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Power Distribution Center Design, 2.4kv Switchgear And MCC Replacement

The Challenge

A Mont Belvieu, Texas, Fractionation Facility was operating a 2.4kV electrical distribution system using 40-year-old outdoor switch gear and motor control centers. The company desired to replace and upgrade this lineup with new-generation switchgear and motor control technology that meets current design standards and preferred engineering practices.  Replacement 2.4kV equipment design was based on vacuum contactor technology, a completely isolated low- voltage control cabinet, and microprocessor-based protective relays.

ONEOK Hydrocarbons Southwest, LLC selected M S Benbow & Associates (MSB) to provide professional engineering services.  MSB was contracted to write specifications and provide engineering and design expertise to provide a complete IFC Demolition and Installation Drawing Package to replace the outdoor 2.4kV equipment lineup. MSB also served as a project engineer and project manager.

The electrical system would be designed for continuous and reliable operation, with an emphasis on operator safety and ease of maintenance.

The Solution

ONEOK elected to replace the existing 2.4kV switchgear and motor control center and house the equipment in an elevated environmental-controlled Power Distribution Center (PDC) to provide climate control and remove flood hazards.

MSB wrote the specifications for both the new 2.4kV lineup and the PDC.  MSB wrote the Issued For Bid packages, sent it to selected vendors, evaluated their responses, and provided that information to ONEOK for vendor selection.  MSB assisted ONEOK in Purchase Order construction and provided oversight and review services of vendor drawings packages and technical issues.  As the process developed, design changes were made and implemented under the direction of MSB.

As the design team for ONEOK, MSB was also responsible for developing Factory Acceptance Test (FAT) procedures for the 2.4kV equipment and the new PDC.  They participated in the FATs as well as the commissioning and startup of the new system.

MSB developed a complete Demolition & Installation Drawing Package for the project, including:

  • Civil & Structural aspects of the job:
    • Number and types of building support piers
    • Number and types of cable tray bridge support piers
    • Concrete spread footings for stairs, landings, and tray supports
  • Electrical infrastructure:
    • PDC and cable tray grounding plan
    • Cable tray system
    • Power and control cable design and routing plan

Due to an unforeseen land use variance issue late in the design process, the client had to relocate the PDC building site from its planned location, requiring a redesign of the entire civil, structural, and power distribution scheme from the PDC to the loads.  MSB assigned additional resources to the job to meet the compressed project timeline.  This scope change involved extensive coordination between MSB and site contractors to meet deadlines.


The Outcome

The new 2.4kV power distribution system is designed to meet the most current design standards and preferred engineering practices, including vacuum contactors and micro-processor protective relays.  The new elevated PDC building is air-conditioned and well-lit.  It includes a state-of-the-art fire alarm system including an HVAC Shutdown Panel.  The building was designed for future equipment expansion.

ONEOK has replaced old technology (40-year-old outdoor electrical gear) with new state-of-the-art gear.  Reliability, operator safety, and maintenance issues are markedly improved.

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