ABB REU 523 Combined Overvoltage and Undervoltage Relay

The REU 523 is intended for overvoltage and undervoltage protection in medium

voltage distribution networks but can also be used for protection of generators,

motors and transformers.

The REU 523 continuously evaluates the fundamental wave of the three phase-to

phase voltages. In addition, the high-set undervoltage stage can be configured to

evaluate either only one instead of three phase-to-phase voltages or the

positive-phase-sequence voltage.

The REU 523 is based on a microprocessor environment. A self-supervision system

continuously monitors the operation of the electronics and the software.

The HMI includes a Liquid Crystal Display (LCD) which makes the local use of the

relay safe and easy.

Local control of the relay can be carried out using a portable computer connected to

the front connector and remote control via the rear connector connected to the

distribution automation system through the serial interface and the fibre-optic bus.

Features

• Single- or three-phase use

• High-set overvoltage stage with definite-time or inverse definite minimum time

(IDMT) characteristic

• Low-set overvoltage stage with definite-time or IDMT characteristic

• High-set undervoltage stage with definite-time or IDMT characteristic

• Low-set undervoltage stage with definite-time or IDMT characteristic

• Positive-phase-sequence protection

• Adjustable drop-off/pick-up ratio for the low-set over and undervoltage stages

• Circuit-breaker failure protection (CBFP)

• Disturbance recorder

• recording time up to 12 seconds

• triggering by a start or a trip signal from any protection stage and/or by a binary

input signal

• records three analogue channels and eight digital channels

• adjustable sampling rate

• Non-volatile memory for

• up to 60 event codes

• setting values

• disturbance recorder data

• recorded data of the five last events with time stamp

• number of starts for each stage

• alarm indication messages and LEDs showing the status at the moment of

power failure

• Three accurate voltage inputs

• Galvanically isolated binary input with a wide input voltage range

• All settings can be modified with a personal computer

• HMI with an alphanumeric LCD and manoeuvring buttons

• IEC 60870-5-103 and SPA bus communication protocols

• Two normally open power output contacts

• Two change-over signal output contacts

• Output contact functions freely configurable for desired operation

• Optical PC-connector for two-way data communication (front)

• RS-485 connector (rear) for system communication

• Continuous self-supervision of electronics and software. At an internal relay fault

(IRF), all protection stages and outputs are blocked.

• User-selectable rated frequency 50/60 Hz

• User-selectable password protection for the HMI

• User-selectable nominal voltage 100/110/115/120 V

• Display of primary voltage values

• Demand values

• Multi-language support