Blown Transformer Cutout

[mivey]

It’s always possible if someone’s life is at risk.
If it’s a choice between your convenience and my safety, you’re going to lose every time.

yep. If the crew feels unsafe, I will drop it no questions asked. The critical loads will get a call beforehand if time permits. Closing cutouts is a matter of seconds. For speed, we will sometimes have 3 sticks hooked and ready to go.

I express to our crew leaders they control the site and assure them I will back their decisions. Any crew member has the right to refuse to do anything they don't feel trained to handle or that puts them at abnormal risk. It is no place for bravado.

 

[mivey]

Try telling that to linemen/companies who just send it in. Remember those leaning poles we spoke about?

I will, and do.

 

[mbrooke]

I will, and do.

Do they listen?

"send it in brother!"

 

[mbrooke]

yep. If the crew feels unsafe, I will drop it no questions asked. The critical loads will get a call beforehand if time permits. Closing cutouts is a matter of seconds. For speed, we will sometimes have 3 sticks hooked and ready to go.

I express to our crew leaders they control the site and assure them I will back their decisions. Any crew member has the right to refuse to do anything they don't feel trained to handle or that puts them at abnormal risk. It is no place for bravado.

The POCO that serves me never drops load to close in a cutout.

I've heard some linemen say that if a CLF, k-mate or companion is present the lid won't blow off? How many amps does it take to blow a lid off with a K or T link expulsion fuse?

 

[Hv&Lv]

The POCO that serves me never drops load to close in a cutout.

Neither do we.
Mivey doesn’t either...

go back to his post #17, third paragraph for context.

 

[mivey]

Do they listen?

Of course.

 

[mbrooke]

Neither do we.
Mivey doesn’t either...

go back to his post #17, third paragraph for context.

W

e look for indicators like dead animals, burnt limbs, damaged equipment, etc. Many times the dead animal may disappear (easy meal for some other critter) or just be hard to find.

Missing indicators will result in a try-it fusing of small units. No short sticks for this. PPE isn't bullet proof. Hiding in the bucket can help but oof. Larger units will be tested on site or swapped out for testing in shop.

I will drop a circuit with an automated recloser, breaker, or gang switch before putting someone at abnormal risk.

30 ft is about my limit on hot-stick fusing. The swaying is too much and my eyesight is not what it used to be nor is my steadiness.

So PPE not being bullet proof isn't abnormal risk?

 

[mivey]

I've heard some linemen say that if a CLF, k-mate or companion is present the lid won't blow off? How many amps does it take to blow a lid off with a K or T link expulsion fuse?

A CLF can drastically reduce the energy. 1/4 cycle vs several cycles is huge.

The amps needed will depend on the transformer size and type and the fault clearing time. You can run the numbers but I would at least consider putting a CLF wherever the SCC is about 4000 amps or greater.

Consider that smaller units (say 15 kVA) can handle an I^2T of 500,000 A^2s and larger units (like 5000 kVA+) can handle 1 or 2 million A^2s. Run the withstands against the fault and clearing times for the recommended fuses and you can build a table of fault levels for each transformer that will trigger the use of a CLF.

 

[mivey]

W


So PPE not being bullet proof isn't abnormal risk?

The job is risky by nature. Nothing is 100% safe. It is up to the crew to determine if they feel they are operating within the capabilities of their training. If they are not, then they need to change the situation.

 

[paulengr]

Abnormal is when you run into a situation where you see something abnormal. Like cracks in the pole, lag bolts pulled through, burn marks, fluid leaking somewhere it shouldn’t, cracked or blown insulators, voltage indicators giving strange results. Anything that’s not normal and could be a sign of other issues. OSHA gives a list in .269.

There are two different situations with PPE and really any equipment. Normally PPE should be backup/secondary protection like wearing FR PPE...arc flash is rare. Hopefully it’s not one of those days. The PPE is backup protection.

That’s different from rubber glove live line work where there is no backup or extra layer of protection. Like putting on a saddle or a jumper or a hot line clamp directly onto a line without a stick. There is no fail safe.

 

[mbrooke]

The job is risky by nature. Nothing is 100% safe. It is up to the crew to determine if they feel they are operating within the capabilities of their training. If they are not, then they need to change the situation.

Alright. But how do you know that a 15-50kva transfomer will not blow its lid with scalding hot oil going all over the place when the fuse is thrown in?

 

[mbrooke]

Abnormal is when you run into a situation where you see something abnormal. Like cracks in the pole, lag bolts pulled through, burn marks, fluid leaking somewhere it shouldn’t, cracked or blown insulators, voltage indicators giving strange results. Anything that’s not normal and could be a sign of other issues. OSHA gives a list in .269.

There are two different situations with PPE and really any equipment. Normally PPE should be backup/secondary protection like wearing FR PPE...arc flash is rare. Hopefully it’s not one of those days. The PPE is backup protection.

That’s different from rubber glove live line work where there is no backup or extra layer of protection. Like putting on a saddle or a jumper or a hot line clamp directly onto a line without a stick. There is no fail safe.

How well do insulated buckets protect you if a glove fails during hot line work?

 

[mbrooke]

A CLF can drastically reduce the energy. 1/4 cycle vs several cycles is huge.

The amps needed will depend on the transformer size and type and the fault clearing time. You can run the numbers but I would at least consider putting a CLF wherever the SCC is about 4000 amps or greater.

Consider that smaller units (say 15 kVA) can handle an I^2T of 500,000 A^2s and larger units (like 5000 kVA+) can handle 1 or 2 million A^2s. Run the withstands against the fault and clearing times for the recommended fuses and you can build a table of fault levels for each transformer that will trigger the use of a CLF.

Basically close to the substation. I know of POCOs who use companion IIs on all pole pigs.

Why are you more likely to test larger units?

 

[Hv&Lv]

How well do insulated buckets protect you if a glove fails during hot line work?

Very well as long as they are maintained. Our liners and trucks are dielectric tested every year
Gloves changed and tested every thirty days

 

[mbrooke]

Very well as long as they are maintained. Our liners and trucks are dielectric tested every year
Gloves changed and tested every thirty days

How bad is a shock from bad glove in a tested bucket?

 

[Hv&Lv]

Basically close to the substation. I know of POCOs who use companion IIs on all pole pigs.

Why are you more likely to test larger units?

Cost. You have to weigh the cost of the unit vs time to test.
EVERY XF above a 1500 including station transformers, are tested with TTR and inspected should a station breaker or fuse blow.

 

[Hv&Lv]

How bad is a shock from bad glove in a tested bucket?

I can tell you this. If it’s very damp or misty outside, 14,400 volts absolutely hurts even with gloves and a good bucket..

On a dry day none. But it isn’t a “shock” like your thinking.
experience is first and foremost. Knowing what and when to touch is key.
Gloves, sleeves, etc are primary protection. Tested bucket is secondary.

years ago we used to glove 7200 off a set of hooks standing on a pole.

 

[mbrooke]

I can tell you this. If it’s very damp or misty outside, 14,400 volts absolutely hurts even with gloves and a good bucket..

Line to line or line to neutral?

On a dry day none. But it isn’t a “shock” like your thinking.
experience is first and foremost. Knowing what and when to touch is key.
Gloves, sleeves, etc are primary protection. Tested bucket is secondary.

Make sense.

years ago we used to glove 7200 off a set of hooks standing on a pole.

I remember years back young guys had to pole dance before they had the privilege to use a bucket.

 

[mbrooke]

Cost. You have to weigh the cost of the unit vs time to test.
EVERY XF above a 1500 including station transformers, are tested with TTR and inspected should a station breaker or fuse blow.

Good advice! Station is an obvious test.

 

[mivey]

Alright. But how do you know that a 15-50kva transfomer will not blow its lid with scalding hot oil going all over the place when the fuse is thrown in?

You don't. There are no absolutes. It is risk management.