IEEE 2014 T&D Conference Paper 14TD0564 - Storm & Flood

Hardening of Electrical Substations

Co-Authors: J. M. Boggess, IEEE Member

G. W. Becker P.E., Senior IEEE Member M. K. Mitchell P.E., IEEE Member

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FORUM 2 | Transformers, Substations and Switchgear Forum

Room: W185BC, Paper: 14TD0564

Tuesday, April 15, 2014 1:00 PM – 3:00 PM

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Storm & Flood Hardening of Electrical Substations

Source: NOAA (National Oceanic and Atmospheric Administration)

Top 5 US Costliest Storms $125B - Katrina (2005) $68B - Sandy (2012) $38B - Ike (2008) $29B - Wilma (2005) $27B - Andrew (1992)

Tertiary Source: Wikipedia, for background purposes only

U.S. 2012 BILLION-DOLLAR WEATHER AND CLIMATE DISASTERS Recent superstorms have increased pressure on utilities and governmental agencies to harden critical infrastructure for improved grid system reliability during major storm events.

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Storm & Flood Hardening of Electrical Substations TYPICAL SUBSTATION SITE DESIGN

• This methodology is feasible for most substations (i.e. inland or non-critical).

• However, critical substations and/or coastal substations may have unique risks.

• Industry standard substation site design is to avoid significant impacts from flooding at the 100 Year Flood Elevation, plus 1 foot.

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Storm & Flood Hardening of Electrical Substations

Impacts to substations can range from minor to catastrophic:

Substation owners must evaluate the risk of loss for specific equipment and/or systems to determine the scope of the flood mitigation.

FLOOD INUNDATION IMPACTS TO SUBSTATIONS

• Loss of HVAC System

• Loss of AC Station Service

• Communications Failure

• Loss of DC battery system(s)

• Water Damage to Protection, Automation

& Control Equipment (i.e. Control House)

• Damage to High Voltage Equipment from Flooding in Switchyard

• De-energization of a Substation

• Fire and Catastrophic Loss

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Storm & Flood Hardening of Electrical Substations DEVELOPING A FLOOD MITIGATION STRATEGY

After identifying critical substations with vulnerability to storm surge (as per FEMA FIRM maps) or high flood zones, different levels of flood mitigation can be employed.

Innovative substation solutions can provide early warning capabilities, mitigate potential outages, and reduce restoration times during weather events.

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Storm & Flood Hardening of Electrical Substations SUBSTATION FLOOD MONITORING

Float switches can be strategically installed at locations throughout a substation. The output contacts from the float switches can then be hardwired into the substation’s SCADA system and monitored via status points to alert operations of flood events.

Multiple float switches, at different elevations, can notify operators of initial flood conditions, as well as higher water events at critical flood levels.

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Storm & Flood Hardening of Electrical Substations ELEVATING SUBSTATION EQUIPMENT

For distribution substation applications, a proven approach has been to combine the cost-effectiveness of modular equipment solutions with the storm hardening concept of elevated substations.

At medium voltage levels, many modular substation designs are available that can be installed on elevated foundations, platforms or stilts.

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Storm & Flood Hardening of Electrical Substations ELEVATING SUBSTATIONS

• Based on prior installations & case studies, elevating substations with “indoor” GIS (gas-insulated switchgear) has proven to be an excellent solution to flood-prone substation locations.

• Elevated substations, integrated with GIS, provide reliable, reduced-footprint replacement solutions with “environmental immunity”.

According to the U.S. DOE, per August 2013 Report - U.S. Energy Industry Response to Recent Hurricane Seasons, “Common hardening activities to protect against flood damage include elevating substations and relocating facilities to areas less prone to flooding.”

Elevating an entire transmission substation is more challenging due to the amount of space required for increased electrical clearances at higher voltages.

• Typically utilizes an enclosed cast-in-place (CIP) basement/cable vault, partially below grade, with water-proofing, sloped-floor, and sumps to manage water intrusion. For severe flood loading, stilt designs or breakaway walls can be incorporated into the foundation design per ASCE 7-10 flood loading guidelines.

• HV apparatus, protection & control, and other major equipment is located on the first floor concrete diaphragm with an elevation above projected flood levels.

• A pre-engineered metal building, with increased galvanizing and specified with HDG or stainless steel materials, are used to withstand the corrosive environment.

• Excellent flexibility can be provided with SF6-to-Cable connections.

Storm & Flood Hardening of Electrical Substations KEYS TO ELEVATED GIS SUBSTATION DESIGN

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Storm & Flood Hardening of Electrical Substations CONCLUSIONS

• Significant storm surge and flood events are relatively rare. However, recent superstorms have caused catastrophic property damage and loss of life.

• The U.S. DOE estimated outage costs to range from $18 to $33 billion dollars per year (in the last ten years). Paramount to the significant costs related to these power outages is their potential hindrance to emergency responders.

• Infrastructure hardening with substation upgrades at strategic locations can reduce the impacts of flooding & wind at critical substations during severe weather events.

• Innovative substation solutions and new technologies can improve grid storm hardening by detecting floods early or building substations with environmental immunity to withstand flooding, corrosion & wind.

• Storm & flood hardening of critical substations vulnerable to flooding can provide improved reliability, life cycle costs, security and most importantly public safety.

THANK YOU!