Question on Line Differential Application
Question on Line Differential Application
(OP)
HI all,
I would like to tap on protection gurus here. Can a line differential relay work on lines with multiple substation taps on them?
I asked this because in one of our client transmission system, the 69kV overhead line from Main-Tie-Main GIS switchgear has a line differential GE L90 going into a remote substation also having GE L90 and communicates via fiber optic using IEC 61850 protocol. Now between, these lines, a new substation will be tapping off. My concern that they required us to place another line differential which I am doubting if this even going to work.
Your help is very much appreciated for my understanding.
Regards
I would like to tap on protection gurus here. Can a line differential relay work on lines with multiple substation taps on them?
I asked this because in one of our client transmission system, the 69kV overhead line from Main-Tie-Main GIS switchgear has a line differential GE L90 going into a remote substation also having GE L90 and communicates via fiber optic using IEC 61850 protocol. Now between, these lines, a new substation will be tapping off. My concern that they required us to place another line differential which I am doubting if this even going to work.
Your help is very much appreciated for my understanding.
Regards






RE: Question on Line Differential Application
RE: Question on Line Differential Application
With SEL products, you can use tap line protection. This allows you to apply a time overcurrent differential setting that would be set to coordinate with downstream protection off the tap.
Finally, you can make sure the minimum differential pickup is where it won't detect through faults on the new substation transformer. Faults on high side would cause the line to trip in this case.
RE: Question on Line Differential Application
RE: Question on Line Differential Application
I think that you could set negative and ground 87 elements and be good if all the tapped transformers have delta high sides.
RE: Question on Line Differential Application
We also supervise with a distance element, which helps.
RE: Question on Line Differential Application
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Question on Line Differential Application
RE: Question on Line Differential Application
You should have all the three devices with two communication channels so that each one communicates with the other two simultaneously. In case a link fails, one of the devices remains performing 87L function as a master and sends a transfer trip to the other two in case of a fault.
The multi ended fault location algorithm also works with 3 terminals.
Regards,
Charlie