme discussions of this section.
Function Block - A stand-alone protection or control function that is equivalent to its discrete component
counterpart.
Torque Control - Blocks the start of an overcurrent function block. The pickup and trip outputs are held at
zero and the timing function is inhibited. This is in contrast to merely blocking the trip output. Torque
control applies to all overcurrent function blocks including those that don't emulate induction disk type (51)
relays.
Virtual Switches - Logic switches that emulate traditional switches used on relay and control panels.
Examples of these switches are breaker control switches (101) and selector switches (43). Virtual
switches can be operated via communication commands or the front panel human-machine interface
(HMI). Operation of a virtual switch can be disabled if the switch won't be used in a preprogrammed logic
scheme that includes the switch. Password protection is also available for the virtual switches.
Radial System - A system where the loads are fed from only one source at a time.
OVERVIEW OF PREPROGRAMMED LOGIC SCHEMES
Six preprogrammed logic schemes are available. A brief description of each preprogrammed logic
scheme is provided in the following paragraphs. More detailed information about these schemes is
provided in Details of Preprogrammed Logic Schemes.
BASIC-OC Logic Scheme (Basic Overcurrent Protection)
This logic scheme provides basic time and instantaneous overcurrent protection. Included protective
elements are phase, neutral, and negative-sequence overcurrent protection. Functions such as breaker
failure, virtual breaker control, automatic reclosing, and protective voltage features are not enabled in this
scheme. However, these features may be activated through BESTlogic.
CAUTION
If "NONE" logic is selected, the protection elements are not connected to the
virtual outputs or output relays and fault recording features including targets are
not enabled. The user will have to program and enable these features and
functions as part of building a custom logic scheme.
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