How to install station class lightning arrestors at an oil filled transformer?

[bdn2004]

At the bottom of the picture are the arrestors that we are to install at this transformer.
I'm inquiring of the vendor right now asking for a detail, but I thought this forum could give me some quick advice.

There is a plate included that matches up to the bolt patterns at the back of the panel.

These are 18kV station class arrestors.

 

[jghrist]

Where are the transformer bushings? I would maintain the same clearances for the arresters as exists for the bushings. It really doesn't appear that you have enough clearance from the arresters to the side of the compartment. Assuming that the arresters are about 11-12" high, it looks like if you mount them where the bolts are, you will have only 3-4" clearance, not enough at 25 kV.

 

[bdn2004]

These came from this way, they are 18kV but they are operating at 13.8kV. Attached is the outline of the transformer. Where do you find the size/spec of the wire to use?

 

[jghrist]

You don't need any particular wire size for the connection between the bushing and the arrester because it won't carry any load current. #4 AWG copper would be fine.

I guess if ABB designed the installation, it must meet necessary NEMA standards for clearance, but it seems that one of the arresters is awfully close to the thermostat. It's probably OK for 13.8 kV. The photo shows 4-hole stud terminals on the arresters. You could increase clearances by using smaller terminals. It will be tricky terminating the cable to the bushings. The 2-hole pads are vertical which means that a terminator with a 2-hole pad will have to be vertical. The middle arrester is directly below the bushing; how to you get the terminator past the arrester?

 

[bdn2004]

I think the picture is a little deceiving. I don't think those 4 hole lugs are for the Lightning arrestors. Somebody just put that on there, they are not connected together.
Do you daisy chain the bottoms together to ground? And on the line side...I guess you lug a short #4 jumper a and connect between the the HV bushing and its corresponding arrestors? If so why doesn't this come preasssembled?
I'm not sure how they will finagle the cables to get them terminated.

 

[stevenal]

The 2-hole pads are vertical which means that a terminator with a 2-hole pad will have to be vertical

. So use a 1 hole termination pad and use the other hole for the arrester lug. Route cables so they bend out toward door and around so the terminators hit the bushings horizontally.

 

[bdn2004]

Actually they are going to use a 2 hole lug to terminate at the transformer. And use longer bolts and connect the jumpers onto these bolts also.