ABB Relion 670 Series Technical Reference Manual page 403

Line differential protection ansi

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Table of Contents

1MRK505222-UUS C

Technical reference manual

Introduction

The Instantaneous residual overcurrent protection EFPIOC (50N) has a low transient

overreach and short tripping times to allow the use for instantaneous ground-fault

protection, with the reach limited to less than the typical eighty percent of the line at

minimum source impedance. EFPIOC (50N) can be configured to measure the residual

current from the three-phase current inputs or the current from a separate current input.

EFPIOC (50N) can be blocked by activating the input BLOCK.

Principle of operation

The sampled analog residual currents are pre-processed in a discrete Fourier filter

(DFT) block. From the fundamental frequency components of the residual current, as

well as from the sample values the equivalent RMS value is derived. This current value

is fed to the Instantaneous residual overcurrent protection (EFPIOC,50N). In a

comparator the RMS value is compared to the set operation current value of the

function (Pickup). If the residual current is larger than the set operation current a signal

from the comparator is set to true. This signal will, without delay, activate the output

signal TRIP.

There is also a possibility to activate a preset change of the set operation current via a

binary input (enable multiplier MULTPU). In some applications the operation value

needs to be changed, for example due to transformer inrush currents.

EFPIOC (50N) function can be blocked from the binary input BLOCK. The trip

signals from the function can be blocked from the binary input BLKAR, that can be

activated during single pole trip and autoreclosing sequences.

Function block

EFPIOC (50N)

ANSI06000269-2-en.vsd

ANSI06000269 V2 EN

EFPIOC (50N) function block

Current protection

Relion red670