Relay Curve Types...

[whycliffrussell]

I'm doing an arc flash study using ETAP software. Under one of the relays models (Alstom) there is an option for ieee very inverse curves and iec very inverse curves! I understand that IEEE-VI and IEC-V has completely different trip time equations and hence the time current characteristics are different. How am I to know which to use?

 

[wbd]

I would say it would be dependent on which is the accepted standard in your country. In the USA, I would use the ANSI/IEEE curve. In Europe, the IEC.

 

[jghrist]

Are you setting the relays or using existing settings for the arc flash study? If you are using existing settings, you will have to determine which curves are used in the existing settings. If you are setting the relays, I'd follow wbd's advise.

 

[DanDel]

Most of the relays that have multiple curve options only allow either the IEEE or the IEC curves, not both. This data should be available from the relay model number.