ABB Industrial IT enabled REX 521 - Introduction; General

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Technical Reference Manual, General
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This document provides a general description of the protection relay REX 521
Revision C. For more information about the earlier revisions, refer to section
“Revision history of REX 521” on page 49.
For detailed information about the separate functions, refer to
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(see “References” on page 51).
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The protection relay REX 521 is designed for protection, control, measuring and
supervision in medium voltage networks. Typical applications include incoming and
outgoing feeders as well as substation protection. The protection relay is provided
with energizing inputs for conventional current and voltage transformers. Also a
hardware version with inputs for current and voltage sensors is available.
The protection relay is based on a multiprocessor environment. The HMI
1
(human-
machine interface) including an LCD (liquid chrystal display) with different views
makes the local use easy and informs the user via indication messages. Modern
technology is applied both in hardware and software solutions.
The REX 521 is part of the substation automation concept for Distribution
Automation and extends the functionality and flexibility of the concept further.
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1. HMI is referred to as MMI (man-machine interface) in the relay and in the Relay
Setting Tool.