Changing a GE MDP with a SR750

[eaaf]

Good Day.
I want to change the source of power of a area of the plant where I work. Right now it is placed in a GE switchgear make in the 1997, which has a MDP (Digital Time Overcurrent Relay) make by GE, for the protection of the feeder with a capacity of 1200 amps at 4.16 KV. I want to move the cables to another feeder, some older that the actual, but it has a Multilin SR750 for protection of the feeder with 1200 amps at 4.16 KV. The reason of the change is to have the different areas feed from a transformer that feed similar equipments.
I want to know how I calculate the settings for the SR750 from the setting that MDP has.
I attach a picture of the MDP which shows the settings.
The CT for the MDP are 1000/5. An the other one has 1500/5 Ct's (for SR750).
The current in the feeder is 500 amps by the moment.
I tried with the formulas for the timing. But I can't get a curve that overlap in the logarithmic paper.
Can someone help me with the way that I have to make the calculation.

Thanks in Advance.

Regards.

EAAF

 

[rbulsara]

Paper???? Calculations?

Most of us now use a software....Even with paper, you need published TCC curves from the manufacturers at different settings.

If you do this often, get a software or pay someone to do it for you.

Rafiq Bulsara

http://www.srengineersct.com

 

[davidbeach]

Yep, sounds like you need to hire the assistance of someone locally who understands such things. If you are interested in learning, but that won't help for this project unless you have lots of time, try the protection references in faq238-1287.

 

[alehman]

Also, the SR750 has lots of other settings that will need to be evaluated. This will take a little time even for someone very familiar with these relays.

Alan
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"It’s always fun to do the impossible." - Walt Disney