Sydney T2 Blackout

[Greg Hyde]

Sydney T2 was affected by a power outage for most of the day.

http://www.abc.net.au/news/2014-06-27/sydney-airport-power-cut-qantas-virgin-rex-jetstar-holidays/5554764

You would think that airports are critical pieces of infrastructure that need emergency generators to keep them running during blackouts.

With a couple of diesel backup generators could Sydney airport operate ?

[Michael Cleary]

From the Sydney Airport Web Site:

"Sydney Airport has identified an issue with a substation, which caused the power interruption and affected back-up power sources."

Hardly a back-up if it passes through the same place.


Not the first time that a power issue in a terminal has caused chaos either.

[Greg Hyde]

It's known in the bus as "a single point of failure".

[Michael Cleary]

That's like me having a backup power supply to my house - two separate cables coming from the same pole in the street, one to the normal switchboard, the other to the backup.

Then a truck his a pole further down the street - and takes out both supplies.


Sounds like their backup supply has been done on the cheap.

[Hugh Jarse]

You can't expect much from SACL. That would require investment in infrastructure. And they won't invest in anything they can't directly make a quid from......

[Sarah C]

Bring on the second airport now............

[Ash W]

That's like me having a backup power supply to my house - two separate cables coming from the same pole in the street, one to the normal switchboard, the other to the backup.

Then a truck his a pole further down the street - and takes out both supplies.


Sounds like their backup supply has been done on the cheap.

Good in theory, except of course your main and back-up MUST meet somewhere, normally in a change-over switch which will switch from mains to back-up if mains fails. If the fault is with that switch you loose power.

So simple answer no power system is 100% redundant. I tell of lie of course you could have two totally separate power systems, but that would require everything plugged into it to have dual power supplies. Services and network equipment in data centres do this, but not practical when the devices being connected are terminals and PC, most of which do not have, nor support dual power supplies.

[Greg Hyde]

Ash, I have to disagree, dual power systems exist.

By the use of a Uninterruptible power supply (UPS), the power can be held up until the generator(s) takeover.

A UPS can't run everything but it can run your critical systems (ie: Computer servers) until the generator power stabilizes.

Most mission critical infrastructure have UPS and gen sets. Structures like hospitals, telephone exchanges, computer centres, etc.

I could write more on redundant power & comms systems but I won't bore you. PS. I was in the bizz..

[Ash W]

Greg, I have to disagree, your example is not a dual power system.

All a UPS does, as you quite correctly point out is hold the load whilst back-up power kicks in, read the generator fires up and stabalises, that doesn't make it redundant. It still requires, as I mentioned a change over switch to switch the input to the UPS between mains and generator.

Everything from the change over switch onwards is therefore not part of a redundant power circuit, normally it would be called an essential power circuit. Clearly any fault from the changeover switch to outlet will therefore cause a back-out on that circuit. Also a problem with the generator will also cause a blackout once the UPS has run dry.

The only truley redundant systems is where the circuits are completely separate to the outlet and where the equipment has dual power supplies. Data centre servers and network hardware etc generally being where you would see this set-up.

PS I studied electrical engineering at TAFE back in the day and still work in the bizz in the area of data centres, comms and PABX systems.

[Philip Argy]

I suppose you could theoretically have every power point supplied by two independent sources of power, with an automatic switchover in the power point if the 'primary' source fails, but that is hard to retrofit to an existing building, and how far upstream do you take the redundancy - does it extend to sourcing from separate power stations/back up generators?

In practical terms an enhanced ability to identify the source of a problem and fix it quickly might be more useful and affordable than total redundancy.

[Ash W]

Phillip, both points you make are exactly how it works in the real world. In relation to your first point where you take the single point is all based on risk and cost.

Hence high availability data centres you will find equipment with dual power supplies, feed from completely different sources with appropriate UPS and generator systems.

In a building like Sydney airport you will probably find it is more like what Greg was suggesting above where they have some circuits connected to a UPS, which in turn is feed from mains and a back-up generator. With the UPS being there just to hold the equipment whilst the generator fires up, stabilises and switches over. On an auto generator this could take 30 seconds to a minute.

[Greg Hyde]

Only "mission critical" systems need to be supported by UPS/Gen sets. Equipment that takes some time to restart.

On new builds (on request) you can have two main power feeds from two discrete power supplies that never pass through the same sub-stations.

It can be retro-fitted, at a cost.

[Philip Argy]

Not sure in what scenario T2 is not mission critical - ask the passengers and staff who were there last Friday ... :confused:

[Ash W]

Philip sometimes even with a mission critical design the "you know what" can happen.

A good example was Calvary Hospital in Canberra where it suffered a black-out early last year. This was a result of a heavy rain storm that flooded the room where the mains come in, and also flooded the feed from the back-up generator. The hospital also had UPS, but that only lasted so long, think it was about in hour in the case of the hospital.

Without knowing the design of Sydney airports power feeds, nor what the issue was, it is a tad unfair to go around pointing fingers of blame as others in this thread have done.

[Bradley Porter]

I'll bet the car park pay machines worked just fine throughout the whole ordeal !

[Hugh Jarse]

Apart from the shops, practically everything in a terminal is mission critical. From the heavily-relied upon 2-way comms to the power driving aerobridges and NIGS systems. Then there's the computer and network systems upon which the airlines depend for checkin, dispatch etc.