50/50 vs 100/0/100 Loading

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mbrooke

mbrooke

Batteries Included
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When designing an N-1 substation, is it better to have two transformers loaded 50% each, or a single hot spare?


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Question with a question...
what are your no load and full load losses in the transformer?
 
No load vs full load losses...

a transformer sitting there doing nothing but being energized is using power resulting in system losses.
you have to weigh the benefit of having one sitting there idle vs the losses with carrying half the load.
FWIW, we have three stations with two transformers each that are 3/4 Loaded at max demand.
i wouldn’t consider 50/50.
I would get a bigger transformer.

we have a spare on the yard that can be moved to multiple stations.
for emergencies we have mobilesthat can be in operation in about two hours
 
Hv&Lv said:
No load vs full load losses...

a transformer sitting there doing nothing but being energized is using power resulting in system losses.
you have to weigh the benefit of having one sitting there idle vs the losses with carrying half the load.
FWIW, we have three stations with two transformers each that are 3/4 Loaded at max demand.
i wouldn’t consider 50/50.
I would get a bigger transformer.

we have a spare on the yard that can be moved to multiple stations.
for emergencies we have mobilesthat can be in operation in about two hours
Click to expand...


I like and agree with the idea of having two trafos. Why wouldn't you consider 50/50 loading though? It takes time to get a spare in place where is with 50/50 loading you can restore power in a second.
 
mbrooke said:
I like and agree with the idea of having two trafos. Why wouldn't you consider 50/50 loading though? It takes time to get a spare in place where is with 50/50 loading you can restore power in a second.
Click to expand...
How often do transformers go out?
We have a 1954 XF that is still in service.
that’s a lot of capital sitting doing nothing.

we test every five years, so the hope is to catch problems before they get catastrophic.
 
Hv&Lv said:
How often do transformers go out?
We have a 1954 XF that is still in service.
that’s a lot of capital sitting doing nothing.

we test every five years, so the hope is to catch problems before they get catastrophic.
Click to expand...

You're right- and in the past they were often connected directly to the line or busbar via a simple disconnect.

But- when one does fail- I'd hate to see customers go several hours without load to bring in a mobile unit.
 
mbrooke said:
You're right- and in the past they were often connected directly to the line or busbar via a simple disconnect.

But- when one does fail- I'd hate to see customers go several hours without load to bring in a mobile unit.
Click to expand...
Like I said, two to three hours.
thunderstorms have customers out of power longer
 
mbrooke said:
True- but I still don't fully like the idea.
Click to expand...
thats because you don’t have to fund the idea, or explain to your shareholders why there are 30 million in transformers sitting just waiting on one to go out.

if you had to do that you’ll get used to it.
 
Hv&Lv said:
thats because you don’t have to fund the idea, or explain to your shareholders why there are 30 million in transformers sitting just waiting on one to go out.

if you had to do that you’ll get used to it.
Click to expand...

You think shareholders understand electricity? 😛

Or simply implement recloser loops schemes. Load both trafos to 3/4, loose on unit and transfer load to neighboring substations then initiate auto throw over.
 
mbrooke said:
You think shareholders understand electricity? 😛

Or simply implement recloser loops schemes. Load both trafos to 3/4, loose on unit and transfer load to neighboring substations then initiate auto throw over.
Click to expand...
Simply...
 
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