ABB Industrial IT enabled REX 521 Technical Reference Manual, General page 7

Protection relay

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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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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

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.

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(see "References" on page 51).

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(human-