240kV transmission line protection

[singuru]

I am working on a 240/144kV transmission line protection, in a Utility, Canada. I am fairly a new protection engineer. The philosophy is as follows:

They are using POTT schemes with the exception of PUTT at generation sites. There's evan a PUTT on one end and POTT on the other.

For short lines they are still using POTT schemes. They aren't comfortable using DCB, DCUB, or other hybrid pilot schemes.

PUTT shemes are immune to current reversals but they provide less fault resistance coverage which can be an issue (here we use 20 ohms). I think there is a provision in SEL relay, which uses Mirrored Bits communication to add an option for current reversal immunity in POTT scheme.

This is my overall understanding. Can anyone explain me in detail, the advantages of POTT scheme and are the other utilities using this scheme for any specific reason?

Thanks

 

[Marmite]

Lets hope that all those TLA's and FLA's mean something sensible to someone. They certainly don't to me.
TTFN
MRM8.

 

[singuru]

I mean POTT: Permissive over-reaching Transfer Trip
PUTT: Permissive under-reaching Transfer Trip
DCB: Directional Comparison Blocking
DCUB: Directional Comparison Unblocking

 

[davidbeach]

POTT is an extremely common protection scheme. The scheme in SEL relays called POTT is much more than the traditional definition of POTT and deals with reversal problems, weak infeed, and other weaknesses of traditional POTT.