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Author Topic: Lancaster power outage  (Read 856 times)

waltergmw

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Lancaster power outage
« on: June 21, 2017, 02:48:33 PM »

Gentlefolk,

Lancaster residents might be interested to read this:-

https://b4rn.org.uk/b4rn-service/network-status/

I assume all BT ADSL services remain unaffected but does anybody know if there is a published battery duration for the different types of FTTC ?

Kind regards,
Walter
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j0hn

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Re: Lancaster power outage
« Reply #1 on: June 21, 2017, 04:01:20 PM »

I can't find the relative pdf at the moment but I believe the DSLAM's have a 48v battery intended to last a minimum of 4 hours.
I'm often wrong though :-[
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burakkucat

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Re: Lancaster power outage
« Reply #2 on: June 21, 2017, 05:57:06 PM »

All three types of Openreach cabinet (containing a Huawei SmartAX MA5616, a Huawei SmartAX MA5603T and an ECI Hi-FOCuS Mini-Shelf M41, respectively) contain four 12V SLA batteries, in series.

The last time we discussed the available backup time, before total discharge, I recall that the batteries were expected maintain the service for 8 hours. I believe Black Sheep mentioned that Openreach/Operate technicians were expected to attend after 4 hours of outage to perform a battery set swap. However with a wide area mains power outage, I don't think there would be sufficient technicians -- nor charged battery sets -- available to achieve that target.
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WWWombat

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Re: Lancaster power outage
« Reply #3 on: June 21, 2017, 07:41:20 PM »

BT Business' status page is here: https://btbusiness.custhelp.com/app/service_status/

It shows an Infinity problem in the Lancaster area from 12:20 to 15:07, and one in Morecambe from 12:16 to 13:21.

There's a quote on TBB saying:
fully loaded 3-4 hours is expected
partially loaded stands at 6-12
with no load before fully commissioned they lasted a couple of days

As something of a sanity check, we can see how long a battery is likely to last...

The Kitz page on FTTC cabinets shows an AIO cabinet with room for a 26 amp-hour battery.

Back in 2014, Openreach applied for permission to use DSLAMs without meters. As part of this, they told us the power consumption data...
As an example, an MA5616 (ie 128 variant used in an AIO) uses 70W when empty, 160W when half full (64 ports), and 210W when full (128 ports).

At a supply voltage of 48V, that equates to currents of 1.5A, 3.3A, and 4.4A respectively.

If the diagram indicates a 48V battery of 26AH, or 4x 12V batteries each of 26AH, it would last 17 hours, 8 hours, 6 hours respectively.

The 288-port variant looks to have room for considerably bigger batteries, and the glimpse of batteries seen here are of a size that, by my guess, can handle 60-70 AmpHours each.

The 288-port 5603T starts at 100W and peaks at a 600W usage, or 2.1 Amps and 12.5 Amps respectively. Such batteries would last around 28 hours at best, 5-6 hours at worst.

I'm guessing 5-6 hours is a reasonable bet.
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WWWombat

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Re: Lancaster power outage
« Reply #4 on: June 21, 2017, 08:13:41 PM »

Looking a bit further, I found some more hints about batteries...

This video of an ECI cabinet uses a stack of "Haze" batteries: https://www.youtube.com/watch?v=G1RvCEBoiJ4

Concentrating on the Haze brand, I reckon a set of 4 of their 55Ah "front access telecom" batteries could fit into the box in a 288-port Huawei.
https://www.blueboxbatteries.co.uk/brands/haze/hzb-front-access/hzb12-55fa-battery

At a pinch, using the full depth, you might even get a bank of these Exide 86Ah batteries in there:
https://www.blueboxbatteries.co.uk/brands/exide-gnb/marathon-m-ft/m12v90f-battery

Seeing these, I could believe that a DSLAM is given lower-capacity batteries when it has fewer ports in use, but that they could be swapped out for higher capacity when the number of ports increases.

Also, for future note: A G.Fast pod would place additional demand on the batteries.
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waltergmw

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Re: Lancaster power outage
« Reply #5 on: June 24, 2017, 07:39:34 PM »

1.   From a practical viewpoint swapping live batteries will require careful protection of exposed terminal wires and any spanners etc. used so I expect changing batteries might be discouraged.

2.   Another interesting point is the additional charging load after a large power outage, particularly if it happened during peak winter month loads. However, unless we have a New York style blackout the chances of getting even half of the 70,000 odd FTTC batteries depleted must be quite small. Given the VERY low generating margins we had last winter in cold calm conditions I suppose we must expect disruption at some time.
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Ronski

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Re: Lancaster power outage
« Reply #6 on: June 25, 2017, 08:52:50 AM »

You may find that the batteries come as a pack and simply unplug, no spanners required.
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WWWombat

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Re: Lancaster power outage
« Reply #7 on: June 25, 2017, 01:02:18 PM »

A follow-up...

Backup Time
This video confirmed a 6-hour backup:
https://youtu.be/53NcsctuxV0?t=235

I imagine that, with a widespread outage and many houses also losing power, the DSLAMs will last rather longer than when the power failure is localised to just the DSLAM.

Removal
The style I saw the other day look like they can be fixed together in a 288 ...


But they are 18kg each, so moving a fixed pack is likely to need a little help. An external shelf, to pull them out onto?

Recharge
Would recharging a battery pack need to be high current?  We want the batteries to be available 24x7, but after an outage, is there a huge requirement that they be instantly ready again?

At maximum, a lead-acid battery wouldn't normally want to be charged any higher than a current of (capacity/10), to prevent giving off hydrogen gas - so 55Ah would max around 5A. At 48V, that would equate to roughly 1A on mains voltage, for maybe 12 hours (though it would extend much longer, at lower current, with a decent multi-stage charger). It would actively consume around 250W while charging the bulk, and total about 3kWhr.

As far as I can make out, that's about the same power draw as 2 or 3 street lights. Or a couple of fridges. At maximum. If we're that close to the generating margin, there's probably more to worry about.

Incidentally, the 70,000 cabinets in the street don't really represent a new demand on the nation's power generators. Almost every circuit on an FTTC cabinet will have started out as an ADSL circuit on the exchange. All that has happened is to transfer the load from exchange-based to cabinet-based ... and therefore transferred the battery recharge demand from a central exchange battery (that will now need less recharging) to a distributed set.

Lancaster
Was there any reported outage from cabinets running out of battery?
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