Loss of power

[modernrail]

So this is a new one for me. On the 14.29 out of Euston to Glasgow. Stopped almost immediately on climb out of Euston due to a loss of power. Lost lighting and air conditioning.

A few minutes later the train manager told us there was an overhead line problem and driver was on the control expecting it to be sorted in a few minutes. Then power was restored and we are on our way.

Seems like an odd one. What might have happened there I wonder?

 

[Sleepy]

Can be the supply from National Grid cut out for some reason briefly. Or a tree branch touching overheads in windy conditions.

 

[Elecman]

Circuit breaker tripped and the Electric Control Room Controller needed to allow time for any emergency reports ( a few minutes ) before attempting to reclose the breaker

 

[Mcr Warrior]

Circuit breaker tripped and the Electric Control Room Controller needed to allow time for any emergency reports ( a few minutes ) before attempting to reclose the breaker

Is that what actually happened, or the most likely cause?

 

[Elecman]

No idea but most likely if you were only stopped for a short length of time

 

[Bletchleyite]

It's decidedly windy out at the moment so lots of possible causes eg something briefly tied up in the OHLE?

 

[Tilting007]

Is that what actually happened, or the most likely cause?

Yes, OLE tripped. Reset without issue.

 

[modernrail]

Yes, OLE tripped. Reset without issue.

How often does that sort of thing happen? Is the cause usually some sort of unabated surge that sneaks though whatever the safeguards are?

Could it also trip things on the train?We noticed the power sockets went and the guard reset them.

 

[Elecman]

How often does that sort of thing happen? Is the cause usually some sort of unabated surge that sneaks though whatever the safeguards are?

Could it also trip things on the train?We noticed the power sockets went and the guard reset them.

Quick outages are mostly due to birds frying themselves tree branches of other detritus blowing in the wind onto the OLE or very occasionally train fault prior to the train 25kV Main circuit breaker. I’ve never known a complete loss of Grid Supply that only lasts for a few minutes as refeeding arrangements take some time to carry out

 

[occone]

What kind of battery backup for auxiliaries do electric trains have? And how long will things like toilets, lights, and heating work for without overhead power?

 

[Bald Rick]

How often does that sort of thing happen? Is the cause usually some sort of unabated surge that sneaks though whatever the safeguards are?

The OLE trips, somewhere on the network, several times a day. Three things are the main causes:

1) problem with the train
2) wind blowing something into contact with the OLE
3) nobody knows.

It’s not an ‘unabated surge’ but the monitoring systems detecting a short circuit somewhere.

 

[Crossover]

What kind of battery backup for auxiliaries do electric trains have? And how long will things like toilets, lights, and heating work for without overhead power?

HVAC (Heating, Ventilation, Air Conditioning) will almost certainly stop as soon as power is lost - I am fairly sure that even through neural sections when the breakers open, the HVAC ceases for a while (indicated by the drop of noise)

For lighting there would be a point where it would drop to emergency lighting levels but I don't know what runtime would be expected of the full lighting/toilets after power has dropped and the train is running on the aux batteries

 

[Archvile]

What kind of battery backup for auxiliaries do electric trains have? And how long will things like toilets, lights, and heating work for without overhead power?

Pendo's auxiliaries will run for ~ 30 mins - 2 hours depending on whether pantograph is up or down (if left up, will discharge back to the OLE and run down quicker), condition of batteries, outside temperature etc.

 

[mike57]

if left up, will discharge back to the OLE and run down quicker

I find this strange, as this means that the train is energising the OLE, and I would have thought that would be a big no no on safety grounds. Very much the same issue as if you have a backup generator and dont isolate the incoming supply.

 

[trainmania100]

Few years ago similar problem on approach to Blackfriars in a 387. Driver stopped on a gap in the third rail and had to roll back

 

[Falcon1200]

How often does that sort of thing happen? Is the cause usually some sort of unabated surge that sneaks though whatever the safeguards are?

As @Bald Rick says, all the time! The Electrical Control Room (ECR) will wait for the specified time, IIRC 2 minutes, and if no adverse reports have been received, will re-energise; But if the overheads trip out twice more the power will not be restored until they have been checked. If the overheads trip and fail to reset, they are down, or at least damaged or compromised somewhere. That is when the fun starts!

 

[Archvile]

I find this strange, as this means that the train is energising the OLE, and I would have thought that would be a big no no on safety grounds. Very much the same issue as if you have a backup generator and dont isolate the incoming supply.

I don't know the exact mechanism. The VCB would be open if no OLE supply, but the instruction is to lower the pan if no supply for the reason mentioned above.

 

[mike57]

I don't know the exact mechanism. The VCB would be open if no OLE supply, but the instruction is to lower the pan if no supply for the reason mentioned above.

Maybe its 'belt and braces' which when you are dealing with 25kV is a good idea

 

[Elecman]

Pendo's auxiliaries will run for ~ 30 mins - 2 hours depending on whether pantograph is up or down (if left up, will discharge back to the OLE and run down quicker), condition of batteries, outside temperature etc.

I’m pretty sure it won’t be energising the OLE as that would be a very serious safety issue. But the compressors may be having to run to keep the panto up

 

[modernrail]

The OLE trips, somewhere on the network, several times a day. Three things are the main causes:

1) problem with the train
2) wind blowing something into contact with the OLE
3) nobody knows.

It’s not an ‘unabated surge’ but the monitoring systems detecting a short circuit somewhere.

Interesting, thanks Bald Rick!

 

[Archvile]

I’m pretty sure it won’t be energising the OLE as that would be a very serious safety issue. But the compressors may be having to run to keep the panto up

That rings a bell, most likely the reason. Compressors running = dead battery.

 

[Tilting007]

Same section tripped twice again last night, so some sort of underlying cause to be found….

 

[Horizon22]

How often does that sort of thing happen? Is the cause usually some sort of unabated surge that sneaks though whatever the safeguards are?

Could it also trip things on the train?We noticed the power sockets went and the guard reset them.

Regularly. Maybe it happens on each ECRO (Electrical Control Room Operator) desk once a day at least. Often it is (presumed to be) an unfortunate pigeon smashing into the OLE.

Normally it’s a “trip and close” which means if nothing is noted within a couple of minutes, it’s reenergised. If it trips again there’s a wider issue.

== Doublepost prevention - post automatically merged: 24 Dec 2024 ==

What kind of battery backup for auxiliaries do electric trains have? And how long will things like toilets, lights, and heating work for without overhead power?

Almost all electric trains ‘load shed’ by which critical components are kept on the longest; note “critical” does not include passenger comfort.

HVAC fails within minutes and then systems switch to emergency lighting. Toilets tend to last a little longer but not much. Then eventually the PA/CIS fails and normally the last thing to go is the cab GSMR. The whole process ranges from 60-120 minutes depending on the overriding conditions.

If it’s prolonged, pantographs should be lowered.

 

[Nym]

That rings a bell, most likely the reason. Compressors running = dead battery.

The compressors (Air Supply Units) run off of the Auxiliary Supply that isn’t battery backed.

I’m not sure where this “pan up, more battery discharge” thing is coming from, other than a significant simplification for the train operators.

If (all) lighting was lost on a 390, that would have been an AUX Trip not just OLE.
An OLE drop out sets off (consequentially as a loss of the Auxiliary Converter Modules, thence Battery Charger Proven) several timers and voltage relays that routinely disconnect loads as they’re not needed.

Loss of most lighting on the other hand, that could have been from a loss of OLE, with some really, really unhealthy batteries. But given the requirements for service I’d doubt that would be the case

 

[renegademaster]

Auxiliary Supply that isn’t battery backed.

It must come from somewhere to be able to put them up when they aren't already connected to power?

 

[800301]

It must come from somewhere to be able to put them up when they aren't already connected to power?

The pantograph uses the same Main Air Res supply as the rest of the train, a compressor doesn’t have to be running to have the pan up as the main air res will still have pressure, until that drops which depends how how well sealed the system is and any leaks, it can hold pressure for quite a while.

While I don’t know the inns and outs of a 390, a 387 has a separate auxiliary compressor that does run on battery supply to just put the pan up if the train does not have sufficient air supply, I’ve not yet been in a situation where the train has had to use that system

 

[Nym]

It must come from somewhere to be able to put them up when they aren't already connected to power?

There’s an aux compressor that is battery and/or hand operated that has a check valve and only feeds the Pantograph

 

[Archvile]

The compressors (Air Supply Units) run off of the Auxiliary Supply that isn’t battery backed.

I’m not sure where this “pan up, more battery discharge” thing is coming from, other than a significant simplification for the train operators.

If (all) lighting was lost on a 390, that would have been an AUX Trip not just OLE.
An OLE drop out sets off (consequentially as a loss of the Auxiliary Converter Modules, thence Battery Charger Proven) several timers and voltage relays that routinely disconnect loads as they’re not needed.

Loss of most lighting on the other hand, that could have been from a loss of OLE, with some really, really unhealthy batteries. But given the requirements for service I’d doubt that would be the case

Can you explain the mechanism behind the raised/lowered pan generating such a large difference in the time auxiliaries will be available for?

Is it as simple as pan up = compressor(s) running then?

The discharge theory was what we were originally told in the classroom, but I'm aware that the propagation of myths is rife on the railway, like neutral sections being there to prevent outages in one area affecting another area (apparently untrue/not the primary reason).

 

[Nym]

Can you explain the mechanism behind the raised/lowered pan generating such a large difference in the time auxiliaries will be available for?

Is it as simple as pan up = compressor(s) running then?

The discharge theory was what we were originally told in the classroom, but I'm aware that the propagation of myths is rife on the railway, like neutral sections being there to prevent outages in one area affecting another area (apparently untrue/not the primary reason).

No, because as I alluded to, the pantograph being up makes little difference. Unless there are other systems that also shut down that draw on the battery.
(And I’m not digging my schematics out on Xmas eve)

 

[cool110]

like neutral sections being there to prevent outages in one area affecting another area (apparently untrue/not the primary reason).

They do do that, but only as a side effect of separating areas on different phases or feeder stations. The primary reason for them is that those gaps can't be bridged together. To get 25kV between phase and earth you need 43kV between phases, which would be very bad to short out. Going between the same phase from different feeders isn't as bad at the site, but causes problems for the ECOs and NESO as their switching gets bypassed by energy flowing in the wrong direction.