Todays Job

[Highway Man]

Cars don’t crash into domestic CU’s. How often do cars - or their occupiers- that crash into lighting columns get electrocuted?

very few, you are sat in a faraday cage in a car.

 

[Munroast]

No the national grid is 500A which is what the mains is for the lights. The actual lights are fused down to 6A, If a car knocks them down as they do quite frequently, the actual mains cable will still be live, it would be rare for the main substation fuse (500A) to blow. It is the same with your house, you have a 500A main incommer fused down to 100A or 60A in your cutout. You might blow the 100A fuse but you wont blow the substation fuse.

could you make a steel lamp post live ? since its pretty well earthed

 

[Highway Man]

could you make a steel lamp post live ? since its pretty well earthed

yes you can have a live lamp post, it is quite a common occurance

 

[Munroast]

anyway - progression with the bog seat

Its more toilet seat shape now

and I have started the lid, didnt go too well, didn't check the planer was at 90 degrees, probably just out by a degree, but glue all six together and it would be a bit bowed, sort out the angles on Monday

 

[Highway Man]

Looking great. Well done, hope you remember to sand it down well. lol

 

[MNW67]

yes you can have a live lamp post, it is quite a common occurance

Sounds dangerous. But I know nothing about electrics. Would it kill somebody?

 

[Highway Man]

Sounds dangerous. But I know nothing about electrics. Would it kill somebody?

yes very easily, we have special ppe to protect us from receiving a shock when we deal with such situations.

 

[Jurassicspark]

Sounds dangerous. But I know nothing about electrics. Would it kill somebody?

Yes and no.

The lights will be earthed to ensure any fault currents doesn't stray on any part of the metal body. PEN fault detection will be there too.

Failing that, RCD or some other typr of device is your friend.

 

[Munroast]

yes very easily, we have special ppe to protect us from receiving a shock when we deal with such situations.

but are they not well earthed by virtue of being concreted into the earth ?
or would the flow to earth never be high enough to trip the 500a fuse

500A is a lot, 240v ? if so 120,000 watts (40 kettles)

 

[Highway Man]

Yes and no.

The lights will be earthed to ensure any fault currents doesn't stray on any part of the metal body. PEN fault detection will be there too.

Failing that, RCD or some other typr of device is your friend.

We dont have RCD in street lighting, the earths regularly disconnect either by rotting or breaking off, in the event of a car colliding into them the first to be ripped out is the earth.

 

[Highway Man]

but are they not well earthed by virtue of being concreted into the earth ?
or would the flow to earth never be high enough to trip the 500a fuse

500A is a lot, 240v ? if so 120,000 watts (40 kettles)

No earths are in the street lights as far as an earth goes, they are fed purely as Live and Neutral direct off the grid. The earth that we put in is purely to turn it into a PME supply but a lot of the time this is fine under normal conditions, however when a car hits the post they are ripped out of the ground leaving just a live and neutral wire. They just sit there fizzing.

 

[Highway Man]

We do have private networks which are fed via a similar thing to a house where we will use RCD's in the consumer units which gives a much safer supply than the normal straight off the grid feeds. Once again you have the problem that the feeds to the consumer units are straight off the grid and we do have cars and lorrys hitting these feeder pillars too.

 

[Highway Man]

called out last weekend to one, this column was live. You can clearly see the earth has been ripped out and lying next to the column

 

[Jurassicspark]

No earths are in the street lights as far as an earth goes, they are fed purely as Live and Neutral direct off the grid.

As you would know, a 10mm bonding conductor is usually connected to the MET just inside the door opening. Surelyt the 'bond' is there to negate any difference in potential between the DNO earth and the column in the ground under fault conditions.

 

[Highway Man]

How ee deal with them, then simply get a new post put in and reconnect it.