Out of Step Protection for Stability

[timm33333]

I am trying to figure out what would be the acceptable/recommended settings for the out of step (78) protection relay for generator. (For example for loss of excitation(40) protection of generator, the recommended diameter of MHO circle is Xd and the recommended offset of MHO circle is Xd’/2.)

The distance relay (21) of generator has three zones: zone 1 is 80% of line impedance, zone 2 is 120% of line impedance, and zone 3 can be set as out of step (78) protection.

For out of step (78) protection, what would be the recommended settings of the diameter of MHO circle, offset of MHO circle, and blinder angle (δ)?

Thanks for help.

 

[davidbeach]

If you're required to meet the NERC compliance standards, those settings come from calculations performed by the Planner. It requires knowledge of both the generator and the surrounding system.

I’ll see your silver lining and raise you two black clouds. - Protection Operations

 

[timm33333]

Yes these would need calculations. I am just looking for some sample values, to get a feel that how these values look like. Thanks.

 

[timm33333]

I mean that what values can be assumed if the transient stability study report is not available?

 

[beyond86]

Example in attach. Calculation for Siprotec 4 7UM.

 

[timm33333]

Thanks. There is 21-distance protection for generator and also there is 21-distance protection for transmission line, are these two the same thing or are they different?