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Introduction
Main Relay Features
Overview
The Allen-Bradley 857 motor and feeder protection device includes
all the essential protection functions needed to protect feeders and
motors in distribution networks of utilities, heavy industry, power
plants and offshore applications. Further, the device includes many
programmable functions, such as arc protection (option), thermal,
trip circuit supervision and circuit breaker protection and
communication protocols for various protection and communication
situations.
This User Manual contains general descriptions of the functions of
the protection relay as well as installation and operation instructions. It
also includes instructions for parameterization and configuration of the
relay and instructions for changing settings.
This manual also includes detailed protection function descriptions
as well as application examples and technical data sheets.
The main features of the Allen-Bradley 857 device are:
•
Fully digital signal handling with a powerful 16-bit
microprocessor, and high measuring accuracy on all the setting
ranges due to a 16-bit A/D conversion technique
•
Wide setting ranges for the protection functions can reach a
sensitivity of 0.5%
•
Integrated fault location for short-circuit faults
•
The device can be matched to the requirements of the application
by disabling the functions that are not needed
•
Flexible control and blocking possibilities due to digital signal
control inputs (DI) and outputs (DO)
•
Easy adaptability of the device to various substations and alarm
systems due to flexible signal-grouping matrix in the device
•
Possibility to control six objects (e.g. circuit-breakers,
disconnectors)
•
Status of eight objects (e.g. circuit breakers, disconnectors,
switches)
•
Freely configurable display with six selectable measurement
values
•
Freely configurable interlocking schemes with basic logic
functions
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Chapter
857-UM001A-EN-P – July 2009
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