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Relay Creation and Innovation

Disturbances in power to large commercial facilities have proven to be incredibly problematic as electric powered equipment and sophisticated building infrastructures have become reliant on the continuous flow of electricity. Voltage spikes and sags, and severe weather conditions are the leading causes of disturbances to electric power in Calgary’s buildings, having had an impact on at least three of the city’s major facilities in the span of one-year. Continuous flow of electric power has been recognized as essential to the larger buildings of Calgary in order for their regular operations to go uninterrupted.

In order to provide the most reliable utility supply to Calgary’s buildings, the power system often employs redundant utility sources via a transfer scheme that switches from a preferred to an alternate source in the event of a power upset. This transfer is anticipated to occur within a few seconds in order for operations to continue accordingly. However, in 2007, as disturbances continued to make their impact and power was unsuccessfully restored within the anticipated few seconds, many buildings were lead to evacuate. Numerous high rises in downtown Calgary were using archaic technologies that were inadequate for modern power system requirements. With this, REV recognized the need for a more reliable protection and control design.

REV has always prided itself in utilizing the most innovative technologies. These technologies offer more robust protection and provide advanced performance characteristics. With backing from Brookfield Property Management and Oxford Properties, REV was commissioned to design a new 25kV transfer scheme that would improve these continual issues with the transfer of power. It was important to create a design that would meet current utility requirements, provide enhanced protection features and send feedback to building operators.

After consultation with Schweitzer Engineering Laboratories, Inc. (SEL) based in Pullman, Washington, the design was created using a powerful and flexible microprocessor-controlled protective relay. The design soon turned into what is now called the SEL-351 Directional Overcurrent and Reclosing Relay and is widely used at utilities and substations around the world.

Specific features of the design include:

  • Extensive monitoring, protection, communications and automation features
  • A selectable preferred source, automated and synchronized transfer to a second source in case of power sag or other disturbance
  • Remote alarm notification to the building engineer staff, should there be a loss of the standby (secondary) source
  • Overcurrent protection and lockout features
  • Ease of installation and flexible programming

No Calgary building owners that had the SEL-351 installed have since experienced any malfunctions in the transfer of power and therefore no building evacuations.

REV was later nominated for and won the BOMA (Building Owners and Managers Association) award for the Calgary area because of this innovative and useful design.

Project Details




In the past, power to large commercial facilities has been unreliable and known for disturbances. Calgary’s downtown buildings were in need of innovation to create continuous power flow.


In order to improve power flow to large commercial facilities in Calgary, REV designed and developed an innovative transfer scheme to stop disturbances. This transfer scheme, named the SEL-351 Directional Overcurrent and Reclosing Relay is a technology that is now widely used at utilities and substations around the world.


+Engineering +Equipment Modernization +Commissioning