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Settings calculation BB protection HV network

Settings calculation BB protection HV network

Settings calculation BB protection HV network

(OP)
Please can you inform based on experience settings Id and Istab of BB protection of type relay siprotec Low impedance numerical protection 7SS/
In the substation when there are different ratio of CT from the smalest 200/1A and bigest ratio 2000/1 in bus coupler there will be problem of saturation in these case for external short circuit  

RE: Settings calculation BB protection HV network

Hi.
You must read recommendation of mnf.
Possible few option of calculation.
This difference ie not so important 2000:200A 10:1 , nothing for this protection. You can choice setting about 80% of max load current on the station, or used 2000A, as max load current and put setting on the 1600A. Istab is angel in this protection, if I remember right.

Saturation is not problem, 7SS5 have all algorithms, problem is second SC, in the same time, at zone of BB.

Best Regards.
Slava

RE: Settings calculation BB protection HV network

(OP)
yes right Istab is angle. The differential current Id>kIstab, k=0.10-0.80. The question is wich factor "k" used for differential current/

RE: Settings calculation BB protection HV network

I will check with guys from Siemens and will back to you.

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