Hi All,

I am completing an AFHA of a site that has numerous 3MVA, 35/0.48 kV transformers. These transformers have split secondary bushings on either side. There are also two cabinet doors for a single set of bushings. Between the doors there is a small, permanent section of the enclosure that effectively acts as a barrier at the end of the horizontal electrodes. See attached drawing snip and photo.

What are your thoughts on electrode configuration per IEEE-1584-2018? HCB seems most appropriate. However, I am thinking the barrier would block a substation portion of the AF event and any personnel in front of either access panel would experience some reduced amount of IE due to their proximity and position for access. In other words, the blast would not be directed at them.

I'd appreciate any feedback.

-Andrew

*substantial portion

Any opinions on this one?

It's closest to VCBB if the worker is at or near the plane of entry into the cabinet. Right in front, that panel will block a lot. But if you're at the side, the panel may direct the fireball towards you.

This is a tricky case. The barrier is likely to make things worse, purely because it'll make it more likely that the arcs can sustain themselves.