I have heard several reports of actual physical damage consequent to the power outage, last on the R4 "Today" programme this morning. Is this actually correct, and if so, what might it be? It was nice to hear some thanks given to the staff who worked to recover the situation too.
I don't know about this specific case, but where I used to work, power blips could cause fuses to blow, equipment that was already likely suffering from degraded components to fail to work when the power comes back (switch mode power supplies are one example of this) or computer based equipment failing to restart with the correct timing and then shutting down (for safety reasons, critical safety systems have to use a majority voting system, at least two processors have to agree, otherwise the outvoted system gets automatically shut down with a requirement that there must be at least two processors still working, otherwise the entire system shuts down).
Going forward, especially now batteries are cheaper than ever (and only continuing to go down in price), wouldn't a sensible future plan be to install battery storage at key locations that means you don't require a UPS to buy time to power up generators, but the batteries can instantly take over - and also step in at any time if the incoming supply fluctuates even for a short period of time.
You could build storage to allow everything to keep going, or just protect key circuits. If the issue is systems messing up if they go offline even for a short time, batteries can ensure this never happens - and obviously the batteries will charge up once the incoming supply is restored (even partly via solar if you have the room).
We are there already. To use batteries effectively you need the means to charge them and also to invert their DC output to usable AC mains. And provide the controls for detecting grid failure and taking over the load mid-cycle.
The combination of all this is what a UPS is.
But it sounds like they use a pretty limited UPS for a short period of time, to allow the switching of power to another source (generator). What I'm talking about is a large battery that can switch instantly to another power source - the battery. It has the inverter and UPS functionality, but is essentially the generator but instantly available at any moment (so is as good as having a second mains power supplier). It can also monitor the power to switch if the incoming supply has issues.
More and more people are buying these for their homes (Anker, Ecoflow, Bluetti, Jackery etc) and I'd certainly do that today than buy a standalone UPS that might run things for only a matter of minutes. Of course, if you're just wanting to keep a computer online to allow you to save (or it saves) data then that's fine, but these days people may want to keep the fridge freezer going, or perhaps even power their gas boiler so they can keep heating their home during a power outage.
Big proper UPSes generally have the ability to add additional battery capacity. But you're still dealing with a different order of magnitude power requirement for a house compared to a ROC with dedicated power feeds. Your domestic breakers are rated at 10s of amps, switchgear on a 6.6kV supply is 1000s of amps. Batteries will also eventually run out, no matter what size of installation you have. Whereas a generator can have its tanks topped up whilst running if you get an extended outage.
But it's still not clear whether the failure was with the UPS kicking in at all. No amount of battery will save you if the switching electronics fail.
The point of my derogatory comment was that nothing gets ‘built’ overnight and alterations are long-lead work.
At best, (for example) it’s possible to hire in a generator set fairly quickly but anything else overnight is just putting things right.
The railway uses proper industrial specification UPS systems. The AC mains supply feeds the UPS. Internally this is converted to a DC supply. This used to both charge the battery (a very large battery) AND supply the inverter (that converts DC to AC). The AC output is then used to supply the load. When the mains into the UPS fails, there is no break in the AC output. That's the whole point of a UPS.
Some of these UPS are the size of a large shipping container... The smaller ones are the size of two washing machines placed side by side. And then there are some that come in-between.
As a standby generator is a requirement (and has been for PSBs from the 1960s), having a UPS with a battery that can last for hours would be using up money for little benefit. As I have said before, the standby generator should auto-start and take the load. The load being the UPS, which in turn then feeds the signalling systems.
The railway has it's own mobile generator sets for use if the fixed installation standby generator has to be taken out of service (for heavy maintenance or due to a fault/problem).
Agreed that with a traditional signalling centre or PSB, it will also supply the external feeders to the lineside equipment, and the generator will backup those supplies. But I haven't seen any cases where the external feeders have been fed from a UPS. You would need a fairly substantial UPS to be capable of driving several point machines simultaneously. The UPSs are only used to power the computer-based kit inside the control centre.
It very much depends on what the requirements are.
Is the requirement just to keep the computer-based systems in the signalling centre running? Then only that would be protected/fed by a UPS.
Is the requirement to have no lost of signalling between the loss of the mains DNO supplies and the standby generator starting up? If so, all the signalling supplies would have to be protected/fed by UPS, including the "remote" (DNO fed) power networks feeding the signalling many miles from where the ROC/signalling centre/PSB is located.
On the area where I used to work, we had both.
The less important lines only had the computer-based systems (an SSI - Solid State Interlocking and PMUX - Panel Multiplexer - both these were made up of a number of computers) fed via a UPS. Nothing else was fed via the UPS. So when the mains (DNO) supply failed, the SSI lost contact with all the TFM (Trackside Functional Modules) and hence the signaller got a "red out" (all track circuits showing occupied, all signals black).
The older, 1970s RRI interlockings and PSB that controlled the main lines had 650V AC UPS retro fitted to feed all of the signalling equipment. Why? Because just the disruption caused by the changes of signal aspects caused by the less than a minute power loss was considered unacceptable. So the money was found to retro fit 650V AC UPS systems.
There's surely no way that they're powering the lights etc 50 miles away from this facility??? The AC losses involved would be absolutely insane.
You seem to have missed the word "local" in Annett's message. Traditional 650v signalling feeders can stretch considerable distances, and I suspect the latest HV 3 phase feeders even further, but I doubt 50 miles. Remote areas will have their own supply points.
On non-electrified lines the railway has DNO feeds that supply power distribution points (which include their own standby generators) every five to ten miles (often located at junctions). This is for the railways own lineside 650V AC distribution network that feeds the vast majority of the signalling equipment.
Surely not? If you kept interlocking but lost the control system itself then at least you havent lost all the positions of the trains (etc) and it's far easier for the control system to boot up again.
That's not how the signalling system works. The indication and control systems are slaves to the interlocking (to be pedantic, a special module that is directly connected to the interlocking rather than the actual interlocking, but all in the same rack). They only do what they are instructed to do. So what they show is the current state from the interlocking.
The interlocking only keeps it's state of the railway information for a very short amount of time (measured in milliseconds). If it cannot communicate with the equipment that is lineside, it updates it's state of the railway information to a "fail safe" state - track circuits are considered to be occupied, signals are marked as being unlit (black) and points are considered to be not detected.
Tbh I'm more familiar with data centres but it is pretty terrifying if this isn't the case. You need building HVAC on it otherwise stuff starts overheating and you get cascading failures (the most common failure type in datacentres isn't power failing, it's HVAC going down and temps rising steadily and causing outages that way).
The aircon systems can safely be fed from the standby generator supply. No need for them to be fed from a UPS.
If the standby generator doesn’t start, you very quickly won't have any operational signalling anyway.
