Changing a GE MDP with a SR750
Changing a GE MDP with a SR750
(OP)
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
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






RE: Changing a GE MDP with a SR750
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
RE: Changing a GE MDP with a SR750
RE: Changing a GE MDP with a SR750
Alan
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"It's always fun to do the impossible." - Walt Disney