ABB CO Instruction Leaflet

Effective : January 1997
Supersedes 41-100I, Dated January 1990
( | ) Denotes Change Since Previous Issue
®
File No. E103204
!
Before putting relays into service, remove all
blocking which may have been inserted for the
purpose of securing the parts during shipment,
make sure that all moving parts operate freely,
inspect the contacts to see that they are clean
and close properly, and operate the relay to
check the settings and electrical connections.
The following describes typical applications of the CO Relay:
RELAY TIME
TYPE CURVE
CO-2 Short
CO-5 Long
CO-6 Definite
CO-7 Moderately Inverse
CO-8 Inverse
CO-9 Very Inverse
CO-11 Extremely Inverse
All possible contingencies which may arise during installation, operation or maintenance, and all details and
variations of this equipment do not purport to be covered by these instructions. If further information is desired
by purchaser regarding this particular installation, operation of maintenance of this equipment, the local Asea
Brown Boveri representative should be contacted.
Courtesy of NationalSwitchgear.com
ABB Power T&D Company Inc.
Power Automation & Protection Division
Coral Springs, FL 33065
CAUTION
1) Differential protection where saturation of current transformers is not ex-
pected, or where delayed tripping is permissible.
2) Overcurrent protection, phase or ground, where coordination with down-
stream devices is not involved and 2 to 60 cycle tripping is allowable.
Motor locked rotor protection where allowable locked rotor time is
approximately between 10 and 70 seconds.
Overcurrent protection where coordination with downstream devices is not
involved and CO-2 is too fast. The operating time of this relay does not vary
greatly as current level varies.
1) Overcurrent protection where coordination with other divices are re-
quired, and generation varies.
2) Backup protection for relay on other circuits.
1) Motor Protection where allowable locked rotor time is less than 10 sec.
2) Overcurrent protection where coordination with fuses and reclosers is in-
volved, or where cold load pickup or trnsformer inrush are factors.
Type CO (HI-LO)
Overcurrent Relay
1. APPLICATION
The CO Relay is a single phase non-directional
time overcurrent device. It is used to sense current
level above the setting and normally is used to trip
a circuit breaker to clear faults. A wide range of
characteristics permit applications involving coordi-
nation with fuses, reclosers, cold load pickup, motor
starting, or essentially fixed time applications. AC
trip applications are described, but they are not rec-
ommended except in applications where a fault will
not reduce the ac voltage below a level at which
tripping will be reliable.
TYPICAL APPLICATIONS
Instruction Leaflet
41-100J