4 ms·

I read your list and see a bunch of 'technical debt.' Trains put into operation without the ability to survive a power transient without intervention. Life cr

I read your list and see a bunch of 'technical debt.' Trains put into operation without the ability to survive a power transient without intervention. Life critical backup power system failures. The set of critical sites is not being maintained properly. In my mind these failures are are not entirely unrelated; reliable power is taken for granted and the testing and maintenance necessary to cope with power outages is neglected.

mytailorisrich 7y ago
This is not technical debt. These are signs of oversights or potential poor management. Indeed that's what neglecting these procedures is. This is why a comprehensive investigation is needed to ensure the details are known and all lessons learned or, unfortunately, re-learned.
- walshemj 7y ago
  Its shockly poor procurement - those new trains are not fit for purpose.
  - growse 7y ago
    Do you mean that they don't meet the requirements of the tender spec ("not fit for purpose") or that the spec in the tender process was deficient ("shockingly poor procurement")?
    - deleted 7y ago
      [deleted]
    - walshemj 7y ago
      Both the older electrostars where far better
growse 7y ago
> Trains put into operation without the ability to survive a power transient without intervention. The trains were built to a environmental tolerance spec, and shutting down when that spec is exceeded seems like a reasonable thing to do. Having an expert test that all the safety systems are still working properly after they've been exposed to conditions they weren't designed for also seems prudent. Do you think people should pay higher ticket prices / more tax to fund trains that can tolerate a wider range of input frequencies, given how rarely these sorts of events happen?
- caf 7y ago
  The GP says that the frequency drop was within-specification, not exceeding spec.
  - growse 7y ago
    Which specification though? At the time they were being designed and procured, I think the specified tolerance for frequency change rate on the grid was 0.125Hz/s, but this was relaxed in 2014 to 1Hz/s (see https://www.nationalgrideso.com/document/10771/download https://www.nationalgrideso.com/document/10771/download). How much the effects of relaxing this on existing equipment was considered, it's not clear. Similarly, the grid's license gives them a ±1% variation around 50Hz (so ±0.5Hz from https://www.nationalgrideso.com/balancing-services/frequency-response-services https://www.nationalgrideso.com/balancing-services/frequency...). So we have a power anomaly where the frequency moved >0.125Hz/s and dropped well below the 49.5Hz license threshold. I don't know what the procurement spec was, but I'd be very surprised if this event was "in-spec" for the trains, so in the absence if this it's probably reasonable to say that GP is incorrect. Transformers get quite unhappily melty if you drop the frequency too much, so if your cooling system isn't designed to cope with this, it's probably better to shut down than have an exciting fire.
    - makomk 7y ago
      The grid's license only requires them to be within ±0.5Hz of the nominal 50Hz for at least 95% of the time. Anyone designing a system which needs to operate reliably ideally ought to design it to operate over the full 47.5-52Hz range, or at least not fail so completely it cannot be restarted. Low frequency demand disconnect only starts at 48.8 Hz, ao any system that can't handle that is effectively setting itself up to be the first thing to fail when there's a power shortfall. This is utterly inexcusable for a train given the amount of disruption caused by multiple lines being clogged by failed trains in multiple places.

mytailorisrich 7y ago

This is not technical debt. These are signs of oversights or potential poor management. Indeed that's what neglecting these procedures is. This is why a comprehensive investigation is needed to ensure the details are known and all lessons learned or, unfortunately, re-learned.

walshemj 7y ago
Its shockly poor procurement - those new trains are not fit for purpose.
- growse 7y ago
  Do you mean that they don't meet the requirements of the tender spec ("not fit for purpose") or that the spec in the tender process was deficient ("shockingly poor procurement")?
  - deleted 7y ago
    [deleted]
  - walshemj 7y ago
    Both the older electrostars where far better

growse 7y ago

> Trains put into operation without the ability to survive a power transient without intervention. The trains were built to a environmental tolerance spec, and shutting down when that spec is exceeded seems like a reasonable thing to do. Having an expert test that all the safety systems are still working properly after they've been exposed to conditions they weren't designed for also seems prudent. Do you think people should pay higher ticket prices / more tax to fund trains that can tolerate a wider range of input frequencies, given how rarely these sorts of events happen?

caf 7y ago
The GP says that the frequency drop was within-specification, not exceeding spec.
- growse 7y ago
  Which specification though? At the time they were being designed and procured, I think the specified tolerance for frequency change rate on the grid was 0.125Hz/s, but this was relaxed in 2014 to 1Hz/s (see https://www.nationalgrideso.com/document/10771/download https://www.nationalgrideso.com/document/10771/download). How much the effects of relaxing this on existing equipment was considered, it's not clear. Similarly, the grid's license gives them a ±1% variation around 50Hz (so ±0.5Hz from https://www.nationalgrideso.com/balancing-services/frequency-response-services https://www.nationalgrideso.com/balancing-services/frequency...). So we have a power anomaly where the frequency moved >0.125Hz/s and dropped well below the 49.5Hz license threshold. I don't know what the procurement spec was, but I'd be very surprised if this event was "in-spec" for the trains, so in the absence if this it's probably reasonable to say that GP is incorrect. Transformers get quite unhappily melty if you drop the frequency too much, so if your cooling system isn't designed to cope with this, it's probably better to shut down than have an exciting fire.
  - makomk 7y ago
    The grid's license only requires them to be within ±0.5Hz of the nominal 50Hz for at least 95% of the time. Anyone designing a system which needs to operate reliably ideally ought to design it to operate over the full 47.5-52Hz range, or at least not fail so completely it cannot be restarted. Low frequency demand disconnect only starts at 48.8 Hz, ao any system that can't handle that is effectively setting itself up to be the first thing to fail when there's a power shortfall. This is utterly inexcusable for a train given the amount of disruption caused by multiple lines being clogged by failed trains in multiple places.