High voltage pole switch

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websparky

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Cleveland, Ohio
Here are three photos of an old pole mounted high voltage switch I discovered this week as I was driving through rural Ohio. (They are large for clarity.)

Could someone could maybe help me understand the operation of the pieces I see at the top of the pole? Just curious!

Thanks!

Photos

[ August 26, 2005, 06:02 PM: Message edited by: websparky ]
 
Re: High voltage pole switch

Oh, no. I'm just wondering how it works. It is interesting to see an old one on a pole along side the country road. It has the handle insulated via a piece of wood and wood is used at other links also.
 
Re: High voltage pole switch

Not quite sure how the mechanical linkage functions to open and close the blade and stationary contact on this air break switch.

As the switch in the picture is opened from the closed position as shown, the horizontal metal horn attached to the blade rotates counterclockwise. Between this horn and the vertical one shown an arc forms as a result. With the switch being opened further, means a longer arc, until when it breaks and is extinguished.
 
Re: High voltage pole switch

I never saw the 'next' button up top.

I'm not sure how to explain how I think it works.

I thought you were getting at something else. It appears like the ground wire is busted?
 
Re: High voltage pole switch

The mechanism itself is just mechanical. As the switch is opened, contact is maintained on the long wires that rub against each other to prevent arcing in the contacts and to make the break up away from the equipment at the top of the pole. The wood is used to add a bit of insulation at top from phase to phase in the same manner as the wood piece in the handle. The ground rod at the bottom and the grounding wire is attached to the bottom part by a flexible braided strap to ground the operating handle. The ground wire is not broken, it is for safety of the operator and you do not want grounding at the top of the pole where you will be drawing an arc. At these voltages, using the earth for safety grounding makes sense.

Nice pictures of an old 15 kV, air break switch. :D
 
Re: High voltage pole switch

Thanks for the great descriptions of how it operates and what it is. My new job takes me through the rural areas of Ohio and I imagine I will be seeing more of these old electrical devices!
 
Re: High voltage pole switch

I will be seeing more of these old electrical devices!
Click to expand...
Dave, they are not necessarily that old. The newer ones usually have fiberglass instead of wood but look about the same. For what it is worth, we still put them up but not too often. :D
 
Re: High voltage pole switch

Originally posted by charlie:
Dave, they are not necessarily that old. The newer ones usually have fiberglass instead of wood but look about the same. For what it is worth, we still put them up but not too often. :D
Click to expand...
Charlie I see a lot of these in this area but I have also lately noticed that some appear to be converted to remote control.

The mechanical linkage gets shortened and run into a gray box that has what looks like a cellular antenna on it.

Am I on track or way off.
 
Re: High voltage pole switch

I believe they are loop isolation switch's
Most local feeds from the substation are fed in a loop that has these isolation switch's to isolate out any section of the loop that has a fault, this allows the rest of the circuit to be kept live to keep as many customer's on as possible.

Ok Charlie Am I close? :D

[ August 28, 2005, 02:33 AM: Message edited by: hurk27 ]
 
Re: High voltage pole switch

The switches we use are normally individual inline switches but we sometimes use gang operated switches that are radio controlled. We will close in a line at one location and open it in another location to shift load. This process changes the available fault currents and makes it impossible to give someone the correct numbers for calculating arc blast.

If someone were to hit a pole, a tree limb come down, or anything else to interrupt service, the remote switches could be used to isolate the damaged line. Since our system is compact, we have trouble men working 24/7 to do the manual switching in the field and there are some locations where we use the ground operated switches. Also, a primary metered customer is required to have a ground operated disconnecting means if he has control of his equipment behind the meter.

As far as the "deadman" switch, the grounding of the handle will work where the voltage is in our distribution voltages. We use 13.2 kV so plug 7.62 kV into Ohms law with 40 &#8486 of resistance and see how much current will flow. :D
 
Re: High voltage pole switch

These switches can't be that old, I repaired several of them used as transformer disconnects at the aluminum plants. (WWII vintage.)

What is hard to see in the picture is the knuckle joint that translates the rotary motion of the rear insulator into the vertical lifting of the arm on opening and the rotation of the arm on closing. (The contacts rotate 30-45 degrees after they are closed to get a good contact.)

When the switches get old, the cement joint between the ceramic insulator and the rotating pin can break. When we swung the handle only 2 of the 3 phases opened up. Fortunately, our lead electrician checked everything before applying grounds or it would have been a dead man switch.
 
Re: High voltage pole switch

It looks like the switch can be operated by anyone (like the handle goes down to the ground).

Could someone could maybe help me understand the operation of the pieces I see at the top of the pole? Just curious!
Click to expand...
Why not just switch it and see what happens :D Just kidding of course, but I am wondering what limits this to authorized persons?

Steve
 
Re: High voltage pole switch

This is of a similar construction to some Westinghouse 1962 vintage air break switches we have.
Ours are larger though, as they are 69KV class.
BTW, the operating handle is metal instead of wood.
 
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