IAC Relay Curves?

[Kiribanda]

Hello all,

We everybody know that protective relay characteristics curves (Normal, Inverse, Very Inverse and Ex. Inverse etc) are defined as ANSI curves (IEEE C37.112) and IEC curves (IEC 60255).

Then what are "IAC" relay curves. Could anybody explain

1) For what does IAC stand for?

2) The relevant standard if any?

Thanks!

KIRIBANDA

 

[jghrist]

IAC is a General Electric electromechanical overcurrent relay. Characteristic curves of electromechanical overcurrent relays are the result of electrommagnetic and spring torques, and do not follow ANSI or IEC equations. The characteristic curves of electromechanical relays are developed by testing. The ANSI and IEC curves approximate the characteristics of electromechanical relays. You can fit the IAC curves to an equation that has the same general form as the ANSI and IEC curves; this is how computer aided coordination programs work.

 

[raisinbran]

The equations for the various relay types (ANSI, IEC, IAC, etc.) are given in the GE Multilin relay manual. There are also some sample points worked out for the various relay types. This manual is available over the internet at

http://www.geindustrial.com.

Regards,
Raisinbran

 

[cuky2000]

1.- For what does IAC stand for?
This is the code selected by the manufacturer for the electromechanical family of time inverse. Probably means Inverse Alternate Current (IAC) See the enclose links.

http://www.geindustrial.com/products/manuals/iac/iac51n.pdf

http://www.geindustrial.com/products/brochures/iac.pdf

2.- The relevant standard if any?
Relays manufacturer are not required to comply with standards in this matter. However, most manufacturers facilitate relay coordination by using the standard values as shown in the enclose sketch. See IEEE and IEC standards for additional details.

 

[ijl]

It seems that the "IAC" refers to relays from General Electric. The equation and constants for these relays are:

from

http://www.geindustrial.com/products/manuals/m60/m60man-j1.pdf

You can test this (and several other) curves with the power analysis program downloadable at

http://pp.kpnet.fi/ijl

 

[Kiribanda]

Hi all,

Thanks a lot for all your answers. It is a very valuable forum to be in touch always.

Cheers!!

Kiribanda :-D