How long till fibre goes down in power cut?

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#1931021 5-Jan-2018 20:00

It depends on the exchange in regards to the power that is being supplied. Larger ones have generators, smaller ones only have battery backup.

The generators are tested monthly and from memory have 7-21 days of Diesel to keep them going depending on their business importance and size of the tanks so that's plenty of time before they will need to be refilled.

The battery only exchanges I think were good for 4 days. They also can take a generator being cabled in if power is going to be off for any longer so if needs be one will be dropped outside.

All DSL cabinets have battery backup to keep them that I think is good for 24-36 hours.

All of the above could be completely wrong as I am going from very vague memory on this.

The comms I have seen today include: 31 PSTN cabinets and exchanges with mains fail alarms running on backup power with varying capacity.

I'm sure the impacts will be minor as this isn't Spark and/or Chorus's first rodeo and Christchurch Earthquake has proven out the BCP plans.

The main impact will be downed overhead cables and how quickly they will be repaired on a per customer / smaller area basis.

and

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#1931034 5-Jan-2018 20:30

The standby power alternators will basically run indefinitely. They usually have a main tank outside the building, the contents of which are pumped into a header tank inside. The header tank has a float switch that controls the header tank pump.

Going back a few years now. The alternators used to be tested monthly by swtiching off the mains and be run for about an hour. The output would be checked for correct voltage and frequency.

The header tank pump auto fill function would also be tested regularly by draining the header tank back into the main tank. There was also an hand pump in case the header pump failed.

All in all the system was very robust both in design and in the testing/checking processes. The chances of there ever being an exhange failure due to a power failure at a main exchange was pretty well zero.

Even the chance of a smaller battery only exchange failing due to a power supply was virtually nil. If necessary a portable alternator was brought in.

All exchange batteries were discharge tested at regular intervals to test their capacity and were replaced when they fell below acceptable limits.

It really was a gold plated belts and braces system

I don't know what standards apply today but I never recall any exchange falling due a power outage during my time in the game.

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MadEngineer

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#1931047 5-Jan-2018 20:54

chevrolux:

Yea no idea what the official expected time is. But at Palmy exchange there is an enormous amount of battery power, and then there is also a huge genny. I would of thought it could essentially run on genny power indefinitely provided a supply of fuel was there. Stand to be corrected, but from memory pretty much anywhere there was a NEAX there is a genny (off the top of my head in the Manawatu area anyway). The smaller RLU's (dotted in suburbs and out in rural areas) just have batteries but can all have a genny hooked up to them.

I'll never forget that room/floor full of batteries.

My response upon first seeing it was; wait, those are not structural I-beams - that's power distribution!

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#1931052 5-Jan-2018 21:16

MadEngineer:

I'll never forget that room/floor full of batteries.

My response upon first seeing it was; wait, those are not structural I-beams - that's power distribution!

I recall being on a course and visiting the battery room at the Caro Street CAX and see the boardwalk part way up the sides of the cells so that it was possible to service the batteries. I don't recall the size now but the cells were higher than the average person, hence the need fo the boardwalk. I'm guess each 2.2v cell would have been about 750 mm square or possibly larger.

Even much smaller exchange batteries had an awesome capacity to deliver a prodigious amount of current as was demostrated on occasion. I remember new batteries being installed, the electrician slipped with the spanner touching the live side to the frame carrying the cables from the battery room to the switchroom. The frame was earthed. Outside in the power room where I was standiing the nuts on the bolts holding the frame together turned red hot and dropped off onto the floor. These were only 500 A/H batteries.

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chevrolux

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#1931150 6-Jan-2018 09:14

MadEngineer:
chevrolux:

Yea no idea what the official expected time is. But at Palmy exchange there is an enormous amount of battery power, and then there is also a huge genny. I would of thought it could essentially run on genny power indefinitely provided a supply of fuel was there. Stand to be corrected, but from memory pretty much anywhere there was a NEAX there is a genny (off the top of my head in the Manawatu area anyway). The smaller RLU's (dotted in suburbs and out in rural areas) just have batteries but can all have a genny hooked up to them.

I'll never forget that room/floor full of batteries.

My response upon first seeing it was; wait, those are not structural I-beams - that's power distribution!

I would love to see what happens if say a screw driver was dropped between some live plates. Would be such a site!

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#1931176 6-Jan-2018 11:31

Or a sight, too.

Aredwood

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#1931179 6-Jan-2018 11:38

chevrolux:I would love to see what happens if say a screw driver was dropped between some live plates. Would be such a site!

That would be both fun and scary to see. As arc welders typically only output around 50V no load, and often a lot less under load. As they are basically just a large constant current power supply.

I'm just picturing the amount of short circuit current available at 48V, and the damage that that much current could do. Presumably the bus bars have been designed with enough separation, so that If a short occurs. The gap will be too large for an arc to be sustained after the thing that caused the short has melted away or exploded.

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#1931214 6-Jan-2018 12:22

chevrolux:
MadEngineer:

chevrolux:

Yea no idea what the official expected time is. But at Palmy exchange there is an enormous amount of battery power, and then there is also a huge genny. I would of thought it could essentially run on genny power indefinitely provided a supply of fuel was there. Stand to be corrected, but from memory pretty much anywhere there was a NEAX there is a genny (off the top of my head in the Manawatu area anyway). The smaller RLU's (dotted in suburbs and out in rural areas) just have batteries but can all have a genny hooked up to them.

I'll never forget that room/floor full of batteries.

My response upon first seeing it was; wait, those are not structural I-beams - that's power distribution!

I would love to see what happens if say a screw driver was dropped between some live plates. Would be such a site!

Are you talking about the plates in the battery cell? As you possibly know many exchanges batteries used to be open top cells with the plates and electrolyte open the the atmosphere. There were glass plates arranged to cover most of the exposed area, but the cells were still open. When a boost charge was being applied there was a lot more hydrogen gas released from the cells, the glass plates would help contain the splashes from the bubbles of hydrogen, and also help stop debris from dropping into the cell.

We used to read the S.G.s by placing a hydrometer float into the electrolyte. There was alway a smell of hydrogen gas when you went into the battery room particularly during a booster charge. Hence the sign on the door "NO NAKED FLAMES".

So in reply to your statement about the effects of dropping screw driver it would depend.

If it were between to adjacent plates possibly not much would happen. As the potential difference between two adjacent plates is quite small. Over time the plates shed bits from their surface and this stuff drops to the bottom. Gradually it builds up till it bridges the gap between the plates. This is what causes most batteries to gradually fail. You don't see anything spectacular.

It it were across several plates then there may be a bit more to see, perhaps some red hot metal and an increased hydrogen output. It there was a spark and the corrrect concentrations of hydrogen were present then I wouldn't want to be anywhere close by. I seem to remember several years ago an AVO meter being placed on a cell with spectaular results when the metal name/information/plate on the base of the meter made contact with the plate connectors.

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#1931218 6-Jan-2018 12:44

Aredwood:
chevrolux:I would love to see what happens if say a screw driver was dropped between some live plates. Would be such a site!

That would be both fun and scary to see. As arc welders typically only output around 50V no load, and often a lot less under load. As they are basically just a large constant current power supply.

I'm just picturing the amount of short circuit current available at 48V, and the damage that that much current could do. Presumably the bus bars have been designed with enough separation, so that If a short occurs. The gap will be too large for an arc to be sustained after the thing that caused the short has melted away or exploded.

The arc distance for a 50 volt supply is pretty small. The bus bar gaps were way way more than that. If there was ever a short, generally the material causing the short would turn red hot and melt breaking the short circuit. There wasn't a great amount of sparking going on.

Wearing metal band wrist watches was not a smart idea while doing any work around bus bars.

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k1w1k1d

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#1931231 6-Jan-2018 13:15

That's the reason I never wear any jewellery at work. I have seen the scars from an expanding watch scrap across a car battery. Not pretty, and bloody painful.

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#1931316 6-Jan-2018 14:52

Looking through the UFB documentation https://www.crowninfrastructure.govt.nz/wp-content/uploads/2011/12/Network-Infrastructure-Project-Agreement-NIPA-26-January-2017-redacte....pdf (PDF page 115) it specifies 8 hours back up power supply is required as a minimum and if a generator is not on site, then there needs to be a facility to plug one in.

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#1931435 6-Jan-2018 19:26

chevrolux: I would love to see what happens if say a screw driver was dropped between some live plates. Would be such a ~~site~~ - sight !

I've seen photos, when I am back at work I will see if I can dig any out to share.

Many of the bus bars are rated up to 3000+ AMPs at 48V DC, they get pretty warm when under full load. So whenever screwdrivers / spanners have been dropped across the positive and negative terminals it tends to leave a dent in the bus bar and the tool completely disintegrates. It's covered in the Chorus Protecting The Network (PTN) videos that everyone needs to take annually if you are going to go onsite into a Chorus / Spark exchange. A quick google will find the first video.

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#1931551 7-Jan-2018 07:07

richms:

Starscream122:

show us a pic of a passive splitter in a street?

They are in the pits that you see them working on occasionally, not much to see there, when I snooped over the sholder of a guy working it just looked like coils of the thin fiber that they were joining onto the ones going to houses.

I'm on Auckland's North Shore and several times I've seen open Chorus pits that have what looks like a stack of white dinner plates extending out of the pit. I assumed that the fibre cables were somehow connected to whatever this stack thing is. Is that a passive splitter?

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#1931554 7-Jan-2018 07:32

https://www.pcworld.co.nz/article/481730/pictures_ufb_-_chorus_fibre_home_installation_part_2_/

this might be one in a cabinet

i imagine they are much the same in the pits

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#1931555 7-Jan-2018 07:32

Hi, "white dinner plates", this sounds more like a splicing cassette, ie where the splice joints are housed, but the splitter can be attached to that assembly depending on exact setup.

Cyril

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