Short Circuit Calculation when Power Company provides Max Available Fault Current

[Jaldir]

So I received a Bldg Dept comment requesting short circuit calculations for a roadway lighting project. This is the first time I've been asked for this in over 20 years of roadway lighting designing. The power company provided the following information:
Max Available Fault Current at the transformer secondary terminals is 53205 symmetrical amperes at 120/240 volts.
The protective device on the line side of the transformer is a 25-amp type KS fuse.
The primary service voltage is 13.2kV L-L.

The lighting panel board will be 100 amp, 120/240V single phase

What is the correct method of calculating the short circuit amps for the given condition?
Thanks in advance for your help.

 

[augie47]

I would likely use their number and the Bussman fault current program

Fault current calculator

A mobile app and web-based application for determining the fault current of single- and three phase systems with fuse selection and conductor sizing guides.

www.eaton.com

 

[MyCleveland]

So I received a Bldg Dept comment requesting short circuit calculations for a roadway lighting project. This is the first time I've been asked for this in over 20 years of roadway lighting designing. The power company provided the following information:
Max Available Fault Current at the transformer secondary terminals is 53205 symmetrical amperes at 120/240 volts.
The protective device on the line side of the transformer is a 25-amp type KS fuse.
The primary service voltage is 13.2kV L-L.

The lighting panel board will be 100 amp, 120/240V single phase

What is the correct method of calculating the short circuit amps for the given condition?
Thanks in advance for your help.

How have you been selecting the AIC & SCCR of your OC devices and equipment over these 20 years ?

 

[Jaldir]

No. This has never been a requirement. Shop drawings are usually reviewed/approved by the maintaining agencies. Lighting plans have generally always included voltage drop calculations, load center calcs, and photometrics.

 

[MyCleveland]

No. This has never been a requirement. Shop drawings are usually reviewed/approved by the maintaining agencies. Lighting plans have generally always included voltage drop calculations, load center calcs, and photometrics.

No...this has ALWAYS been a requirement. It has, and ALWAYS will be the engineers requirement. Not the ECs, the equipment vendors EE staff, the inspector, the plan reviewer or any one else (many others will plug in here), but your job as person selecting the equipment and subject to the energy parameters (as obtained from the providing utility) the electric equipment is exposed to.

 

[augie47]

I am shocked that you had jibs go thru plans review and inspections without someone looking at the available fault current and the AIC ratings of the equipment.

 

[electrofelon]

No. This has never been a requirement. Shop drawings are usually reviewed/approved by the maintaining agencies. Lighting plans have generally always included voltage drop calculations, load center calcs, and photometrics.

So who exactly specifies the electrical equipment, specifically the circuit breakers? Have they just been guessing at the AIC values?

 

[jim dungar]

No. This has never been a requirement. Shop drawings are usually reviewed/approved by the maintaining agencies. Lighting plans have generally always included voltage drop calculations, load center calcs, and photometrics.

Section 110.9 and 110.10 have been in the NEC for the 50 years or more.
Over that time these sections have been 'ignored' so often, additional sections have been added.

The NEC does not care who does the actual calculation and equipment selection but these are clearly 'design level' activities, which I feel are the responsibility of the engineers stamping the drawings for the feeders and panels. They are not typically included with the lighting fixture photometrics themselves.