Introduction; General - ABB REX 521 Technical Reference Manual, General

1MRS 751108-MUM
2.
2.1.
Protection Relay
Technical Reference Manual, General

Introduction

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
Machine Interface) including an LCD (Liquid Crystal 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.
Fig. 2.1.-1 REX 521 protection relay
1. HMI is referred to as MMI (man-machine interface) in the relay and in the Relay
Setting Tool.
REX 521
1
(Human-
9