Introduction; Principle Of Operation - ABB Relion 670 Series Technical Reference Manual

Section 7
Current protection
7.2.1
7.2.2
382
Function description
Four step phase overcurrent protection

Introduction

The four step phase overcurrent protection function OC4PTOC (51/67) has
independent inverse time delay settings for step 1 and 4. Step 2 and 3 are always
definite time delayed.
All IEC and ANSI inverse time characteristics are available together with an optional
user defined time characteristic.
The directional function is voltage polarized with memory. The function can be set to
be directional or non-directional independently for each of the steps.
Second harmonic blocking level can be set for the function and can be used to block
each step individually

Principle of operation

The Four step phase overcurrent protection OC4PTOC (51/67) is divided into four
different sub-functions, one for each step. For each step x , where x is step 1, 2, 3 and
4, an operation mode is set by DirModeSelx: Disable/Non-directional/Forward/
Reverse.
The protection design can be decomposed in four parts:
• The direction element
• The harmonic Restraint Blocking function
• The four step over current function
• The mode selection
If VT inputs are not available or not connected, setting parameter
DirModeSelx shall be left to default value, Non-directional.
IEC 61850 IEC 60617
identification identification
OC4PTOC
3I>
4
alt
4
TOC-REVA V1 EN
1MRK505222-UUS C
ANSI/IEEE C37.2
device number
51/67
Technical reference manual