50/50 vs 100/0/100 Loading

[mbrooke]

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

 

[Hv&Lv]

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

 

[mbrooke]

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

Why do you ask? I don't have numbers on hand.

 

[mbrooke]

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

One down side is you can't do automatic throw over on that 2x system scheme we talked about

 

[Hv&Lv]

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

 

[mbrooke]

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

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.

 

[Hv&Lv]

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.

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.

 

[mbrooke]

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.

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.

 

[Hv&Lv]

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.

Like I said, two to three hours.
thunderstorms have customers out of power longer

 

[mbrooke]

Like I said, two to three hours.
thunderstorms have customers out of power longer

True- but I still don't fully like the idea.

 

[Hv&Lv]

True- but I still don't fully like the idea.

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.

 

[mbrooke]

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.

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.

 

[Hv&Lv]

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.

Simply...

 

[mbrooke]

Simply...

Some POCOs are doing that soley on increasing permissible load rating of each substation.