Short Line (around 2 km) Protection
Short Line (around 2 km) Protection
(OP)
Hey,
I would like to know if there would be any technical problem in protecting a 115 kV short overhead line (around 2 km) with distance relay and over current as back up.
The line is dual circuits between a ring substation and 2 outdoor type SF6 circuit breakers feeding 2 step-down transformers 115kV / 13.8 kV vector group DY1 with 400A NGR. The bus tie on the 115 kV side is normally closed while the bus tie on the 13.8 kV side is normally open.
I know that line differential would be better but this is the design we have and the project would be delayed significantly if we would have to change the scheme to differential. I just would like to know if distance would do? Because some are skeptic that the line is too short to be protected by distance relay.
Thanks
I would like to know if there would be any technical problem in protecting a 115 kV short overhead line (around 2 km) with distance relay and over current as back up.
The line is dual circuits between a ring substation and 2 outdoor type SF6 circuit breakers feeding 2 step-down transformers 115kV / 13.8 kV vector group DY1 with 400A NGR. The bus tie on the 115 kV side is normally closed while the bus tie on the 13.8 kV side is normally open.
I know that line differential would be better but this is the design we have and the project would be delayed significantly if we would have to change the scheme to differential. I just would like to know if distance would do? Because some are skeptic that the line is too short to be protected by distance relay.
Thanks






RE: Short Line (around 2 km) Protection
RE: Short Line (around 2 km) Protection
There is no link in your post!
RE: Short Line (around 2 km) Protection
http://eng-tips.com/viewthread.cfm?qid=319845
RE: Short Line (around 2 km) Protection
If there is no tie, but terminated in transformers, then there would be no problems,
RE: Short Line (around 2 km) Protection
There is no tie in the receiving end substation. The lines are directly terminated in the transformers via outdoor SF6 type circuit breakers.
The tie on the secondary side of the transformers is normally open.
So I guess the installation is ok.
The proposal is to set zone 1 to be over reaching and to delay it a bit to overcome any transients in the system.
The lines are treated as radial feeders.
RE: Short Line (around 2 km) Protection
A transformer differential can be used to clear the transformer quickly.
The problem with an over reaching zone is there either needs communications, time delay, or expect a coordination problem. For either a line or transformer fault the same customers will be out, so while it won't matter, operations people will expect coordition. Or you could try to convence them it dosen't matter, but that never worked for me.
Beware that for the low side tied, there may be an issue of a fault feed through the secondary to a high side fault. So it should be set up to operate the remote end of the lines for a line (transformer goes without saying)fault. This again can be with communications, or directional relaying.
I just believe what can be done by operations, will be done. So plan for it.
RE: Short Line (around 2 km) Protection
RE: Short Line (around 2 km) Protection
RE: Short Line (around 2 km) Protection
RE: Short Line (around 2 km) Protection
RE: Short Line (around 2 km) Protection