[AusNOG] DC undervoltage issues

[John Lindsay]

Quite a lot of DCs would have switched to generator power over the last couple of days under commercial agreements that pay them to go off grid when the wholesale price spikes. 

A site with non ups B feed might be showing low voltage in such a mode. 

jsl

> On 15 Jan 2014, at 10:22 pm, Joshua D'Alton <joshua at railgun.com.au> wrote:
> 
> Ah yes of course, it'd be the AC. Though I'd have thought the AC wouldn't be in the circuit after the UPS, but I suppose in the event of power failure they still need to cool the DC. Still, sounds like they didn't spec the system for the peak load, or maybe they did but as a result of all the extra equipment vs when the DC opened. Anyway, questions I'll be asking and following up on SLAs.
> 
> 
>> On Wed, Jan 15, 2014 at 10:46 PM, Tony de Francesco <tonyd at pue.com.au> wrote:
>> Another thing to consider: if the DC cooling system is served by air-cooled DX CRAC units or air-cooled chillers, the power draw of the cooling system on a day like today would be at its absolute peak. Such an event will place additional current draw on the main power feed to the site and potentially drop site voltage.
>> 
>> However, if a double conversion static UPS system is in place and operating without fault then you should not be seeing a voltage drop.
>> 
>> Regards
>> 
>> Tony de Francesco
>> Technical Director
>> P.U.E. Pty Ltd
>> Mob: +61 (0) 457 701 179
>> Email: tonyd at pue.com.au
>> 
>>> On 15/01/2014 10:35 PM, "Tony de Francesco" <tonyd at pue.com.au> wrote:
>>> joshua,
>>> 
>>> Undervoltage at the street mains supply to the DC would probably be the result of excessive power draw on the main electrical grid.
>>> 
>>> However, if a double conversion static UPS system is used as the main DC UPS, the A+B supply voltage should remain at a very stable 240V AC.
>>> 
>>> Many new UPS systems are designed for lower losses and deliver power straight through with some minor voltage regulation  (known as line intetactive UPS).
>>> 
>>> It could bd possible that the DCs main UPS is in bypass mode (due to a fault or maintenance) in which case you would bd seeing the street voltage.
>>> 
>>> Another less likely possibility is that current draw within the DC is at a peak and cresting excessive voltage drops.  
>>> 
>>> Regards
>>> 
>>> Tony de Francesco
>>> Technical Director
>>> P.U.E. Pty Ltd
>>> Mob: +61 (0) 457 701 179
>>> Email: tonyd at pue.com.au
>>> 
>>>> On 15/01/2014 10:15 PM, "Joshua D'Alton" <joshua at railgun.com.au> wrote:
>>>> Evening noggers, hope you're all surviving the heat, especially in VIC!
>>>> 
>>>> Speaking of, in 2 DCs were seeing borderline undervoltage on our UPSs (yes we run them even with A+B power because sensitive equipment), I've read that there are power issues in VIC at the moment, but I thought they were limited to residential zones (with rolling black/brownouts)?
>>>> 
>>>> Anyone else seeing this, or have comments?
>>>> 
>>>> As a side question, does anyone (perhaps Bevan?) know if DCs will manually switch to genny/backup power in this sort of scenario, if so details would be nice.
>>>> 
>>>> (with regards to that, I looked at one DC contract and it doesn't mention anything about the specifics of power delivered, just that it is A+B with X battery backup and Y generator capacity, and Z SLA, doesn't mention what sorts of voltages would break said SLA...)
>>>> 
>>>> Anyhoo, cheers!
>>>> 
>>>> PS, also seeing strange intermittent issues with Telstra and Pacnet connecting to local google and others, not sure why the power quality would affect that, but..
>>>> 
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> 
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