Overcurrent Relay CO

CO relays, a complete coordinated line, assure accurate and reliable primary or backup protection against phase or ground faults. They provide the back-bone of any protective relaying system, from generator to load.

For selective coordination between relays, seven different time curve characteristics are available. All are designed to operate faster at higher fault currents. Each type has a wide range of current tap settings and time dial positions.

Properly applied, CO relays will provide maximum service continuity by ripping the fewest possible circuit breakers required to disconnect a faulted section.

Hi-Lo CO
CO, Hi-LoHi-Lo CO induction-disc type overcurrent relays are activated when the current in them exceeds given values. The circuit closing type relays are normally used to trip a circuit breaker. They may have either single or double contacts for tripping one or two circuit breakers.

The complete, coordinated line assures accurate, reliable primary and backup protection for phase or ground faults. Seven different time curves are available for system coordination.

The Hi-Lo CO relay offers two wide ranges: a high and a low.

Hi Range
The "Hi" range has an induction-disc time unit, rated 1 to 12 amperes with 14 taps. To complement the time unit, the relay is available with an instantaneous unit rated 6 to 144 amperes with three tap positions. The core screw of the instantaneous unit is used to set the actual current pickup within any one of the three ranges.

The 1 - 12 ampere time unit along with the 6 - 144 ampere instantaneous unit in one relay style offers considerable savings in stocking and flexibility of application. This one rating will satisfy the phase and ground requirements in most cases.

Lo Range
The "Lo" range CO contains the same 0.5 to 2.5 ampere induction-disc time unit with 7 taps as standard CO relay designs. However, the instantaneous unit has a wide range of 2 to 48 amperes using 3 taps. The core screw of the instantaneous unit is used to set the actual current pickup within the range used.

The 0.5 - 2.5 ampere time unit and 2 - 48 ampere instantaneous unit combination result in substantial stock advantage of relays for ground fault protection and other low current applications.


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    ABB contact for United States of America

    Sales: Pete Kovacic
    Service: Glenn Goldfarb
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