I have a single breaker double bus station. Same for both high and low side voltages, 345kv to 115kv, 4 autotransformers.

The bus coupler has two MHO distance elements one looking in each direction; both set to reach at 10% of the shortest line and delayed by 8 cycles.

The transmission lines have an:

1. 80% Zone 1 set at 0 cycles

2. 125% Zone 2 at 35 cycles

3. A reverse zone 3 set at 16 cycles at 10% reach of the shortest line

4. A forward Zone 4 set at 65 cycles looking well beyond into the system.

I'm unsure what to do with the transformer's distance elements or how they will behave.

My desired outcome is that should a bus fault occur, the bus coupler will open about 10 cycles and then all the line breakers connected to the effected bus will trip in about 18 cycles in reverse zone with re-close blocked. I'd like the transformers connected to the effected bus to do the same via step distance elements; leaving the unaffected remaining bus, lines and trafos energized.

Here is a generic example of the scheme:

The bus coupler has two MHO distance elements one looking in each direction; both set to reach at 10% of the shortest line and delayed by 8 cycles.

The transmission lines have an:

1. 80% Zone 1 set at 0 cycles

2. 125% Zone 2 at 35 cycles

3. A reverse zone 3 set at 16 cycles at 10% reach of the shortest line

4. A forward Zone 4 set at 65 cycles looking well beyond into the system.

I'm unsure what to do with the transformer's distance elements or how they will behave.

My desired outcome is that should a bus fault occur, the bus coupler will open about 10 cycles and then all the line breakers connected to the effected bus will trip in about 18 cycles in reverse zone with re-close blocked. I'd like the transformers connected to the effected bus to do the same via step distance elements; leaving the unaffected remaining bus, lines and trafos energized.

Here is a generic example of the scheme:

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