epox; A surge or voltage rise easily provided by a faulty neutral could puncture insulation that then 'leaks current'. Typically very little current but often enough to trip GFI (Ground Fault Interrupter protection). The leakage can, over time, further damage the insulation system leading to either a short that typically gets detected by the circuit protection, but, can also be less than that needed to trip the protection but more than enough to reach ignition temperatures.
A 'sag' or 'brown-out' doesn't bother conventional incandescent lighting one bit but modern CFL (Compact Fluorescent Lighting) or LED lighting controllers can be damaged by low voltage. Modern lighting uses 'switching power supplies' (an efficient type of power controller). Switching supplies dutifully try to supply constant power to their loads and these supplies supply all computers, lighting, wall-warts, cord-warts, expensive refrigerators, speed controlled blowers, etc., etc.
Remembering: Power = Voltage x Current
When a switching supply's supply voltage drops it tries to make this up by drawing more current. However, the cost of all these electronics is a function of the current. More current requires larger silicon, larger silicon costs more, so designers optimize their product designs to use the smallest (cheapest) semiconductors which makes the devices considerably more susceptible to out-of-spec supply voltage damage.
If a brown-out lasts very long or a device is running hot at 'this moment' the low voltage will overheat the controller semiconductors and they'll fail.
Motors are also this same type of constant power device that will draw more current if the voltage drops resulting in rapid overheating. Overheating a motor results in reduced efficiency, future hotter running, and a shortened life.
Most devices have been 'listed' and demonstrably are supposed to be burn-out-able without causing fires. However, the testing regimes often don't take into account a product being run or subjected to unusual voltages so the actual failures caused in those cases are probably less understood and can lead to product fires.
Thanks for the reminder itsmoked. I know some of this has been discussed earlier in this thread and shamefully I am the one asking but I am not knowledgeable about electricity and some of what has been covered earlier has faded from my memory. I was, in fact just rereading the entire thread.
One really does have to read up on the bidding process in the UK & Europe. The Grenfell Tower Refurbishment contract was a Pre-qualified, Two Stage tender process, where the Design/Builder first provides a bid and their thinking & approach to carrying forth the Architects design at the price they bid. If the purchaser accepts the bid, there is an agreement in place but not yet a contract and the contractor then sets about assembling a group of subcontractors to carry out various aspects of the work, who themselves make suggestions regarding the execution of the work. There is then a final agreed upon price and the Contractor will be paid this sum regardless of whether it costs more of less. Don't hold me to accuracy on this but the two-stage process is not favored by the industry but by the purchasers.
It all seems quite fuzzy, which is great for wheeling & dealing but maybe not so good if you are a purchaser like KCTMO with virtually no in-house experience on a extensive refurbishments, Ultimately, in the first go, they would have benefited from a more constrained & formal contract. Most refurbishment projects to social housing had previously been done by the Council itself, through Construction Management companies. The Council's constitution regarding the Tenant Management Organization had been rewritten and KCTMO's management agreement with the Council called for their having greater responsibility regarding large projects on properties under their control.
A couple of questions which I can't answer but which are relevant to your points above:
[ul]
[li]Was the building supplied from the utility's high voltage system, or was it supplied directly at low voltage?[/li]
[li]In whose ownership is the HV/LV transformer and substation feeding the building?[/li]
[/ul]
If the utility intake is at high voltage then the problem rests squarely with the building owner because a neutral fault is exclusively confined to the LV side of the distribution transformer (the high voltage side is 3-wire delta; there's no neutral).
Without some idea of the cabling design it is conjecture, but given the number of anecdotal reports of problems throughout the building my guess is that the neutral failed somewhere close to the transformer or main LV switchboard. The distribution system probably looks a little like the roots of a tree, gradually thinning out and becoming more numerous the further from the transformer and main switchboard they get.
The 'buzzing meter' may be a coin-operated type, and the buzzing is sometimes caused by the magnetic yokes of the contactor not seating cleanly. Irritating but not harmful - it's a noise which would keep me awake.
Thanks ScottyUK, the only substantive information we have to go on is the building design, it was designed as an open floor plan, so it could be converted to office space if that was a future need, it had a plant in the basement with boilers & water pumping facilities to distribute water to Grenfell Tower & the three housing blocks. Possibly the water pumping facility would be the only thing requiring the higher voltage.
Seems other have given some quality thought to how the 2013 power surges may have played a roll in the Grenfell Tower Fire. Link Link
This post on May 28 2013 from the Grenfell Action Group is interesting because it suggests that Data Logging was already in place BEFORE the May 29 2013 catastrophic power event. The question is if it was scheduled for installation or was actually up and recording. I assume Data Logging provided by UKPN would be strictly supplier side. Another bit of information that may or may not be useful is the statement that "Key Meters" were fused by the power event on May 29. I'm thinking Key Meters are prepayment meters in each flat.
I think we have established the 2013 Power Surge events of May 2013 are worthy of a critical examination leading up to the Grenfell Tower fire. There are 22 "perfectly" unscathed Flats from the Forth Floor & up that could be examined and other that may not have had their major appliance affected by the fire.
December 2 2014 – New Window Detail is submitted to RBKC Planning & Building Control as a Non-Material Change for a smaller window size. January 2 2015 – RBKC Planning & Building Control - Jonathan Bore’s Decision letter of accepting the Non-Material change. March 2015 – Harley Facades is well into installation of the first set of windows on the North Façade. (KCTMO March Newsletter w/ photo)
and then May 3 2015 – Report to RBKC HOUSING AND PROPERTY SCRUTINY COMMITTEE Grenfell Tower Project
"The scheme is 7 weeks delayed, which has been agreed by an Extension of Time being issued, which gives a new completion date of 23 October.
The delay has been caused by planning issues associated with the new windows and late demolition work."
Since there wasn't any delay in accepting the Non-Material change, it seems more likely that at some point a building inspector reported that the new window scheme was wonky and compartmentalization was a problem.
From the BBC
Aluminum composite material (ACM) with mineral wool insulation have now failed the Building Research Establishment (BRE) tests. Link
I thought this would have a chance of passing but NO.
We have discussed a lot of these cladding fires in this forum. The main difference in the Grenfell fire is the loss of life. And it was closer to home for many of the posters. As well, it was a refurbishment, while the others were new construction.
The full terms of reference for the public inquiry, which have been accepted in full by the prime minister, are:
The cause and spread of the fire
The design, construction and refurbishment of Grenfell Tower
The scope and adequacy of the relevant regulations relating to high-rise buildings
Whether the relevant legislation and guidance were complied with in the case of Grenfell Tower
The actions of the local authority and other bodies before the tragedy
The response of the London Fire Brigade to the fire and the response of central and local government in the aftermath
The thing that leaps out at me is the "and other bodies" bit in the fifth bullet. Given a sufficiently inquisitive Counsel for the Inquiry, that ought to give them licence for a pretty thorough exploration. Interesting though that there isn't a similar set of words in the final bullet (considering the experience of Hillsborough, where setting an arbitrary time to mark the start of the aftermath was controversially used to curtail the scope of the 1989 Inquest).
zeus... you'd think so, but, not knowing the 'pecking order' of their establishment, you likely don't know. That they've omitted the social aspects/causes makes you think the inquiry will be somewhat 'crippled'.
Reading a bit more about events at Grenfell Tower in 2013 which may be relevant to the 2017 fire:
It seems to be the case that the building is supplied at low voltage from the public system rather than having its own HV intake and local substation.
A problem appears to have occured on the supply cable to the building which resulted in a high resistance or open neutral condition either in the cable itself or, more likely, at a joint in the cable.
It would be interesting to know a little more about the 2013 fault, and what was done to repair it, because it seems plausible that the 2013 repair has failed or the same problem has occurred again at a new location. Accurate technical reports don't appear to be readily available, but there are several references to a serious problem in 2013 which could well be the precursor to the 2017 fire.
Seems that way - the symptoms described are certainly similar, with brownouts, surges and a handful of appliance fires occurring. In the 2013 event the failed neutral appears to have occured externally to the building on an underground cable. Cable faults are rare in cables which are correctly layed and backfilled, but poor installation techniques can damage the cable which leads to failure many years later.
I also wonder - in a purely speculative way - whether the cable has a reduced cross-section neutral compared to the phase conductors and the basis that a well-balanced load would not result in a large neutral current. If the load became sufficiently imbalanced then it is possible, in theory at least, that the neutral conductor would be under-sized for the current it was carrying. This type of cable was definitely used in the early 1970's.
If indeed the problem was external to Grenfell Tower, then the cause of the electrical problems should have been recorded. Peter Maddison – Director of Assets and Regeneration, the Head Honcho for KCTMO on the Grenfell Refurbishment project, told the RBKC Council that subsequent to the power failure, monitoring equipment (Data Logger) had been set up. If the data-logger was set up externally, wouldn't this have been done by UKPN, the power distributor or does/can one hire a contractor to perform supply side monitoring? What good would private data logging serve if the issue was caused by UKPN? If the Neutral Fault was external, how did KCTMO's contractor find it, via an in ground vault outside the tower, excavation? Supposedly the root of the problem was finally discovered over a 12 hour period, when all the residents had their power shut off by the contractor.
Leadbitter working on the KALC project adjacent to Grenfell Tower, denied that their work had anything to do with the power problems at Grenfell Tower. Here is a pre-construction site plan that, as near as I can tell, shows the power supply to Grenfell at the South side of the tower, running East, then Northeast across the park, up to Verity Close & on to Silchester Road; bisecting the KALC Project. Link
Surely at some point in the work done on the KALC project the power to Grenfell had to have been a complication. Maybe the original site work was fine and the temporary work around was not. That is, if the site plan & my interpretation is accurate.
When Peter Maddison – KCTMO Director of Assets and Regeneration told the RBKC Council's Housing & Property Scrutiny Committee that some of the residents had confused smoke with steam & the bulk of the Committee bought into this nonsense, it becomes hard to believe the Council was concerned with anything more than being able to distance themselves from the problem and thus the entire exchange between the Council Committee & KCTMO becomes suspect. It seems only the Council Woman representing the Estate took offense with the explanation. Anytime I've been offered mealy-mouthed explanations that stoop to implying utter stupidity by some other party, my confidence in the person voicing the the explanation takes a nose-dive. How does one confuse the acrid smell of an electrical fault with steam?
So the setting is as follows:
A contractor is working adjacent to Grenfell Tower, whose work may or may not have been the cause of power problems at Grenfell Tower.
A power problem that by resident accounts went on for 3 weeks leading to a catastrophic power event.
45 Flats, all on the upper floors of Grenfell Tower experiencing some loss of property because of the catastrophic power event.
Full renewal of Grenfell's rising electricity main.
And subsequent Data Logging.
No suggestions by the Council or KCTMO that Max Fordham, the Mechanical & Electrical Consultant for both the KALC & Grenfell Projects, make any kind of a Survey of the Grenfell Tower electrical services in advance of the refurbishment project.
I am ignorant on electrical but how does an external fault, fry appliances on just the upper floors, over 30% of the flats. Presumably, fry the main electrical riser yet the lower & intermediate floors are unaffected, even though they all experienced power issues? Separate mains?
It is too bad that none of the resident groups never thought to make a freedom of information request for the Data Logging. Most information regarding Council property operations are run through the Tenant Management Organization and KCTMO is a private enterprise, so it is a freedom of information black-hole but KCTMO doesn't own the property, the Council does so, a freedom of information request on the UKPN data-logging to Grenfell Tower may have been a Power Distributor/Owner record beyond the power of KCTMO to keep private.
If the neutral fault occured in the main feeder cable then everything downstream of it would experience the symptoms of the fault - i.e. variable, load-dependent line-neutral voltages. I'm not at all clear on how the building power is distributed but it is vaguely possible that the top third of the building is on one phase, the middle third on a second phase, and the bottom third of the building on the third. Not how I would do it, but not impossible.
A single-line diagram of the building power distribution would be invalauble in ending the speculation, although I doubt one is likely to surface.
