ABB REX 521, Technical Reference Manual, General

Page: 6 / 64

6
1MRS 751108-MUM Protection Relay
Technical Reference Manual, General
REX 521
2. Introduction
This document provides a general description of the protection relay REX 521
Revision B. For more information about the earlier revisions, please refer to section
“Revision history of the REX 521” on page 42.
For detailed information about the separate functions, please refer to REX 521
Technical Reference Manual, Standard Configurations (1MRS 751802-MUM).
2.1. General
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
including
an LCD 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.
)LJ 5(;SURWHFWLRQUHOD\
1. HMI is referred to as MMI in the relay and in the Relay Setting Tool.