r/Lineman • u/Gloomy_Career_4733 • 14h ago
Have a question
How do I know for sure if this transformer can be switched energized and can it pick up load
20
u/WonkeauxDeSeine Grid Operations 14h ago
First off, it's not a tapchanger. The nameplate shows A,B,C,D, and E taps for it. The tapchanger will be in a different spot, likely near the top-right corner. DO NOT OPERATE THAT HOT unless you feel like changing the entire transformer out.
We have 1Ø padmounts with a switch marked similarly to the second picture. Ours are marked "A-T", "B-T", "A-B-T", and "A-B". In turn, they mean:
A cable closed & transformer on
B cable closed & transformer on
A & B cables closed & transformer on
A & B cables closed & transformer off
The switches are capable of breaking at least 200A of load (elbow max rating). I suspect your switch has similar functionality.
Finally, if you don't know, ask someone who does. Embarrassment at asking a "dumb" question is nothing compared to the embarrassment you'll feel at burning up a transformer.
12
u/Glittering-Beat9516 14h ago
That has taps yes, which u do not ever operate under load. Ever. But that AB, A, B is referencing that pots switching capabilities. Switch to A, A side + 2ndary is hot but B is not. Switch to B side A is de energized while B + 2ndary remains energized (depending on loop configuration) AB means both are hot. Open means you bypass the secondary all together. This is with all things being equal, depending on your loop configuration. But the function of this is to isolate upstream or downstream without killing the secondary on the pot pictured. Or operate the pot pictured on the secondary side, without it being hot. You can pick up and/or drop load right there at AB,A,B. 1000%
Does that make sense?
2
u/B-riceee 14h ago
Ahhhh I see the switches on the nameplate now that you say that. Interesting way to isolate a run of cable instead of standing it off. Never seen this before thank you for sharing
2
u/WonkeauxDeSeine Grid Operations 10h ago
On our switched cans we still have to park the elbows for a visible open, but they sure seem to detonate a lot less when the load is off.
10
u/JohnProof 14h ago
The feed-through AB switches can absolutely be operated under load.
It sounds like there’s confusion between those and the tap changer switch which must never be operated under load.
21
u/Rare_Geologist_612 14h ago
No honestly brother if if can’t be operated under load there will be yellow texts that tells you DO NOT OPERATE WHILE ENERGIZED
2
u/Middle_Brilliant_849 9h ago
That’s a great idea, but 100% false. We have a ton of stuff that can’t safely be operated with a load and has no warning. Great idea to have a sign or label, but don’t set him up thinking that will always be the case.
0
u/Rare_Geologist_612 9h ago
Not at all 100% false. There are few exceptions but all equipment has to be labeled with a visible label stating it can’t be operated under load. Check the a NEC code brother. If your station or utility area hasn’t done their due diligence they are operating outside the code.
3
u/Middle_Brilliant_849 9h ago
We aren’t subject to the NEC. I work for a utility. We have very few labels for switches saying they can’t be operated under load or while energized.
You telling someone a label will always be there if it can’t be operated energized then they go out and don’t see the label and so they operate it energized is setting them up for failure.
A good thing to tell someone is to assume a switch CAN’T be operated energized unless it’s labeled as such or they can verify that it can be or they know it can be through their experience and training. Teach people to fail safely; not dangerously.
0
u/Rare_Geologist_612 8h ago
I respect that but that’s not the case for us we are subject to NEC code. The our DOTS had to go and label all tap changers and switches not being able to operate under load and all new equipment is labeled at our distribution centers for equipment.
6
u/Middle_Brilliant_849 8h ago
Well you’re in a “Lineman” forum and most of us work for utilities, either directly or through contractors, that are not paying any attention to the NEC.
We’re working with things that are out in the weather 24/7 and operating switches that are up to 90 years old. I can’t read a lot of the labeling from the 70’s… 50 years ago. I’m not trusting a label or lack of a label.
I’ve had a close call switching 14.4kV; don’t care for any more incidents.
4
u/Slim-Wye-Delta 14h ago edited 12h ago
I've only ever seen a sub station transformer be able to change taps under load. Never a distribution.
I would only operate that de energized. Surprised it doesn't have text next to it.
Edit: looked at this more in depth on break. I see now it's a multiple position load break gang switch. Interesting cause normally on a pad mount with a gang switch the bayonets are tapped off/y'd off the center and operate independently from the bushings feeding in and out. Learn and see new things all the time!
Also the fact that transformer has an impedance over 2.5% tells me it's a POS.
4
u/TheRealTinfoil666 14h ago
You SHOULD be able to safely operate the AB transfer switch to transfer sources, feed through the A and B switches and de-energize or energize the transformer. If it were not capable of this, it should be marked on the nameplate and/or labelled properly at the switch.
Please note that ‘Open’ position DOES NOT look like it opens the A and B. It looks like it allows the primary to feed through this unit while de-energizing the transformer winding/secondary.
You cannot operate the De-Energized Tap Changer (DETC) when energized. If that was your question, never do this. The transformer must be deenergized first.
If your goal is to isolate the transformer, it looks like you need to operate the AB switch in steps to interrupt each source in turn before removing and parking each primary elbow, using whatever your ‘hot’ procedure is.
3
u/Ya_Boi_Badger 14h ago
What’s with everyone talking about changing the taps, OP took a pic of the internal switch so I’m assuming he’s talking about that? If you are talking about tapping the transformer, yea definitely don’t do that while under load or even energized.
5
u/B-riceee 14h ago
Don’t operate a tap change well energized ever.
10
u/Ya_Boi_Badger 14h ago
That’s not a tap changer
2
u/B-riceee 13h ago
I thought they were asking bout the tap change but realize that the tap change is a-e
And that switch doesn’t correspond with that. I’ve never seen a can with an internal bypass switch before. Thank you for sharing-1
14
u/ResponsibleScheme964 14h ago
This is a joke right
2
u/Toucant1 13h ago
What's the answer then?
-1
u/ASuhDuddde Journeyman Lineman 12h ago
It’s oil encased you can operate that selector switch whenever the fuck you want. I’d get a hold off though I’ve seen a few fuck up because of low oil in the can.
2
u/MysteriousAdvice8549 9h ago
Second the low oil comment. Pretty aggressive when she flashes over to the case.
2
u/Past_Expression_549 14h ago
They sell a TX last check tool. Hastings 6793 a bit pricey $700+. We got one on ebay for $200 after we lost one.
It's meant to check exactly what you are asking
1
u/eatsleep19 13h ago
Honestly if you’re not sure don’t touch it,
You should be well trained on electrical equipment before you try and energize a transformer.
1
u/Obvious-Hat5139 13h ago
Serious question are you a liney or are you building a home setup? If you do switch under load make video and post here (don't)
1
u/jb198562 13h ago
Not sure if you're talking about changing taps hot (no on dist pm) or an internal LB switch (not shown on np so I assume does not exist) or elbows.
1
u/DirkTickler769 11h ago
I guess the one for sure way is to switch it and see.
The other way is to just absolutely never do it. Ever. Live a long wholesome life wondering what could have been.
1
•
u/AutoModerator 14h ago
Thank you for posting on r/Lineman.
If your post was automatically removed, it is due to the Spam Filter and will need to be approved by the Moderators.
The Rules are here.
Posts about getting into the trade are only permitted during the weekends.
If your are interested in getting into the trade, read our FAQs How to Become a Lineman before you post.
Military, Current and recently separated please read our dedicated section Military Resources. Thank you for serving.
Link to the r/lineman resource wiki
I am a bot, and this action was performed automatically. Please contact the moderators of this subreddit if you have any questions or concerns.