Basler Electric BE1-851 - Manual (Page 157)

SECTION 8 • APPLICATION
General
This section discusses application of the BE1-851 Overcurrent Protection System using the pre-
programmed 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.
NOTE
All preprogrammed schemes are shown for sensing input type H relays.
Relays with sensing input type G do not have negative-sequence elements.
Explanation of Terms
The following terms and definitions will facilitate the understanding of the application discussions to follow.
Function Block - A stand-alone protection or control function that is equivalent to its discrete component
counterpart.
Torque Control - Torque control refers to blocking the start of an overcurrent function block. The pickup
and trip outputs are held to zero and the timing function is not allowed to operate. This is in contrast to
merely blocking the trip output. This applies to all overcurrent function blocks including those that do not
emulate induction disk type (51) relays.
Virtual Switches - These logic switches emulate traditional switches used on relay and control panels
such as the breaker control switch (101) and selector switches (43). Virtual switches may be operated via
communication commands or the human-machine interface (HMI). Operation of these switches can be
disabled or password protected if the user chooses not to use them without changing the preprogrammed
BESTlogic schemes.
Radial System - As used in this section, a radial system is one where the loads are fed from only one
source at a time.
9289900990 Rev R BE1-851 Application 8-1