Blown "fuse" in transmission line (pictures) 2

[OpticControl]

Question,

Yesterday I was disturbed by a really loud explosion in our back yard and electricity went out.
When I turned to the window I saw sparks falling down our backyard so I immediately new there was a problem on the transmission lines.

I took a picture of what seems to be a fuse disconnect connection on the transmission line.

CenterPoint came and (I believe) replaced the "blown fuse" with a new one and closed the connection. Power came back immediately.

I am interested in knowing the proper terminology for this disconnect and what kind of protective device is it?

If anyone knows please let me know.

Best regards.

 

[bacon4life]

That is a distribution fused cutout. Here are some links explaining how they work and the video shows the actual fuse element inside the cutout:

https://en.wikipedia.org/wiki/Fuse_cutout

https://www.youtube.com/watch?v=GFd30p4TJ8E

Typically utility folks refer to voltages above 69,000 volts as transmission versus voltages below 35,000 volts as distribution. From the length of insulators, my guess this distribution circuit is around 25,000 volts (25 kV).

 

[itsmoked]

I think they're also called "drop-outs" too because once blown they drop down making them easier to find.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[cuky2000]

Cut-out rated for 25 kV is a good guess. Line post insulator may be rated for 34.5 kV but could be operated at lower voltage. (see below)

 

[wbd]

This cut-out is feeding a riser cable going to a pad mount transformer. Since the cut-out fuse blew and the cut out fuse holder fell open as it is designed to do, this would obviously indicate a fault. Therefore, I am surprised that the utility lineman just re-fused the cutout and closed it back in. As you probably realized, the cut out makes a very loud noise when it blows.

Therefore, the linemen should have inspected the padmount and meggered the cable to verify no fault. Of course, they may have found a squirrel still smoking at the base of the pole and determined that was the cause.

 

[unclebob]

The top picture isn't clear, but something dead seems to be hanging near the LA. Another zapped critter...

 

[cuky2000]

Appear to be a wildlife cover protection

 

[cranky108]

look again between the two pictures, there is a difference in that something is in the top picture that is not in the bottom picture.
Fuses can also blow for an overload. Have seen that many times recently. A number of new hot tubs, or a pot grow move in and we start seeing fuses blow. The next thing is we up size the pad mount.

Also seen fuses blow, flowed by high demand complaints at car washes. Mostly from starting several motors at the sametime.

 

[jghrist]

What is different between the two pictures is that the top picture was taken while the cutout was open. The "something dead" is the cutout tube hanging open.

 

[cranky108]

No there seems to be something just below the arrester.

 

[stevenal]

Here's the other difference in the first picture. I would say it's the remains of the arrester housing following a failure.

 

[jghrist]

I would say it's the remains of the arrester housing following a failure.

I agree. Actually it seems like two separate parts of the housing ended up missing, the middle and the bottom. The arrester was not replaced in the second picture, but service restored with the ground lead disconnector operated. What I initially thought was a squirrel guard on the top (darker color) now seems like a burnt portion of the housing.

 

[bacon4life]

The picture does like a damaged surge arrestor housing. The loose ground wire is also indicative of a failed surge arrestor being disconnected by a small explosive charge. The graphic below is from an article explaining how arrestor work.

https://www.inmr.com/disconnector-reliability-sentinel-word-life-arrester/

 

[cranky108]

Now you are making me think, what is in the arrester that would stay intact after an operation?
I would think the blocks would come apart.

If this was a big event I would understand, refuse and move on. But if this were just a random failure, why would the serviceman not replace the arrester?

Expect another outage, by someone else, to replace the arrester.

 

[stevenal]

It's not intact, the ground wire is missing.
No arrester on the truck, and customers want the juice back on. Restore power and report the failure for a scheduled outage.

 

[Palletjack]

A lot of the polymer arrestors will not simply blow the bottom disconnector as the picture above shows. They will take some smaller shots and separate at different points anywhere on the arrest or. I see them with the tops blown off, blown in half, etc..

And late at night, it’s a simple matter to push it up out of the way and throw the fuse back in. Work on replacing it on regular time during the daylight hours.

 

[bacon4life]

An arrestor can often later be replaced without an outage using hot sticks. It is common for a trouble crew to make a temporary fix and have fully equipped crew to return during the day to make permanent repairs.

 

[Palletjack]

An arrestor can often later be replaced without an outage using hot sticks. It is common for a trouble crew to make a temporary fix and have fully equipped crew to return during the day to make permanent repairs.

The arrestors like that are removed and replaced by hand and put back online with a hotline clamp by a shotgun stick.

 

[jghrist]

The arrestors like that are removed and replaced by hand and put back online with a hotline clamp by a shotgun stick.

Putting the arrester back on line depends on the installation. From the photo, it looks like both the connection from the cutout to the arrester and from the cable terminator to the arrester are made by separate wires connected to the top of the arrester. with this arrangement, the arrester cannot be replaced without disconnecting the cable terminator. If there were one wire from the cutout to the terminator, the arrester could be connected to this wire with a separate wire and a hotline clamp. Then, the replacement could be made without disconnecting the terminator.

 

[Palletjack]

Putting the arrester back on line depends on the installation. From the photo, it looks like both the connection from the cutout to the arrester and from the cable terminator to the arrester are made by separate wires connected to the top of the arrester. with this arrangement, the arrester cannot be replaced without disconnecting the cable terminator. If there were one wire from the cutout to the terminator, the arrester could be connected to this wire with a separate wire and a hotline clamp. Then, the replacement could be made without disconnecting the terminator.

I did line work for 20 years before I finished my degree (LOTS of nights). Yes, I started late in the engineering field, but still with the same utility company. So close to retirement I can taste it…
We would install these with one wire and simply bend the wire and single wrap around the top of the arrestor stud. If it’s a one or two customer tap we would definitely pull the fuse during the day and replace the arrestor dead. For a tap feeding something like a neighborhood we didn’t want to take out of service, the single wire with a bend simply lifts off the top stud.

Using two separate wires is crazy and won’t stay put easily enough to tighten the little 3/4” square washer on the arrestor.

Raise the wire out of the way and replace the arrestor. Next, back the bucket away and taking the shotgun stick, push the hot wire to the top of the arrestor to make sure it holds. I’ve had brand new arrestors blow or blow the fuse when they are energized.
After a few seconds, bring the bucket back to position and install the wire on the stud and tighten the nut on the washer. Don’t forget to replace the animal guard. Done…