Examining the Nuts and Bolts of Substation Construction

By Kathleen Davis, associate editor

In October, Utility Automation & Engineering T&D spoke with Pete Ivey, vice president of Southern Company Transmission Design and Construction, about the when, where, why and how of new substations in their region.

Southern Company Transmission is the business unit of Southern Company that plans, designs, constructs, operates and maintains all the company’s transmission assets.

UAE: How much is Southern Company�s transmission unit investing in substation construction this year, approximately?

Ivey: Southern Company’s substation capital budget for 2006 is approximately $200 million.

UAE: Is there a particular place in your region that needs more TLC than others?

Ivey: Almost all sites require some TLC. But in particular the north Georgia area, the area in and around Atlanta, the area around Birmingham, and the coastal areas of Alabama, Georgia, Mississippi and the panhandle of Florida are experiencing rapid growth at this time. To maintain the reliability of our system, we will be expanding our line and substation infrastructure in those areas over the next several years.

UAE: What factors lead Southern Company to consider adding a new transmission substation to the grid? Too much load? Potential development?

Ivey: For transmission substations, there are two main drivers: load growth-either from increased usage by existing customers or new customers locating in an area-and the addition of generating facilities.

UAE: Are there options you consider before deciding on the full-blown plan of constructing a substation? Pad-mounted transformers, perhaps?

Ivey: There are a lot of options we look at, such as:

  • Adding capacitors in existing substations or out on the lines.
  • Reconductor of existing transmission lines.
  • Increasing the capacity of an existing substation by replacing the transformer.
  • Installing a second transformer in an existing substation.

Option selection depends on several factors, such as impact to the public, forecasted load growth in the area, the capacity of existing facilities, and the cost/benefits of the solutions.

UAE: How long does planning usually take and what does that process entail?

Ivey: For a transmission substation, we typically expect to have about a three- to five-year lead time prior to the substation beginning service. The lead time is driven by the transmission line right-of-way requirements and land acquisition processes involved. There can be multiple new transmission lines involved and the substation site has to be acquired early enough to allow the new lines to be routed and rights of way to be acquired. For very large or extensive projects the lead time needed can stretch out even further.

UAE: What are the most important considerations during the construction of a new substation? Cost? Location? Structure?

Ivey: Our philosophy can best be described as striving for best overall value. We want to evaluate our projects based on a variety of factors and identify the optimum balance to maximize their total value.

These factors include:

  • Safety: The safety of our employees and the public is our No. 1 priority. Consequently, safety is the most important aspect of constructing a substation. Our substations are designed and constructed to meet NESC code requirements-to ensure that the work environment is safe for our employees and to provide the necessary safety features for the public.
  • Public acceptance: We want to be good neighbors in the community and expect that the appearance of our substations should fit in with the surrounding area.
  • Cost: This is always important because we have a responsibility to our customers to control our costs so the rates they pay continue to be among the lowest in the country.
  • Maintenance: Our facilities are designed for a long service life. We take into account requirements associated with maintaining the facility over its lifetime.
  • Location: This has a big effect on our costs, as well as an impact on the final appearance of the facility and our long-term ability to maintain the facility and replace damaged equipment. Factors considered in siting new substations include location of existing transmission infrastructure, proximity to load centers, and impact to the public.
  • Structures and equipment: The type of structures and equipment we use are typically our standard structures and equipment we use all over our system. All operating company transmission groups (including Alabama Power, Georgia Power, Gulf Power and Mississippi Power) have worked together to develop common standards for equipment, materials, design and construction practices. This allows us to purchase in larger volumes and also control the parts and equipment we must maintain on hand in order to restore service when something is damaged by outside forces such as lightning, tornadoes, hurricanes, vandalism, etc.
  • Access: Our employees visit substations regularly to inspect, maintain and repair equipment. Their ability to drive into and out of substations accident-free is important, in addition to the obvious needs relative to maintenance/repair.

UAE: How do you partner with equipment vendors and contractors to complete a substation project?

Ivey: We have developed alliances with several equipment manufacturers to provide the high-quality equipment we need at a reasonable price. Southern Company will own, operate and maintain the substations we design and construct for a long time in the future. We consider more than the initial cost of the equipment; we look at the long-term cost of owning the equipment as well.

We use contractors throughout our system for various activities based on the work load demands. This allows us to handle the peaks in our work load without adding additional full-time employees whose services would no longer be needed when the work goes away. We often use contractors to complete design projects, grade and prepare substation sites, construct substations, install equipment in existing substations, maintain equipment, and maintain the substation sites. Having a third party perform work for us in a satisfactory manner requires that they have a very good understanding of our expectations.

Insurance, Risk and Those Pesky Transformers

One item that comes up often with the practice of erecting a new substation is insurance and risk mitigation. Utility Automation and Engineering T&D asked a couple of industry experts to discuss how those issues factor into the construction process.

Terrence Lee, senior staff engineering specialist for international insurance company FM Global, has worked for the company for more than 13 years providing technical guidance for electrical equipment and systems.

Lee discussed the company’s belief in the prevention and control of losses through engineering.

“The conceptual, planning and construction phase of a new substation is an ideal time to put loss control measures in place,” he said.

“These same loss control measures would cost substantially less if incorporated into the design of a substation compared to the same loss control measured if they were implemented after the substation is completed,” he added, giving the example of controlling the fire exposure presented by oil-filled transformers.

Lee continued, “By properly separating transformers at the construction phase, we can avoid the need to build fire barriers or to install water deluge systems for these transformers.”

Transformers are often a major issue when dealing with risk mitigation and construction, according to the Lee and industry vendor Cooper Power Systems.

Lee reported that, during a five-year period, FM Global clients incurred 582 transformer losses totaling close to $300 million. Of these losses, 34 transformer failures resulted in an explosion and fire, while remaining losses only resulted in failure of the transformer.

“The utility industry accounts for nearly half of the transformer losses reported to FM Global,” he said.

Additionally, the company found that transformer windings are the leading cause of failures, where 60 percent of reported losses were caused by insulation failure of the transformer windings. Insulation failures can occur as a result of old age, operating and environmental conditions, overvoltages and poor design.

Lee added, “Currently, FM Global is designing a method to determine when transformer windings are vulnerable to failure due to old age.”

Arvind Chaudhary, staff engineer with Cooper Power Systems, knows all about transformers. The company specializes in a number of industry products, including insulating dielectric fluid for transformers.

Chaudhary believes the use of insulating fluids that possess biodegradable and high flashpoints that do not require large catchments for oil spills, as well as the use of safety margins in the selection of equipment are two ways in which companies can factor in insurance and risk mitigation during the planning and construction of substations.

He stated, “The use of these fluids-and switchgear with arc flash withstand characteristic-should help impact insurance concerns and finance.”

And those concerns should be addressed throughout the construction process, according to both of our experts.

Lee stated that FM Global works with a client from the beginning, providing “input at the conceptual stage and throughout the construction phase of a new substation.”

Lee added that concerns cover a wide range of issues, including a look at the location of the substation to ensure that it is not exposed to natural hazard perils like flood, earthquake, windstorm and bushfires.

“If there is no option but to build in a flood-prone area, FM Global will recommend flood mitigation measures such as raising the entire foundation above the 500-year flood level, not designing any below grade areas like cable basements, installing flood walls if it is not practical to raise the foundations and installing sump pumps if some below grade areas are essential,” Lee explained.

Additionally, FM Global also provides advice on equipment selection-whether the equipment has a poor operating history or unresolved design issues or is, in fact, the perfect fit. They’ll put in a good two cents.

Cooper Power’s Chaudhary also has a bit of advice:

  • Understand client needs and expectations for operation and maintenance.
  • Look at real estate considerations to determine whether open-air or GIS (gas-insulated switchgear) is for you.
  • Look at the possibility of employing modular integrated substation.
  • Engineer to be ahead of the whole process.
  • Consider contingencies (loss of site power etc.).
  • Consider lead time of the equipment.
  • Plan well.
Click here to enlarge image

-Kathleen Davis, associate editor

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The Clarion Energy Content Team is made up of editors from various publications, including POWERGRID International, Power Engineering, Renewable Energy World, Hydro Review, Smart Energy International, and Power Engineering International. Contact the content lead for this publication at Jennifer.Runyon@ClarionEvents.com.

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