[AusNOG] DC undervoltage issues

[James Braunegg]

Dear Joshua

Very good questions you ask... and a step away from the normal networking posts, that being said I love datacentre infrastructure just as much as I love networks ;)

For me I did the exact math's you talked about, cost of power over a year paying a fixed price, versus the cost of power over a year at a reduced cost knowing you might need to turn off mains power in periods of high demand or pay the penalty of additional costs.

Bevan makes a great point however knowing when the network is "stressed out" gives you time to act and respond and swap power in a controlled manner.

Whilst datacentres are designed to react to the sudden loss of power and not be service affecting a smooth transition is always preferred.

This is no different to say looking at the weather outside knowing there will be lots of wind and it "might" make sense to predict mains failure and run on diesel generated power, giving you control of the situation... The day and life of running a datacentre !

Because our power requirements are only 1MVA compared to Bevan's huge 22MVA our electrical supply is considerably smaller, thus the difference (saving) between a fixed cost vs the reduced cost to shutdown mains supply at periods of high demand is also minimized. Obviously the greater your requirements the greater the saving so the larger you are the more it makes sense.

Like anything one could say there is a risk in swapping from mains to internal generator power, but like everything there is always a risk associated with change either in a controlled or none controlled environment.

As for cost, 1MVA requires around 180 L of fuel per hour (Give or take different engine efficiencies)

So based on today's fuel cost which is 161.84 cents per L you're looking at about $290.00 per hour per 1MVA

Hope this answers your questions

Kindest Regards


James Braunegg
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From: Joshua D'Alton [mailto:joshua at railgun.com.au]
Sent: Wednesday, January 15, 2014 11:40 PM
To: Bevan Slattery
Cc: James Braunegg; AusNOG at lists.ausnog.net
Subject: Re: [AusNOG] DC undervoltage issues

Cheers James and Bevan.

And I assume the "super high price" for electricity is substantially higher than the cost of running the generators in that period (ie capex/depreciation + cost of diesel < cost of power)? Can you comment Bevan on if its close, or far away from utility power costs in general? as in its obviously more expensive to power the DC via diesel long term (either due to raw fuel cost or with generator costs included), but how close is it? and further, how much of a bet/risk is it to purchase the cheaper power with these restrictions (having to go off-grid or else pay a premium)?

I'm guessing its probably a case of using historical data and just match things up to work out how many days per year on average, the cost of diesel and generators during that period, and making sure its less than the X% more per year paid for utility power with no usage restrictions, ?

Might be another thread for this, or even off-list, but I'd imagine listers would find this interesting or useful.

On Wed, Jan 15, 2014 at 11:30 PM, Bevan Slattery <bevan at slattery.net.au<mailto:bevan at slattery.net.au>> wrote:


From: Joshua D'Alton <joshua at railgun.com.au<mailto:joshua at railgun.com.au>>
Date: Wednesday, 15 January 2014 10:17 pm
To: James Braunegg <james.braunegg at micron21.com<mailto:james.braunegg at micron21.com>>
Cc: "ausnog at lists.ausnog.net<mailto:ausnog at lists.ausnog.net>" <ausnog at lists.ausnog.net<mailto:ausnog at lists.ausnog.net>>

Subject: Re: [AusNOG] DC undervoltage issues

> Does the energy provider call up the DC and say oh hey, as per agreement go onto generators for X hours thanks, your next bill will be credited ABC ?).

Goes like this:

Option 1: Energy Provider rings and says due to network instability can we ask you to shed xx% of load over this period of time
Option 2: Major DC rings energy provider and says we are seeing network instability - we are considering moving over to internal power.  What is your advice/recommendation (graceful exit from grid)
Option 3: Power is outside of tolerance on one or more feeds and the DRUPS engines kicks in - no phone call required, but courtesy call is usually given post fact (all in LV side and the DC's control)
Option 4: Loss of HV power to site will require call to provider for approval before bringing back on grid (safety and capacity confirmation)

The rest of the "commerciality" is confidential.

[b]

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