A Day With A Lineman #7 ~ Testing, Locating, and Repairing High Voltage Underground Cables

in #adaywithalineman3 months ago

What is happening my fellow Hivers? I hope everyone is happy, healthy, and enjoying Life. Getting a phone call at 2 am to go to work doesn’t seem too enjoyable but you gotta make that lemonade with those lemons. You know what I am saying? When this call came in and they told me where the outage was at I thought, “Oh Great!!! This is going to be a nightmare!” (since it was early in the morning does it make it a morning-mare?) This area has a lot of old high voltage underground cable that goes all over the place. Across people’s backyards, under trees and driveways, it’s a frickin’ maze!! Not to mention the pad mounted transformers are often hidden in some sort of thorny bush in the back corner of someone’s yard. I often wonder what they were thinking when they installed this stuff 20-30 years ago. Oh well, time to lace up the boots and see what this early morning outage has in store.

On our mapping software I could see that there were 2 runs of underground coming off of one pole. That pole also had a transformer on it. So the overhead feed comes from a fused cutout across the street. Overhead lines energized at 7,200 volts carry the power across the street to this pole. From there the primary underground goes in 2 directions. Let’s just hope there is an easy way to sectionalize these cables to test them and see which one is bad.

Upon arrival, no such luck! This pole is an absolute cluster beep!! No is easy way to separate the 2 underground feeds to see which feed is causing the problem. Who knows it could be the transformer on the pole that blew the fuse across the street or one of the 3 transformers on cable or one of the 5 transformers on the other... or any piece of cable in between those transformers... or the service wires going to one of the dozen or so houses... Good grief this is gonna be a pain in the yoo-hoo

A Day With A Lineman #7


Testing, Locating, and Repairing High Voltage Underground Cable

As much as I try not to focus on why on God’s green earth someone would build a pole like this, it is still frustrating non the less. That is besides the point, we need to separate these 2 runs of cable and fuse each run. This will allow the transformer to be separate from the 2 underground runs of cable and also allow us to test each of them individually. Plus it will make it easier if we have outages in this area in the future. Taking a 1/2 hour now to install fused cutouts will save us a bunch of time finding and inspecting all these transformers.


After installing the fused cutouts and re-fusing the blown fuse across the street, we energized the transformer on the pole and checked voltage. Welp, that isn’t the problem. Now I guess we get into the fun part... testing each run of cable with a fuse to see which run has the fault. By this time it is around 4 am and we called one more guy in to give us a hand and he just showed up. It’s time to see some Lineman Fireworks and hopefully not wake the neighborhood. If you haven’t seen the video I made a couple days ago, go check it out Here

We found out really quick which run of underground had the fault. The first fuse we closed in blew and it sounded like a couple shotguns going off at the same time. It blew the 8 amp fuse at the pole and the 15 amp fuse across the street.


The quality isn’t too good due to the sun not being up yet but I was able to stop the video and grab a still shot of the fuse blowing.


So we isolated that run of cable from the overhead line and re-fused the cutout across the street, then energized the transformer again. Then closed in the fuse to energize the other run of cable. Thank God that One didn’t blow too or we would have had a bigger problem on our hands.


With the bad cable/transformer isolated from the overhead line it’s time to go to each transformer and do some testing. The first thing we do is test for voltage and ground the cable. This proves that the cable is truly de-energized and it is safe to work on. Since it is underground and we can’t see where it goes. We have to prove that we are on the right cable. Many electrical accidents and even deaths have happened on underground cables, not to mention many limbs have had to be removed due to being cooked from the inside out. So we take extra extra precaution, double and triple check everything.

At each transformer we visually inspect and smell for any type of burning smell. I always open the pressure relief valve and smell the air coming out. If we smell burnt oil it’s a sure sign the transformer is bad. They all seem to check out OK in our book so next it testing the cable. We actually check the transformer and cable at each location at the same time. We have to bounce back and forth a bit but that is just how it needs to be done.

To test for bad cable we use what is called a Hipotter. Basically it puts high voltage into the cable and testS the insulation without causing further damage. It’s probably a lot more scientific than that but Lineman keep things simple. So the Hipot tester we recently got uses a Milwaukee battery and attaches to a hot-stick. I didn’t get any photos of it in action but this is what it looks like.


Without this we would be isolating sections of cable and testing with a fuse. Fuse Bangin’ is not fun and it is not the best for anything on that section of line. All the fault current is spread throughout everything hooked to that section of line. Plus the customers lights would be going On and Off over and over again. Not to mention the whole neighborhood would be woken up to what sounds like shotgun blasts.

Lucky for us the first section of cable from the pole to the first transformer is what tested bad. The majority of the cable runs along the road and not in anyone’s nice grass yard. The moment we found out that the transformers were good we called in another guy to bring in the Thumper, the cable had to be bad somewhere. Using the Thumper is how we actually pin point the bad spot in the cable. But first we need to call in an Emergency locate before we can do any digging. This notifies all the utilities in the area to come and mark any of their underground facilities in the area. Water, sewer, gas, phone, cable tv, fiber optic, and electrical. From the time the emergency locate ticket is created they all have 2 hours to get their stuff marked and we have 2 hours before we can dig.

First thing we need to do is locate the route of the cable. It never goes in the direction you would think it would go. Zig-zagging all over the place. So while one of us was busy marking the location of the cable the other 2 guys went to the local service center and picked up some cable and splice kits to make the necessary repairs.

After verifying we didn’t have any other bad runs of cable with the Hipotter, the Thumper arrived. Now let’s hook up the Thumper and get out Thump on. C’mon!!


What this machine basically does is apply voltage to the cable until faults. You can watch the meter build volts then pop is bleeds off. Once you get it thumpin’ at a steady pace you follow your locate marks and listen for the beat of the Thumper. It will get louder and louder. Now in order to narrow it down you turn the Thumper down a bit. This quiets the thumps and slows down the time between thumps. Then grab a road cone or a shovel and put it to the ground and place your ear on the other side. It’s like an Indian Tracking Technique. Wherever you hear the thumps the loudest is dang close to the faulted cable. Within 2-4 feet I would say.


I am telling you the timing of this whole operation was working out pretty good. By the time the mini excavator got there we had located where the fault is and within 15 minutes we had the okay to start digging.


We need to make the hole big enough to crawl into and have room to work. Plus we need to be careful not to damage the cable any more than it is. It should be about 4 feet deep but with this direct buried cable who knows. You see back in the day, they just dug a ditch, threw the cable in and buried it. No conduit. Just straight in the ground. After scrapping little by little we found a small glimpse of the cable and one of us jumped in and exposed it and mark it by leaving a shovel next to it. That way the operator always had a reference to where it is.


Once we got about 6-8 feet of the cable exposed it was time to look it over and find that dang bad spot. When doing this in the past the bad spot is pretty easy to find. “Gee there it is!” The cable is normally blown partially or totally in half. This time we searched and searched and found nothing. The outer concentric (ground wires) weren’t broke or melted... where in the heck is the bad spot. Welp, fire up the Thumper and let’s make sure the bad spot is on the exposed cable.

Everyone Outta the Hole!
4032849378C74028804C37F18AC6D9B3.gifslowed 4X

It happened so quick we couldn’t tell where it came from. Time to turn to technology once again. I took the video from my phone and slowly went through the video frame by frame. Then Ta-Da there is was.


Now we know exactly where to look. The bad spot must be tiny since we couldn’t see it on the first inspection. So I dove on in and took a look in the area of the flash. Welp, there is the pin-hole


Alright, now let’s get this cable repaired and get the power back on before this heat hits. It’s suppose to be over 100F and at the moment it was really humid and about 80-85F.

First, cut out the small bad spot, pull back the concentric ground wires, remove the insulation exposing the conductor, then slide the waterproof end of the splice over the cable. Next, press on the splice connector to the conductor and peel off some of the semi-conductive layer (Pain in the A$$) and wait for my buddy Cheez-it to finish up his side.


Sliding the main body of the splice and end caps over the cable is a power struggle for sure. The cable is flimsy and wants to bend. The splice body and caps have to be super tight because that is what keeps all the moisture and dirt out of the splice.


It Puts The Splatts In the Hole!!


With the splice muscled together, all that is left is to connect the concentric ground wires using a piece of #6 solid copper. Then this splice is done and read to energize... we hope.


Now before we go backfilling the hole and wrapping this thing up we energize it to make sure everything in the hole is good to go. Wouldn’t that suck to bury it and have another bad spot in the same place you just dug or for some weird reason your splice doesn’t hold?!? Then you have to go and do it all up again.

Give it a Dab For Good Luck


The lights are back on and all is well and good once again in Burbank, WA. It was close to 11 am when the power was restored and the heat was just starting to hit. Perfect timing once again. Dang we are good :wink:wink Now all that is left is to backfill the hole and clean the area up and make it look like we weren’t even there. Like an old Foreman once told me, “When you are working on someone’s property, leave the place looking better than when you showed up.


Thanks for droppin’ in and checking out another edition of *A Day With A Lineman”. It was a little lengthy but that is just how it is sometimes.

Hopefully this shines some light on the whole idea that we just flip switches to get the lights back on. Some people get really impatient and angry when their power has been out for 45 minutes... Because they just flat out don’t have any idea what it takes to find and make repairs. So be nice to your local Lineman, remember you could be the last one to get your lights and A/C back on if you are an A-hole. :wink:wink

Until Next Time...

Hive On
Thanks to our Union Contract
I get the rest of the day off...


See, I didn't even know there is an underground portion to the everyday pole.

Look at that you learned something today, now you can do nothing the rest of the day. Except those certifications deleos you got. 😉😉

I have a guy that when a customer asks him what’s going on, he talks to them like he would another Lineman. They just look at him like WTF?!?!....

Do you not have problems with the concentric ground wires and copper being different alloys? You did not show the ground splice work.

No, the concentric wires are copper just coated with.... dang it I can't remember. The ground splice is just a simple side by side press connector with anti-oxidation goop in them. Nothing fancy. This area is the desert and is drier than a popcorn fart. Lol

This whole area of the system is getting rebuilt, one street at a time. Now days the concentric wires are covered by a hard plastic protective jacket. So the cable has another layer on it. Conductor, thin semi- conductive layer, insulation, thin semi-conductive layer, concentric wires and then outer jacket.

More protection, but more work to splice. You mention conduit, does the new underground stuff get put in conduit?

Yes, all of our underground gets put in conduit. Helps it last longer and adds another layer of protection just incase someone digs into it. Also we can install all the conduits in the early stages of a subdivision being built. Then pull our cable in when we need to. Also helps with heat distribution, which typically is a non issue.

Congratulations @jlsplatts! You received a personal badge!

You powered-up at least 100 HP on Hive Power Up Day!
May the Hive Power be with you!

You can view your badges on your board And compare to others on the Ranking

Do not miss the last post from @hivebuzz:

Hive Power Up Day - Let's grow together!
The HiveBuzz Shop - New Items and Designs