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Planning For Plant Expansion: A “How-To” on Electrical Substations

Expanding an electrical substation can present challenges, but careful planning, collaboration with the utility, and choosing the right equipment will ensure a successful outcome.

Directory 2016
Lately, the name of the game in manufacturing has been modest growth, with most executives feeling cautiously optimistic about the industry’s outlook. The U.S. Industrial Production Annual Average Index was up 4.2 percent as we entered 2015, and similar increases are expected in 2016 and even 2017. In fact, a recent report indicated that manufacturers had elevated their revenue forecast for the next 12 months to 5.3 percent. And six in 10 industry leaders indicate that they are positive about the domestic economy.

Opportunities are growing as the market continues to improve in the United States. And that growth means companies are considering new lines of products or simply ramping up production of existing lines. Expansion of manufacturing facilities is often the best way — or the only way — to achieve those business objectives. But even with the many benefits of expansion, it can be more complicated than starting fresh with a new facility.

A particular challenge is the expansion of an electrical substation in order to support a larger manufacturing facility. Substations transform voltage levels coming from a utility to provide appropriate levels of power to a facility. When expanding a substation instead of building a brand-new one, many companies run into challenges. Often, plans were not made (or insufficient plans were made) for a future substation expansion during design and construction of the original facility. Therefore, it is often discovered that the available space indoors and outdoors may be limited and constrained, and companies may be forced to expand the switchgear building and transformer yard, or even build a completely new substation in another part of the plant.

Of primary importance, safety and reliability should define any electrical substation and be kept in mind throughout the planning and design process. I ran into such a situation when providing engineering services for a steel manufacturing company. The company had been in operation for several years, and decided to install a new, larger electric arc furnace, which required the addition of a new transformer, new outdoor switchgear, and new indoor switchgear. The outdoor substation was completely full, so it was necessary to expand the substation area to accommodate the new equipment. This expansion required the relocation of a road and utilities, additional grading and fill material, and extensive coordination with the electric utility. The project required careful planning in design and construction to allow the plant to continue operation, while keeping personnel safe during the construction activity.

In order to get started on the right path toward a successful substation expansion, I have learned there are six preliminary steps to follow:
  1. Estimate necessary capacity — Assess the processes and equipment required for an expanded plant and use that information to help determine how much additional power will be needed. That data will then help determine what additional substation equipment, like switchgear and transformers, will be needed, and will serve as the basis for your initial discussions with the utility.
  2. Identify the reliability requirements — Evaluate your manufacturing processes and decide how an electrical outage would impact your operation. If there are critical process areas, you may decide to provide redundant power service (like a double-ended substation), back-up engine-generators, or uninterruptible power supplies for that area. Some manufacturing companies request the utility to provide two independent services to provide an increased level of reliability.
  3. Collaborate with the utility — The next step is to work with the local utility to make sure that sufficient power is available to support a larger substation. It is essential for the utility to know about the details of the project and be fully on board with supplying additional electricity. The utility may have to increase the wire size of its service or even add a new transformer off-property to increase the available capacity. But a solution can almost always be identified by proactively working together.
  4. Evaluate the space — Most substations at industrial facilities have an exterior section that includes transformers and other equipment that connects to the utility, as well as an interior section that includes switchgear that supplies power to the plant. Before any further plans can be made, it is essential to evaluate the physical space available for expanding both indoors and outdoors. Finding adequate space may initially seem like an impossibility, but there is usually a way. I am familiar with projects that required the purchase of land across a street to accommodate the expanded substation. Sometimes finding a solution just takes a bit of creativity. Also, consider whether the original substation and its expanded counterpart will be tied together or kept separate. There are advantages and disadvantages associated with both scenarios, and each substation’s unique needs will help determine the answer. But remember that if one of the substations were to shut down or malfunction, a good design will ensure the other could keep running — that is a distinct advantage.
  5. Conduct a power study — This fifth step may be the most important. A power study should be performed to determine how the additional equipment and power system protection devices would interact with the utility. The utility’s capacity for things like short-circuit current, voltage stiffness, and harmonic content must be taken into account. Cables and transformers must be able to withstand short circuits and maintain the current and voltage within a target range when applying load. And if the plant generates a lot of harmonics, it is imperative to make sure it does not exceed the utility’s limit on harmonic content. All equipment specified should work within the operating parameters.
  6. Choose the appropriate technologies and equipment — Now is the time to choose the right equipment to accommodate load and operating conditions, as well as the right technologies to go inside the substation. Some questions to ask to help steer you toward the right equipment are:
    • Does the plant require arc-resistant switchgear? Are there other ways to mitigate the arc-flash hazard?
    • Will it be necessary to interface the new equipment with existing equipment in the substation? For example, some older types of switchgear are no longer made, meaning modifications may be necessary to accommodate both new and legacy equipment.
    • Will the transformers used be dry-type, oil-filled, or less flammable fluid-filled? Each technology has its plusses and minuses.
    • What type of relays will be used? Commonly used digital relays are sufficient, but there are new types available that meet IEC 61850 standards and are compatible with smart grid technology being implemented at some utilities.
Of primary importance, safety and reliability should define any electrical substation and be kept in mind throughout the planning and design process. Sizing things appropriately in order to operate well within equipment ratings creates the ability to back-feed critical loads in the case of transformer or equipment failure.

Such projects are certainly not easy, but they will become increasingly common as the economy rebounds and manufacturing companies become more competitive. By following the six steps outlined above and working with a qualified engineering firm for proper guidance, industrial manufacturers should be on their way to a successfully expanded plant and the profit gains that go along with it.

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