Transformer Differential with Reclosers

[rockman7892]

Is it possible to implement transformer differential protection using (2) reclosers on high and low side of transformer?

Looking at application where existing 15kV recloser would be on low voltage side of new 15MVA transform and consideration adding new 25MVA recloser on 25kV high side for primary protection and diff protection.

I know reclosers have their own integral protection & control modules for 50/51 etc... Is it possible to link (2) reclosers control units to perform a diff application or are separate external CT's and relaying needed. 15MVA falls in area recommended diff protection.

Any downsides to using reclosers for protection of a transformer. These reclosers will not utilize reclosing functionality.

 

[protoslash]

you definitely need a separate relay for the differential function, probably CT as well since it might not be possible to split the recloser ct output to the differential relay. the restricted earth fault element also need to CT the transformer neutral.

using the recloser as the interrupting device is alright if you can get the differential trip signal to the reclosers.

 

[jghrist]

Most microprocessor based recloser controls will have an input available that you could program to trip the recloser from the differential relay. Some may require an optional module.

Non-microprocessor controlled reclosers will not have that capability.

 

[bacon4life]

The SEL-651R has several options for communication aided tripping. It is not quite a differential, but it would be significantly faster than standard overcurrent relaying. SEL is also experimenting with some cutting edge schemes intended for detecting dropped conductors, perhaps those might function similarly to a differential.

 

[davidbeach]

With a pair of 651Rs communicating with each other across the transformer you could have a blocking scheme where the low-side seeing a fault would block the sensitive elements on the high-side. Wouldn't be quite as fast as true differential and wouldn't be as sensitive as a negative sequence differential or an REF, but it could still get you much faster tripping for lower level faults than you'd get with just time overcurrent. But if you want the major benefits of differential you ought to use something other than reclosers.

When one this sentence into the German to translate wanted, would one the fact exploit, that the word order and the punctuation already with the German conventions agree.

-- Douglas Hofstadter, Jan 1982

 

[cranky108]

It's been done with pre-microprocessor reclosers (not hydraulic). The early form 3 and 3A's could do this.
I would suggest a lockout be added, though.