California Substation - ASCE 113 vs CA Building Code

[structural-eng]

I have been designing the steel and foundations for wind and solar substation across the country for 10 years now and am very familiar with the previous version of ASCE 113. We just got the new version of ASCE 113 last week so I'm working on understanding the changes. Our client for substations is an electrical engineer that does both engineering only and EPC projects and they have recently started working in California. We have a project in Sacramento County where the county is requesting that the drawings list the current building codes that will be followed for the project on the permit drawings. We have always just listed the ASCE MOP 113 on our drawings because that is what we have been designing with but the county specifically references the California building code. I understand that the Substation Design Guide is just a guide and that the building official ultimately has authority to enforce whatever they want but I have also been doing this long enough to know that MOP 113 is THE design standard in the industry. I’m wondering if anyone has any suggestions as far as helping explain to the county official that the building code is intended for buildings and structures for the purpose of life safety and the substation is equipment located in what is typically considered unoccupied space and therefore the life safety standards aren’t appropriate.

 

[dauwerda]

This is a good question and as far as I know doesn't have a good clear cut answer - it is unfortunate that currently it seems to boil down to the building official deciding what to enforce here. (I would love to be proven wrong on this statement).


If you are trying to go down the path of showing through the codes why the IBC (I will be referencing that rather than the state specific CBC, which I am assuming is similar) isn't relevant to substations (which more and more seems to be trying to apply itself to everything, it's definition for structure is "that which is built or constructed" which is basically everything), here is the best I can do:

Section 105.2.2:
A permit shall not be required for the installation, alteration or repair of generation, transmission, distribution or metering or other related equipment that is under the ownership and control of public service agencies by established right.

I would argue this is somewhat excluding substations from the scope of the IBC​

Substations and transmission generally fall under the NESC (per state and federal regulations) not under the IBC as I show below:

Section 2701 of the IBC:
The provisions of this chapter and NFPA 70 shall govern the design, construction, erection and installation of the electrical components, appliances, equipment and systems used in buildings and structures covered by this code.
(This is including NFPA 70 as the electric code essentially)

NFPA 70 Article 90.2 makes the following inclusions:
- Yards, lots, parking lots, carnivals, and industrial substations
- Installations of conductors and equipment that connect to the supply of electricity
- Installations used by the electric utility, such as office buildings, warehouses, garages, machine shops, and recreational buildings, that are not an integral part of a generating plant, substation or control center

and it makes the following exclusions:
- Installations under the exclusive control of an electric utility where such installations are governed or regulated by FERC, FCC, or state regulatory commissions (this is paraphrased)

So, the IBC includes/adopts the NFPA 70 as the electrical code and the NFPA specifically excludes substations (though includes industrial substations) and goes on to state that substations fall under state regulatory commissions. Those state and/or federal regulatory commissions specify the NESC as the code/standard.

The NESC has the following to say about the structural portion of substations:
101. Scope

Part 1 of this Code covers the electric supply conductors and equipment, along with the associated
structural arrangements in electric supply stations, that are accessible only to qualified personnel. It
also covers the conductors and equipment employed primarily for the utilization of electric power
when such conductors and equipment are used by the utility in the exercise of its function as a
utility.​

(underline emphasis by me)

110.C Electric Equipment

All stationary equipment shall be supported and secured in a manner consistent with reasonably
expected conditions of service. Consideration shall be given to the fact that certain heavy
equipment, such as transformers, can be secured in place by their weight. However, equipment that
generates dynamic forces during operation may require appropriate additional measures.​

162. Mechanical protection and support

A. All conductors shall be adequately supported to withstand forces caused by the maximum short-circuit
current to which they may be subjected. Where supported conductors extend outside the
electric supply station, such conductors and their supports shall comply with the grades of
construction, strength, and loading requirements of Part 2 of this Code.
NOTE: For further information, see IEEE Std 605™-2008 [B36].​

IEEE 605-2008 7.5 Structure Design

Design the support structures to withstand permanent and exceptional loads on them. The calculation methods are presented in Clause 10, the loads to consider in Clause 11, and the strength and other considerations in Clause 12.​

IEEE 605-2008 10.2 General mechanical design procedure

To design a bus structure:
...
b) Evaluate the loads applied on the bus structure.
c) Combine these loads in a statistically coherent manner since they cannot generally all happen at the same time. The load combination may be determined by utility design standards or published guidelines applicable to substation bus structures.
...​

The NESC also states:
010. Purpose

...
C. This Code is not intended as a design specification or as an instruction manual.
​

So, the NESC does not give specific design criteria for substation structures, it basically just says they need to be adequate. It points to IEEE 605 for short circuit bus design and IEEE 605 points to "published guidelines applicable to substation bus structures", i.e. ASCE 113 (which wasn't published yet at the time that IEEC 605 was published)



Other pertinent sections that allude to the exclusion of substations from the typical building codes:

IBC Section 1613.1:
...
Exceptions:
...
4. Structures that require special consideration of their response characteristics and environment that are not addressed by this code or ASCE 7 and for which other regulations provide seismic criteria, such as vehicular bridges, electrical transmission towers, hydraulic structures, buried utility lines and their appurtenances and nuclear reactors.

ASCE 7(C32.5.4.3)states: "Substations and grids are outside the scope of ASCE 7."

 

[cranky108]

Or are you talking about the substation building? Not in CA, but have had problems with that, specifically that we call it a building, and not a control enclosure. The differences are in the details.
Buildings require ADA restrooms, and others. while control enclosures do not. Also details about livability, where enclosures don't.

 

[structural-eng]

As far as I know, we are being asked to design the entire substation to meet the requirements of the California building code (not just the control house). I have asked if it's possible to talk to the building official to get clarification but I haven't been told I can yet. I have heard about problems with building officials wanting ADA and such on control houses on other projects and our client has switched to calling it a control enclosure to help mitigate that.