So maybe two issues
- Equipment is installed at N+1 with 50% load for N, but now load is 80% N. Pretending to be RAID1 with a hot spare, but which is actually RAID0.5 with a hot spare.
- When you assume you have an option to do a boost on specs - turn 15MW into 30MW - but this is dependent on heat levels. Plan to do work when it is cooler.
Power infrastructure is expensive and these guys try to get them moneys worth. The transformer in my street was giving me constant low voltage, Vector's answer was to switch me to a new phase. Now I only seem to get low voltage at 6pm in winter when people get home. It might be ok to do this stuff for one street - but if they doing this for core infrastructure this issue is going to keep happening.
On Wed, Feb 4, 2009 at 11:32 AM, Richard Naylor
<richard.naylor@r2.co.nz> wrote:
At 11:13 a.m. 4/02/2009, Dean Pemberton wrote:
>They had n+1
>They took down the +1 for regular maintenance leaving them n.
>Then one failed leaving them n-1.
>Then the remaining unit could not carry the load and shutdown to protect
>itself.
Actually they may have had (n+1)x2 or some factor like 2.
On big transformers is common to have oil pumps and fans on the
radiators. So you can turn a 15MW tranny into a 30MW tranny (or
whatever the manufacturer has calculated). Of course if you were
already running the pumps and fans, then it doesn't help.....and you
can't run them for too long, apart from the noise, things do like to cool.
Same goes for cables. Older cables (paper-lead) could be run in over
load for several hours (like 50%+ overload). "Plastic" cables aren't
as tolerant - they melt.
You also need to keep an eye on road temperatures, some cables have
to be de-rated if the roads are running too hot. Overhead lines are
so much easier, they just sag under heavy load........