Reverse Blocking Bus Bar Protection

Medium voltage bus bar protection is often implemented using Reverse Blocking so called "Reverse Blocking" where the start element of the outgoing feeders is used to block the instantaneous element of the incomer and bus section.

This is an IDEAL application for GOOSE.
Each downstream PTOC.Str is published on the LAN
The upstream and bus section IED's would subscribe to all those messages and use them for their PTOC.BlkRef
i.e. if any downstream PTOC.Str = true, then the upstream PTOC is blocked.

Note the bus section would need directional controlled PTOC so you have to block the correct direction.

Expected time: if there is a bus fault the downstream PTOC.Str are all False so there is no blocking of the upstream PTOC. The upstream PTOC will operate in whatever time they are configured for (probably a short time delay to make sure there is no "race" between the downstream feeder relays and the upstream for a fault on the feeder)

  It is also wise to then should consider CIrcuit Breaker Failure with the use of RBRF so that an uncleared feeder fault will still result in clearance by the upstream relays.

As in all these things, also give consideration as to how you implement the GOOSE message subscriptions so that you minimise or preferable eliminate the need to reconfigure existing devices when bays are added in the future.

Normally with no fault anywhere, the feeders are each publishing their individual GOOSE with PTOC=False ,
i.e. suppose there are 10 outgoing feeders.
There are therefore 10 individual GOOSE messages each containing a bit that represents
Fdr1PTOC.Str=False
Fdr2PTOC.Str=False
Fdr3PTOC.Str=False
...
Fdr10PTOC.Str=False
These 10 messages are repeated every 1 second.

The incomer and the bus section are the Subscribers.
Each subscribes to the 10 GOOSE messages. They are configured as I said before that any of the received GOOSE change to PTOC.Str=True will BLOCK the incomer and the bus section.

Hence if there is a Fault on Feeder 3, the Published Goose messages will be
Fdr1PTOC.Str=False
Fdr2PTOC.Str=False
Fdr3PTOC.Str=TRUE
...
Fdr10PTOC.Str=False
Hence the incomer and the bus section will not trip because of the one GOOSE message containing True.
Feeder 3 will still operate to clear the fault on the feeder.

If there is a bus fault, the outgoers will still all be publishing False since they are not seeing any fault current flowing out onto the Feeders i.e. PTOC.Str=False.

Therefore the incomer and the bus section subscribing to all 10 messages don't receive any with a bit =True, they do not block and so they can trip according to their operating settings - pickup, curve and time delay.

Extra Notes: