There have always been a handful of methods to draw management's attention — some good, some not so good. Methods involving open flame, billowing smoke or dented vehicle fenders usually fall into the not-so-good category. Those of us at the Bureau of Reclamation were fortunate to have been involved with the Folsom Dam power plant (Folsom, California, U.S.) project as it attracted management's positive attention by saving a lot of money.

In 2005 and 2006, we replaced obsolete protective relays serving three transformer/generator units at the Folsom Dam powerhouse, which is managed by the Central California Area Office of the Mid-Pacific Region, the Bureau of Reclamation and the U.S. Department of Interior, Folsom. The project was designed and presented to management as a modular protective-relay solution that replaced the original electromechanical relays. The new modular solution incorporated a configuration to provide generator, transformer and bus protection. The upgrade protective-relay system was selected and designed in-house by Folsom staff.

PROJECT OBJECTIVES

The protective-relay modernization project had multiple goals:

• Bring all generator and transformer protective-relay hardware up to the latest performance standards

• Reduce long-term maintenance costs and the risk of failure

• UPGRADE SCOPE AND OUTAGE SCHEDULE

  Improve protective efficiencies and capabilities at the Folsom power plant.

To prepare for the project, we first evaluated the available options. We examined the project scope, design options, pre-design and overall estimate for labor and hardware costs. The three units were due for annual maintenance and one turbine runner would require cavitation repairs. The goal was to design a demolition, construction and commissioning plan that would be economical and supportable by the staff, and that-could be completed without having to extend scheduled outages.

The original cost estimate of the project was US$362,000 for the coordination, design and project completion of three units. The final cost of the project was under budget by $33,000, at an average cost of $110,000 per unit. In comparison, a similar two-unit relay-modernization project was completed two years earlier at the New Melones power plant in Calaveras County, California, at an average cost per unit of approximately $220,000 using a different approach. The Folsom cost per unit was approximately half the New Melones cost.

As part of our protection modernization, we defined the project scope to include complete replacement of the transformer and generator protective relays. The existing protection suite (Fig. 1) used discrete electromechanical and analog relays. While the package was state of the art when the plant was constructed, it offered no reporting capabilities other than trip targets. The relays were installed in 24-inch (61-cm) cabinets.

PROTECTION MODULES SPEED INSTALLATION

The upgrade protection package was specified to include dual redundant generator protection and primary transformer differential with independent backup overcurrent protection. All the reporting, availability and performance advantages of the newer generation relays were anticipated.

Today, there is tremendous benefit and incentive to keep capital equipment, particularly generation assets, in service. Significant nonproject cost savings is accrued simply by returning these assets to service on time or early.

The central challenge in this project was to perform demolition, installation and commissioning of the relay systems within the predefined outage windows of 23 days for the first unit, which required turbine runner repairs, and 18 days for each of the subsequent units. A longer outage would represent additional costs in unrealized income due to generator unavailability.

PREPARATION AND INSTALLATION

As we researched approaches for performing these upgrades, our attention was directed to EasiLinc Protection Modules (Fig. 2). The modules were developed as an assortment of prewired protection modules for a variety of applications, including distribution feeder protection, transformer backup overcurrent protection and generator protection. Each module consists of an SEL relay appropriate for the application prewired to ac and dc test switches in a 19-inch (48-cm) sub-panel. The assembly is suitable for mounting in an equipment rack or appropriately sized panel cutout.

A major advantage of the EasiLinc Protection Modules is that each module comes with the relay prewired to its test switches. Module schematics and wiring diagrams also are included. These features speed design, installation and commissioning, and reduce the length of the outage necessary to perform the protection upgrade. The only new field wiring is that needed to connect the module test switches to the existing cabinet terminal-block points.

After reviewing the product and contacting others who had used it, we selected EasiLinc Protection Modules as the basis for the unit protection upgrades.

The Folsom power plant protective-relay replacement effort was one of the most critical jobs undertaken by the staff to date. Prior to the initial outage, we prepared a mock-up of the new front panel sized to fit the existing protection cabinet (Fig. 3). We did this to test the fit and to refine the assembly and handling procedures used in the actual construction.

We then fabricated, painted and assembled the panel that would be installed in the protection cabinet during the initial outage. This panel was equipped with 19-inch mounting rails, the protective-relay modules and all internal wiring (Fig. 4). We also included a pigtail of external wires that would be measured and terminated at installation. This approach allowed the staff to complete a significant portion of the time-consuming assembly work prior to the start of the outage. This proved to be an efficient and effective way to complete this aspect of work, as only half the time would be available to accomplish the same work on the second and third units.