Nym - most of what you just said went way over my head!
But from what you've said it sounds like there is more chance of a train doing a backflip and landing back on the tracks than a bit of misplaced concrete causing a blackout.
i.e. Not technically impossible, but will probably never happen in the entire lifetime of the universe, and them some.
(BTW my comment about my lights - I meant the lights in my living room and everything else with it, not some traffic lights. And I live about 15 miles from Victoria - but that's beside the point)
That's because in a post 16th Ed. fitted house the cascade rule doesn't exactly apply, you'll have a main incomer that is simply a double pole thermal overload circuit breaker, not very fast reacting to overcurrent but still fast enough. It doesn't need to be fast as it doesn't protect any external circuits.
In order to simplify domestic installations the class of circuit breaker to be used is specified in BS7671. But the basic rule of thumb is that...
An RCD is provided for anything that goes near water, is pluggable or nowerdays, "The failure of which would not result in increased danger.".
RCDs are Residual Current Devices, these detect any leakage of current in addition to overcurrent, such as a small amount of current leaking to earth, or a highly capacitive load (fingers for example) and as such will react significantly quicker than a termal overload circuit breaker, usually a Minature Circuit Breaker (MCB).
Installs today and for approximately the last 15 years the main incomer is a double pole "MCB" rated at around 100A, 80A or 63A, this usually matches the DNO fuse (Usually BS88) but is timed to react faster so that the operators fuse should never blow.
This will then feed the non pluggable circuits and a residual current circuit breaker / residual current device.
Non pluggable circuits running at low current, for example, lighting circuits can be (and are recomended to be) connected upstream of the RCD.
Downstream of this RCD is every other circuit, sockets, shower, cooker, boiler etc. This RCD will likely be rated at 63A or 80A for thermal overload and either 100mA (Pre 17th Ed.) or 30mA residual with an appropriate delay in the order of miliseconds. This delay allows additional or more sensitive RCDs or RCBOs to be installed to individually protect other circuits from earth leakage without triggering the main RCD, for example on shower circuits, or external circuits.
Other pluggable circuits are then fed by MCBs at appropriate thermal overload ratings, or through an RCBO as discribed above.
It is possble and likely in larger installations that two primary RCDs will be used in order that an earth fault will not knock everything out at once.
But this RCD is the one occation where the cascade effect rates things backwards, in this case for cost reduction as the loss of >1 circuit in a domestic installation isn't the end of the world (hence why lighting is usually not RCD protected, as it is also usually rated at 6A or less, so the thermal overload triggers much more easilly than on a 32A socket main or 45A cooker circuit)
In industrial installations, all circuits are protected as required, this can be thermal overload protection only with a non-diversified RCD protection device as in a domestic install (usually the case for comercial installs). Or can sequence and cascade ratings for different fault conditions in order to avod the cascade effect. However, for these installs a much more detailed analysis of earth fault loop impedence, fault current, fault thermal capacity and several other factors is carried out...
Signalling installations fall into this latter catagory
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I'd have thought it would have been a word which starts in F and ends in K
However TfL are saying that they hope services can resume south of Warren Street tomorrow so either they're being very optimistic or its not as bad as we thought, either way there are some engineers in for a long night!
I think they're being optimistic, but I do hope I'm proven wrong. (At best I think it could be running to Victoria, less track circuits and points to prove for that)
No dowbt I'll find out tomorow what's running down there on me way to work...
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Just typical this would happen at a time when I'm going to be visiting Victoria a couple of times a week.
Someone suggested on another forum that it's a solid state interlocking.
The Victoria Line is Solid State Interlocking from Westinghouse / Avensys Rail systems, similar to Westrace. The relays shown are not used to provide interlocking in the traditional sense. They are not interlocking relays.
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PS to many posts above;
Lighting blowing an incandecant bulb will normally knock off an RCD so it's not protected in this way.
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From what I've heard it's almost all been cleared up now and everything is just being checked over by the electrical engineers.
I'd hope it's Signalling Engineers and Technical Officers...