Safety distance

[cc2]

Hi,

Critical zone from live HV cables,from within human or any other grounded object can trigger arcing, can be estimated by the lenght of insulators given HV system.For 25kV@50 Hz railway that would be about 35 cm.But so called 'safety distance' for humans is considerably larger of course.I wonder if the latter is different for train personell@trained professionals and ordinary people?

 

[driver9000]

Rulebook tells railway staff not go any closer than 9ft to live OLE and that is good enough for me. You are also not permitted to above the cant stripe (orange stripe) on any rail vehicle when under OLE.

OLE must be regarded as LIVE at all times.

 

[cc2]

ok , thanks.
that means the same safety distance holds for everybody in the case of railway.

p.s. and OLE is LIVE most of times.

 

[Craig]

There are instances where you can get closer to the OLE such as on footbridges, but these are obviously suitably earthed and protected from accidental contact.

The OLE should always be considered as live regardless. My dad was on the scene of a rail accident a few years ago where it had been assumed that the OLE has been isolated when it hadn't. Fortunately any serious consequences were avoided.

 

[Mintona]

Yep. 9 foot from the OLE, ladders must be carried horizontally at all times, and it is always to be treated as live.

 

[O L Leigh]

You are permitted to get within 1 metre of the OLE in an emergency situation, but only with strict safeguards. Personally you hope that you never have to.

O L Leigh

 

[P156KWJ]

There are instances where you can get closer to the OLE such as on footbridges, but these are obviously suitably earthed and protected from accidental contact.

The OLE should always be considered as live regardless. My dad was on the scene of a rail accident a few years ago where it had been assumed that the OLE has been isolated when it hadn't. Fortunately any serious consequences were avoided.

assuming things is never a good idea on a railway

 

[cc2]

You are permitted to get within 1 metre of the OLE in an emergency situation, but only with strict safeguards. Personally you hope that you never have to.

O L Leigh

It's at least 1.5 metre from fixed 3 phase 110 kV bus bars.But only in "emergency situations",for trained persons and professionals like HV engineers.That's what I know.For monophase 25 kV railways I dunno.
Any references?

cherio

 

[laseandre]

He works for NX East Anglia.

 

[DaveNewcastle]

. . . ladders must be carried horizontally at all times . . .

Yeah, and best to use non-conductive fibreglass ladders anyway.

assuming things is never a good idea on a railway(

Agreed! Not a good idea, for example, to assume that the "earthed" side of the insulators are, in fact, earthed. They will carry fault currents, (which are likely in wet conditions) and will leave a voltage differential between the apparently earthed side of the insulator and true earth.

I've always believed the 9 foot rule to be excessively cautious, but who said "better safe than sorry"?

. . . and OLE is LIVE most of times.

Yes, and have you seen the cost of an isolation? IIRC it was £4k for a short stretch of the ECML - and that was overnight when not required for traffic!

 

[O L Leigh]

Any references?

Railway Rule Book - Module AC1

Incidentally, I think I should clarify my previous post as it appears that I'm saying you can be closer than 1 metre to the OLE. You can't. 1 metre is the absolute minimum safe distance from live OLE in an emergency situation and you should not allow yourself or anything you are carrying to come closer, nor attempt to rescue a person if any part of them is within this distance.

O L Leigh

 

[TDK]

Railway Rule Book - Module AC1

Incidentally, I think I should clarify my previous post as it appears that I'm saying you can be closer than 1 metre to the OLE. You can't. 1 metre is the absolute minimum safe distance from live OLE in an emergency situation and you should not allow yourself or anything you are carrying to come closer, nor attempt to rescue a person if any part of them is within this distance.

O L Leigh

9 feet (3m) away but 1m below I believe, the only occasion you can venture any closer is in an emergency for rescue purposes only if you deem it is safe to do so.

 

[cc2]

Max 30 cm spark was obtained in this experiment.On usual atmospheric pressure max spark lenght depends on voltage and shape of electrodes.The voltage for closing 30 cm wide gap was 150-160 kV .Note this is DC ,but difference between AC 50 Hz and DC air breakdown is small here .That voltage is much higher than 35..40 kV OLE peak voltage,and I assume something terribly wrong must happen with OLE or below OLE (fire for instance) that will allow spark to jump across say 50 cm.Of course, it's wise not to approach any closer than 1 m.Better safe than sorry

 

[driver9000]

I think I will stick to what the rulebook states, as this is the safe distance set out in the book. To go against the rules is setting yourself up for at the very least 'tea and biscuits' with your boss or at the very worst a day out with an undertaker.

OLE = no touchy touchy!

 

[Ben]

I think this may be a good time to say that, for us passengers, the closest we should be getting is the Platform & should be nowhere closer to it for ANY Reason other than a supervised De-training.

 

[O L Leigh]

I think I will stick to what the rulebook states, as this is the safe distance set out in the book. To go against the rules is setting yourself up for at the very least 'tea and biscuits' with your boss or at the very worst a day out with an undertaker.

OLE = no touchy touchy!

Quite right.

9 feet is the safe distance as stated in the Good Book and should always be adhered to under normal circumstances. However, I was just pointing out that you are permitted to get closer than this in an emergency situation. This isn't going against the rules but applying them correctly as the situation requires.

But even then I don't think I would. Not without getting an emergency isolation first.

O L Leigh

 

[Mintona]

Quite right.

9 feet is the safe distance as stated in the Good Book and should always be adhered to under normal circumstances. However, I was just pointing out that you are permitted to get closer than this in an emergency situation. This isn't going against the rules but applying them correctly as the situation requires.

But even then I don't think I would. Not without getting an emergency isolation first.

O L Leigh

Nope, I wouldn't either, it isn't worth it. Phone call to the ECO, confirm it is switched off before I'd go any nearer.

 

[adambro]

I think this may be a good time to say that, for us passengers, the closest we should be getting is the Platform & should be nowhere closer to it for ANY Reason other than a supervised De-training.

O RLY? :roll:

 

[Ben]

O RLY? :roll:

It was just to educate our younger members. (& any idiotic irresponsible entusiasts who seem to think H&S is a long of rubbish)

 

[AlexS]

Children educating children, how amusing.

Anyone with half a brain knows you don't try and touch grannies' knitting!

 

[GWRtom]

lets not turn this into argument not that it is

 

[TDK]

Nope, I wouldn't either, it isn't worth it. Phone call to the ECO, confirm it is switched off before I'd go any nearer.

Even after an isolation it still is worth waiting until an engineer arrives on the scene as anything in contact with the OHLE will hold a certain amount of electricity, a human body does act as a good capaciter <sp> always use an insulated tool if you need to move anything/one away from any electric current (AC) after an isolation.

 

[O L Leigh]

Quite.

There are three states the OLE can be in. Live, isolated but not earthed and isolated and earthed. Until the OLE has been earthed it can still contain a high residual voltage which is likely to be dangerous to life. When taking an emergency isolation the ECO should tell you which of the three states the OLE is in so that you can proceed accordingly.

Earthing the OLE normally requires a man in a van to attend on site.

O L Leigh

 

[cc2]

Quite right.

9 feet is the safe distance as stated in the Good Book and should always be adhered to under normal circumstances. However, I was just pointing out that you are permitted to get closer than this in an emergency situation. This isn't going against the rules but applying them correctly as the situation requires.

But even then I don't think I would. Not without getting an emergency isolation first.

O L Leigh

Once I was only 3 metres away (~10 feet) from 400 kV power lines. All the time I could clearly sense the presence of E-field,and that feeling wasn't comfortable at all.Althought I was careful,prepeared and well informed what I was allowed to do,and what not ,I wouldn't do it again!
I'm sure it's quite safe 1 m from the OLE IF one knows what he/she is doing.However,if the person is fool than sometimes even 9 feet might not be enough!