What overload protection is there upstream of incoming HRC Cutout?

[eveares]

If one's incoming HRC fused cutout was short circuited upstream of the main 60A/80A/100A fuse, is the only other protection the thermal overload on the sub transformer or is there any additional in protection?

Do sub transformers have any direct magnetic based overload protection like MCB's do or is it purely thermal and any possible explosive disconnectors?

Regards: Elliott.

 

[JohnW2]

Do sub transformers have any direct magnetic based overload protection like MCB's do or is it purely thermal and any possible explosive disconnectors?

I have no personal knowledge, but from what people have said here in the past, I think they have fuses, typically around 400A-600A. If that's roughly correct. then, given the 60/80/100A 'supplies' to many houses, if you ever wanted a demonstration that 'diversity works', that's probably it!

Kind Regards, John

 

[Lectrician]

Depends how many feeds are from the sub station. 400-600amp is the most common. These will typically be HRC fuses typically too.

In large cities, it is not uncommon to have no fusing on the outputs :-/ They rely on the HV protection in front of the sub station. Scary.

Smaller hamlets may only have a few homes on small TXs, so 100, 160, 200amp.

 

[Echo the husky]

When my old boss drilled the concentric cable to a domestic cutout, the fuse he took out was 800A according to the DNO bloke.

 

[DaveHerns]

Is this going to be your next "blowing things up" experiment?

 

[Echo the husky]

No way! The bang was incredible when it happened, the loudest noise I've ever heard, and I was in a different room! The bang had an audible mains hum to it. I'm surprised he wasn't injured. The cable he hit was plastered in diagonally in the wall.

 

[JohnW2]

The cable he hit was plastered in diagonally in the wall.

Ah, you mean in a DNO 'safe zone'?

Kind Regards, John

 

[DaveHerns]

Is this going to be your next "blowing things up" experiment?

No, I meant Eveares, he likes blowing things up.

 

[eveares]

Also No!, I tend to stay on the legal and safe side!

 

[Lectrician]

Weighted wet string over HV lines.....That used to be the "done" thing around here. Then someone did it with aluminium tent poles. OMG.

 

[eveares]

Old video, but how cool (and likley scary) it must have been to be near it when it happened.

 

[Echo the husky]

I know, every time I see it I wish I was stood there watching it, that blast was fantastic!

 

[eveares]

Is this going to be your next "blowing things up" experiment?

I have to say, while it's completely off topic; we have recently acquired a pressure cooker. For 1 femtosecond second the idea of putting petrol in it crossed my mind.

 

[aptsys]

I have no personal knowledge, but from what people have said here in the past, I think they have fuses, typically around 400A-600A. If that's roughly correct. then, given the 60/80/100A 'supplies' to many houses, if you ever wanted a demonstration that 'diversity works', that's probably it!

Kind Regards, John

Design load is supposed to be roughly 500W to 1kW per property.

 

[JohnW2]

Design load is supposed to be roughly 500W to 1kW per property.

Indeed (and I think a bit higher when there is electric heating) - and, when one thinks about it, that's not unreasonable as an average over time - 'large' loads (say, >1kW) are usually present for only a small proportion of the 24 hours of a day. However, I presume that there are times of day/year (like the infamous Christmas day morning!) when the average across properties might well get quite a bit higher than that.

Kind Regards, John