Flood level design criteria for a substation

[cuky2000]

We are preparing a conceptual design for a 138 kV were the area has been determined to be designed for a flood level 16 ft above grade. The options considered are:
1. Floodwall and design the AC yard at grade level with a draining pump.
2. Raise the yard with for 16 ft and build foundations on top of the grade.
3. Raise the grade to 8 ft and allow the waterflood up to the bottom of the insulator (8 ft above foundation/grade)
Please help us with your comments particularly for option 3.

 

[thermionic1]

Curious what the plans are for the control building? We had a major flood some years ago and it was the control building that suffered the most damage. This was a 100 year flood, as I heard it.

 

[dpc]

We have used an option similar to your #3. But as mentioned, we did raise the control building such that it was entirely above the 100-year flood level. This required a significant concrete structure in a seismic area, not to mention quite a few stairs to climb. But assumption was that the transformers, substation structures that support the bus as well as the breakers, regulators, etc, could be partially submerged.

 

[stevenal]

1. Keeping the pump powered during the times it's most needed sounds like a challenge.
2. We've used this option when only a few feet was required. 16' sounds like another challenge.
3. Too much equipment damage. Breakers, transformers, and their control cabinets sit at lower levels.
4. Acquire land on higher ground. We're in the process of moving a low lying flood prone substation presently.

Those 50 and 100 year intervals seem to be coming around a lot more frequently lately.

 

[cuky2000]

Thanks for the feedback.
The most sensitive part including the control room and other rooms are 2 food above the 100 years flood level.
We suspect that selectively raising the location for the 138 kV equipment is the first choice but there is a probability that the water ill is close to the insulator during the flood scenario.
I guess the maintenance of energized facilities during floods should be avoided for safety reasons. If done, should be with a dead-bus. Any thoughts?

Below are some of the preliminary ideas.

 

[itsmoked]

I'd put the equipment at 16 so any deeper than 16 feet starts using your equipment sides. Not less than than the 16 foot. I'd put the control room starting at 18 feet. It's all calculations loaded with guesses that get you the 16ft and as stevenal suggests a hundred years is no where near a hundred years in 2020 years. I'm in a state that has been choking in smoke for weeks and weeks now. Last year for the first time ever it was about 3 days. We were burning more forest in a day than we used to burn in a year. Every year is worse than the last. Don't bank on only 16 feet.

Wind or a boat wake or a current can easily stack a few feet on that 16ft level.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[OffTap100]

Only option #2 seems to address the real issue. Completely relying on pumps or letting the sub flood to bushing height is a fools errand. Ask New Orleans about this.

OT100

 

[cuky2000]

To add more challenges to the proposed site, we learned that there will be building a tank farm with 4M gallons. Obviously this is another point to make this site less attractive. "So far two strikes and two outs".

Any suggestion on how to evaluate the risk of having a facility next to a potential fire hazard?

 

[stevenal]

Have you considered GIS? I have no experience with them, but gas tight should likewise be liquid tight.

 

[davidbeach]

GIS might keep water off the power conductors, but there’s a significant amount of control and monitoring equipment around any GIS installation that would not do well under water.

 

[cuky2000]

Hi Stevenal,
GIS may be an option. For this application, the space saved by the GIS is limited since there are 3 air/SF6 bushing. Also GIS has local cabinets and the air bushings has to be treated as any open air insulator.
This site also has a lousy soil and the flood wall option need to be built on piles adding significan cost and the concern of rely in pumps for water infiltration and other incidental water in the yard is a concern for this option.

 

[stevenal]

I understood you had a control room above flood level already. Might need to expand it or add another. Easier to put controls 16’ above grade than an entire station.

 

[DTR2011]

ABB worked with Con Ed after Hurricane Sandy and had some creative solutions.