ABB REX 521 protective relay

ABB REX 521 protective relay

Hardware version and standard configuration

Hardware version standard configuration core functional characteristics application scenarios

Basic B01 three-stage non directional overcurrent and ground fault protection, thermal overload protection single bus system, radial isolated neutral point network

Basic B02 includes a single busbar system with automatic reclosing (1-5 times) and phase to phase circuit breaker protection that requires automatic reclosing

Medium M01 directional grounding fault protection, three-stage overcurrent compensation or isolated grounding network

Medium M02 directional grounding fault protection+automatic reclosing system with selective protection and reclosing required

High/Sensor H01 directional overcurrent and synchronization check, sensor version requires directional protection and synchronization function system

High/Sensor H07 motor protection (thermal overload, start-up supervision, phase sequence protection) for large three-phase motor drive

Core protection function

Overcurrent protection

Three stage formula: 3I>(low constant value), 3I>>(high constant value), 3I>>>(instantaneous)

Starting current range: 0.10-40.00 x In, operating time 0.05-300s

Earth fault protection

Non directional: Io>, Io>>, Io>>

Directional: Io>-->, Io>-->, Io>>-->, basic angle - adjustable from 90 ° to 60 °

Overvoltage/undervoltage protection

Overvoltage: 3U>(low setting), 3U>>(high setting), starting voltage 0.10-1.60 x Un

Undervoltage: 3U<(low setting), 3U<<(high setting)

frequency protection

F1 and F2 stages, frequency range 25-75Hz, df/dt protection accuracy ± 100mHz/s

Measurement and monitoring functions

Current/voltage measurement

3I: True RMS of three-phase current, range 0-20000A

3U: Three phase voltage, range 0-9999.99kV

Disturbance Record (DREC)

Can record 1-10 events, pre trigger time 0-100%, supports digital input triggering

Power Quality Monitoring

PQ 3Inf: Measurement of current harmonics, THD range 0-1000%

PQ 3Unf: Voltage harmonic measurement, in compliance with EN 50160 standard

Key parameters of application examples

Outgoing feeder (Basic B01)

Overcurrent protection: 3I>starting current 0.1-5 x In, operating time 0.05-300s

Ground fault protection: Io>starting current 1-500% In

Motor protection (High H07)

Thermal overload protection: time constant 0.1-999min, starting current 0.1-10 x In

Start supervision: Start time 0.3-250s, stall time 2-120s

Signal routing and parameterization

Digital input selector

Supports 16 functions including reset, blocking, disturbance recording triggering, etc

Output switch group (SWGRP)

Configurable Trip1-5, CBFP and other signals to output relays

interlocking logic

Support interlocking control based on circuit breaker status and grounding switch status

key issue

What are the hardware versions of REX 521? What are the core differences between each version?

Answer: REX 521 has three hardware versions: Basic, Medium, and High/Sensor. The Basic version provides basic overcurrent and ground fault protection; Medium adds directional protection function; The High/Sensor version has the most comprehensive features, including advanced functions such as synchronization check, frequency protection, motor protection, and some configurations support sensor input.

How to configure the automatic reclosing function of REX 521? How many times does it support overlap?

Answer: The automatic reclosing function (O ->I) can be configured with a start signal (such as overcurrent start or trip signal trigger) through the input switch group, supporting 0-5 reclosing times. The parameters such as dead time and startup delay for each overlap can be independently set, for example, H04 configuration supports a combination of high-speed overlap (dead time 300ms) and delayed overlap (2 minutes).

How does REX 521 achieve thermal overload protection in motor protection applications?

Answer: Implemented through the 3Ithdev>function block, based on the dual time constant model (independent calculation of stator and rotor), the thermal time constant (0.1-999min) and maximum temperature (50-350 ° C) can be set, and the startup current multiple (0.1-10 x In) and startup time (0.1-120s) configuration are supported. When the temperature exceeds the set value, a trip or alarm will be triggered.