Seismic Resiliency Consideration for Utilities
By Scott Howard, P.E., Waypoint Seismic and BKI Engineering Services
Natural Disasters Drive Reliability and Resilience Efforts for Utilities
With the rise in natural disasters nationally, communities are increasingly dependent on electric utilities to maintain the electrical grid’s reliability and resiliency. Recent hurricanes in the East are a stark reminder of the damage natural disasters can bring. While the Northwest has not seen hurricanes, we do have exposure to other natural disasters in the form of wildfires, extreme weather, and a potential for significant earthquakes. Accordingly, utilities are investing their often-scarce resources into system hardening to protect their communities.
One area where the significant risk can be mitigated by relatively low investment in seismic upgrades. If you think about existing supply chain issues with material scarcity, high costs, and long lead times for critical equipment, utilities are incentivized to make a relatively small investment in seismic hardening to protect the assets they have instead of losing them in an event. Demand for transformers and other equipment within substations is at record highs now. Imagine what conditions would be like following a disaster. How long will it take to get your system back online after an event when you have no immediate access to replacement components (if you have a spare transformer, you are one of the lucky few)? Earthquakes are inevitable and, depending upon how well a utility prepares, they can either be catastrophic or moderately disruptive to your system. This article will discuss some of the highest risks to our electrical systems and possible ways to increase resiliency to earthquakes.
Understanding the Risk
As seen in the photo from the United States Geological Survey (USGS), much of the Northwest is susceptible to moderate to high-ground shaking from earthquakes. Substation equipment is the most seismically vulnerable part of an electrical system. Keep in mind, it wasn’t until the late 1990s that seismic performance was considered in the design of substation equipment. Even then, not all utilities required equipment design to consider seismic forces. Based on a report from the Department of Energy in 2014, the average age of a power transformer is approximately 38-40 years old of which 70% of power transformers are more than 25 years old. So we can see, our infrastructure has significant vulnerability to large earthquakes and, as mentioned previously, is harder to replace.
Okay, enough with the doom and gloom. So, we know we have vulnerabilities to earthquakes in the United States, but what can utilities do to improve the resiliency of their system?
- Specify that all new equipment is seismically qualified by IEEE 693, Seismic Design of Substations.
- Ensure that all substation structures and their foundations are designed by ASCE 113, Substation Structure Design Guide.
- Provide flexible jumpers between the bus and equipment that accommodates the relative displacements.
- Seismically harden the substation.
These recommendations all require capital to implement, but some are less costly than others and any efforts will help protect assets that may be hard to replace.
The least costly and most immediate way to increase seismic performance is to update equipment specifications to consider the effects of earthquakes. IEEE 693 provides methodologies for substation equipment seismic design. Equipment designed to meet the requirements of IEEE 693 would be considered seismically qualified. IEEE 693 was developed by a group of utility engineers, consultants, and equipment manufacturers that considers the historic seismic performance of substation equipment to develop methodologies for seismic qualification of each type and voltage of the equipment. IEEE 693 provides a prescriptive and widely adopted method to design substation equipment for earthquakes. From experience, the cost increase of the equipment is not significant, and most equipment manufacturers are familiar with the seismic qualification of equipment. If you want to determine the seismic qualification level required by IEEE 693 for nearly all substation equipment, check out the Equipment Qualification Procedure Tool (EQPT) on the Waypoint Seismic website (waypointseismic.com). The EQPT tool is free and provides the required seismic qualification levels and methods for all substation equipment based on the site location, equipment voltage, and equipment type.
Seismically hardening existing substations should be considered in areas of high or moderate seismicity. Some common seismic vulnerabilities of substations include:
|Common Seismic Vulnerabilities and Mitigation Measures|
|No equipment anchorage to the foundation||Retrofit existing equipment with new anchorage|
|Inadequate or no flexible jumpers between equipment and bus||Provide flexible conductors between equipment and bus that allows maximum relative displacement|
|Control building structural and nonstructural components (i.e., cable trays, ceilings, partitions, equipment, etc.) inadequate||Evaluate and retrofit existing structural components and provide seismic bracing for nonstructural components|
The hardening of existing substations should consider the need for outages. In most cases, the existing equipment and control building can be hardened without an outage or impacting operations. Several techniques can be used to ensure the substation can remain operational during hardening. There are too many considerations to list in this article. However, a couple of examples are:
- Provide vibration and dust management when working inside a control house.
- For transformers, welding to a tank could heat the oil releasing gases inside the tank.
Plan and Prepare Now!
What I hope you come away with from this article is the importance of doing something rather than nothing, no matter how small it may be. Without a plan, it is difficult to achieve our goals. Start by evaluating your current substations for seismic vulnerabilities and develop a plan that ranks substation hardening upgrades by importance and cost. Incorporate your plan into capital improvement budgets and look for grant opportunities. If you do, you will drastically improve your recovery time following a seismic event.
Massive Federal Funding for Utilities
To spur investment in our infrastructure and enhance grid resiliency, the Federal Government, with the passage of the Infrastructure Investment and Jobs Act (IIJA) and the Inflation Reduction Act (IRA), has established programs to provide funds for electric utilities. Under the IIJA, a Funding Opportunity Announcement (FOA) for a $2.5 billion program of grants to prevent outages from disruptive events and enhance the resilience of the electric grid (IIJA Sec. 40101c), is in the Draft-for-Comment phase. Once the final FOA is published, utilities can submit a concept paper followed by a formal grant application under this Grid Resilience and Innovations Partnership (GRIP) Program.
Additionally, the Inflation Reduction Act (IRA) of 2022 includes a utility assistance program under the US Department of Agriculture (USDA) for $9.7 billion (IRA Sec. 22004) in rural electric system resiliency funding. BKI is working in partnership with Strategic Marketing Innovations (SMI – DC-based lobbying firm) to help two utilities secure GRIP funding and is happy to talk with other utilities interested in taking advantage of these federal funding opportunities.
BPA Establishes New Procedures for Customer-Owned Meters
On September 15, 2022, new procedures for the set-up and configuration of customer-owned and maintained meters went into effect. The Bonneville Power Administration (BPA) developed these changes with the intent of revising and improving its procedures is to ensure consistent design, testing and maintenance of new or replaced metering equipment to provide both BPA and its utility customers access to consistent and accurate meter data.
Since BPA relies on data from customer-owned meters for billing and load forecasting, BPA implemented these changes. For a more information on these procedures, please check out BPA’s Responsibilities and Technical Requirements Guide for Customer Owned Meters. It shares BPA’s expectations for customer-owned meters (rather than BPA-owned meters) to monitor new projects.
New 2023 National Electrical Safety Code (NESC)
As most utility folks are aware, the 2023 edition of the National Electrical Safety Code (NESC) was published in August of 2022 by the Institute of Electrical and Electronics Engineers (IEEE). The NESC is the national standard for safety in the design, construction, operation, and maintenance of electric and communication systems. This latest update includes many important changes that will impact future electric utility transmission and distribution system designs. BKI’s engineers are actively reviewing the NESC changes to incorporate the new standards into our partner utility designs. Please consider BKI a resource for questions related to these updates.
BKI/URC Has Moved!
At the beginning of 2022, BKI Engineering Services and the recently formed Utility Resource Collaborative moved their headquarters to Vancouver, WA. BKI was in Battle Ground, WA for over 35 years and the time was right to relocate. If you are in the area, please come visit. We think you will like the new space and we would love to see you! As an added incentive, every visitor gets free BKI coffee.