# 4 service entrances, one building



## Magnettica (Jan 23, 2007)

For the last 8 work days, I've worked in an old building built in 1929. It's 8 floors high, and the length and width of an entire city block. It has 4 service entrances. Two of them are rated at 13,200 volts direct from the substation. From there, their are several transformers rated at 4160 on various floors throughout the building. I've never worked in a building bigger than this so my question is, is this how power is distributed in newer building like this one?


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## brian john (Mar 11, 2007)

A newer building MIGHT have the 13.8 KV, maybe with a double ended SWBD with open tie either manual or automatic operation, distribution at 13.8 KV to fusible air break switches feeding dry type 13.8KV Delta to 408/277 VAC Wye dry type transformers, then distribution at 480/277 and 208/120 Vac as necessary.

In switchboards such as these check the batteries utilized for system operation, if they look bad REPLACEMENT IS A MUST. Check the battery voltage and the battery charger. Typically if there are 60 cells the voltage should be 135 VDC (float at 2.25 VDC per cell). Most but not all HV gear utilize 60 cell (lead acid) or 90 cell (nicad, float at 1.5 VDC) 120 VDC (NOMINAL) 135 VDC float and 138-140 VDC equalize for control.

Relays if used for OCP must be tested, the air switches and CB need regular maintenance, insulators require cleaning. This work is typically completed by a QUAL:IFIED testing or expieenced HV firm.


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## Magnettica (Jan 23, 2007)

brian john said:


> A newer building MIGHT have the 13.8 KV, maybe with a double ended SWBD with open tie either manual or automatic operation, distribution at 13.8 KV to fusible air break switches feeding dry type 13.8KV Delta to 408/277 VAC Wye dry type transformers, then distribution at 480/277 and 208/120 Vac as necessary.
> 
> In switchboards such as these check the batteries utilized for system operation, if they look bad REPLACEMENT IS A MUST. Check the battery voltage and the battery charger. Typically if there are 60 cells the voltage should be 135 VDC (float at 2.25 VDC per cell). Most but not all HV gear utilize 60 cell (lead acid) or 90 cell (nicad, float at 1.5 VDC) 120 VDC (NOMINAL) 135 VDC float and 138-140 VDC equalize for control.
> 
> Relays if used for OCP must be tested, the air switches and CB need regular maintenance, insulators require cleaning. This work is typically completed by a QUAL:IFIED testing or expieenced HV firm.


Well I certainly hope an HV firm does this sort of work because after reading all that my head is spinning! :no: But thanks for all the info.\


By the way, is 13.2KV an ancient voltage rating that's no longer used because 13.8 is more efficient?


Is there a reason for it at all?


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## MDShunk (Jan 7, 2007)

When I hear someone saying "Thirteen-Two", that's sorta the same as hearing someone still saying "One-ten". Popular standard voltages for distribution are 4.16kV, 4.16Y/2.4kV, 12.47kV, 12.47Y/7.2kV, 13.2kV, 13.2Y/7.62kV, 13.8/7.97kV, and 34.5kV. Depends on where you live as to whether "thirteen-two" rings well in your ear or not.

With the exception of the 34.5, most (maybe 90%) of distribution is in the 15kV class, so it's the same set of skills for pretty much all of those voltages.


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## Magnettica (Jan 23, 2007)

Thanks for that explanation!

I need to take a power generation course!


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