Blocking Pilot POTT schemes for GOAB switching 2

[lansford]

For a 138KV fiber optic POTT scheme on network lines with a POTT instanteous O/C ground setting of about 300 amps, does your utility block the scheme during GOAB (group operated air break switching) on the lines?
thanks JIM

 

[bacon4life]

After a false trip on a scheme like that, we moved the instantaneous ground overcurrent setting up above the largest possible ground current due to one or two poles open. That project was a good example of how using every available element when upgrading from electro-mechanical relays to microprocessor based relays can lead to new types of incorrect trips. Also be sure any negative sequence elements are secure during GOAB.

 

[davidbeach]

So, then how do you detect open conductor "faults"? As we change from ground overcurrent to ground distance we tend to loose sensitivity to open conductors and I'm not always sure that is a good thing.

 

[bacon4life]

I don't think we have coverage for all open conductor situations. It is a parallel line from a remote generation site that also has tapped load, so the flow is often zero at some point on the line.

The instantaneous elements are set above the pole disagreement level with some more sensitive elements set to trip on a time delay.