trouble shooting underground primary

[4967]

As a troubleman, the company I work for gets calls on underground lines of no power. The dispatchers sent me out to find the cause. I normally work alone. After looking around the riser pole, and finding no cause, the dispatchers will tell me to check existing or to install fault indicators. Please note : I am not told to open /or break the line . Then I'm told to shoot the fuse. My questions are: How safe is this? What does OSHA say about closing in on a 95% or greater chance of the fault? What do other companys do?




















my questio













as a troulb

[Pootnaigle]

Installing fault indicators is no big deal and they should be present in every transformer lokkin at the next transformer in the circuit.. If you get a flag it simply means fault current passed thru the indicator.At some point you will see one indicator with a flag and the next one normal. Your fault lies between these two.And you must always bear in mind that the fault could be a transformer rather than a faulted cable.
The only other method I am aware of is to isolate every transformer . refuse the lateral and start pluging them in one at a time until you blow the lateral fuse again. This process can be quite lengthy and is less than desirable. If you have lots of URD construction I would try and push for fault indicators to be installed at the same time the transformers are put in service..
You didnt mention what primary voltage this was But On voltages of 20 kv and higher I would feel safer with at least 2 men being involved with the actual switching.

[gritter]

For us it all depends on what the riser fed ,Padmount,or under ground development Weather conditions also If its busy theyll ask us to refuse it and give it a "bump" Ear plugs and extendo stick comes out.if she blows back at ya then help comes out Then we start shootin trouble.we'll never open a vault ,pad mounts,or man holes with out help.
We have closed a gang switch in testing for a fault,with help.If it dont feel right dont do it and ask for help
stay safe

[lewy]

As far as I am concerned any time you are trying to find a faulted primary cable it should be a minimum of 2 men. When I first started we would open up half way & try it, but this is very hard on equipment. Now we will Hi-Pot the cables or sometimes use a TDR. When Hi-Poting we will try & have at least 4 men then we can leap frog.

[thrasher]

We will ride out the route of the line and look for a dig-in or someone who has backed into or over a padmount. If we don't see anything then we will try the fuse once just to make sure it didn't blow from a lightning surge or age/load melt it. If it blows then call a second man to bring the TDR out and check the line. BTW we have fault indicators any where the line splits, but not on straight in and out transformers, so that we can tell which section to test. Anywhere we have more than three transformers we install a loop-feed with a normal open point. This way most of the time we can get everyone on and then repair as planned work.

[T-Man]

We'll close into a cable with a suspected fault but we do it from a distance, with extendo sticks, Now that we use fault indicators ( FCI ) we have them on the line to begin with so we can check them first like Poot discribed. We are now installing High Volt LA's on our 14.4 system so lightening will drain off rather than blow a hole on the last open terminator (supposed to anyway) In a loop with an open point we would do the first checks and try the fuse if it went and the FCI's showed the direction of fault then we would isolate, If there were no FCI's we would put them in and try it to find where. If there were none we split the section in half try again if the fuse held we would rectify the remaining cables one at a time till we found the fault. Two men for most of the switching part maybe one man to try the first fuse.

Closing into a fault is something we as Linemen will do wether we want to or not, so every time we go to close a fuse we need to be prepared for the blow. get distance, use current limiters take time to be one step a head of what may happen. Not thinking about a possible blow can get you in a lot of trouble.

Work smart and safe.

[MI-Lineman]

We have trouble shooters do "emergency switching" and even "operational" switching alone. I don't agree but thats our policy. We can usually get help if we want it though. As for fault indicators and hipot adapters, I've had both lie either way. I will say the hipot on our von thumper works very well. We usually isolate at the first switch point and try the riser sometimes with a smaller fuse. If it holds then we put the correct fuse back in and start plugging in sections. I haven't seen a bad tub blow a riser yet as that's what the fuses in the tub are for. I've had guys try to tell me the tub did it but after they change it out and the riser still blows they figure it out!

Underground circuits work just like overhead. The tub's bad....the trnsfrmr fuse will blow(if fused correctly) not the lcp behind it. Although our "BRILLIANT" engineers started drawing up single trnsfrmr spurs with a solid fuse(100amp) at the tub and the actual rated trnsfrmr fuse at the road! It only took a couple of lighting strikes and tub change outs for them to learn!

[Figurehead]

We don't have alot of fci's in our system but will check what's there. Usually the riser's blown so we'll isolate it at the first pot/sectionalizer and close in. Now that primarys available we isolate each succeeding run and use phase sticks with adapters to identify the bad run. Kind of a pain to jump ahead, park, come back and test but it always works and works well. Rarely does someone close into a fault and then it's usually an "oops". Once the bad run is found, park, tag, close the loop up to it and go home. We''ll locate the fault with a VON, and excavate and repair.

[JUS]

4967-
If there are fault indicators, Go to the last flagged indicator. The issue will be between this indicator and the next one. Isolate this span and restore power. Hi-Pot cable.

If there are no indicators, you will have to go to the middle transformer and stand off the out going phases. Shoot it. If it holds, split the remainder and repeat until you find the bad span. Then isolate it and Hi-Pot.

As far as closing in on a fault, wear your PPE and find yourself under your hard hat.

[44kv]

fault indicators are ok we have alot of them but they lie or the last man out there 3am on saturday morn didnt reset the damn things. So we put a 3amp fuse in it and close in the xformers untill we find the bad run and all our underground primary and secondarys are in condut so its just pull one out and pull another in. But all are primary is loop feed so we can get everybody back on and leave it till a reg work day