Unit Substation without secondary disconnect tap rule

[live2learn]

I have a 13.2kV to 480Y277V 1000kVA unit substation with a fused main disconnect on the primary side. There is no secondary disconnecting means for the transformer and it is tapped a total of 9 times. I thought you could only tap it 6 times?

 

[augie47]

(a) Is this a utility transformer or customer owned ?
(b) Do all the taps terminate in the same area ? same building ?

 

[don_resqcapt19]

How are the taps protected? They must be protected per one of the rules in 240.21(C). The number of taps will be limited to 6 by the rules in Table 450.3(A) unless this is a supervised industrial installation.

 

[jim dungar]

For decades, well into the 90's, it was common practice for industrial unit substations (direct bus connection transformer to feeders) to be supplied with more than 6 devices.

This is still allowed under 240.92(C), although I do not see it being used much on new construction (it definitely is not favorable to arc flash mitigation),