Modern power delivery system infrastructure contains technology that monitors and controls power, which improves data collection, communication, safety and reliability. These features let plant personnel improve operational efficiency by reducing the number of unplanned outage events and minimizing downtime if an event does occur.
In many older facilities, however, these capabilities do not exist, because legacy electrical switchgears, transformers, and other pieces of equipment that are long-wearing and expensive to replace are still in use. Fortunately, many cost-effective options exist to retrofit older equipment with modern components.
When preparing for system upgrades, vendor selection is crucial. Ideally, the vendor selected will have a staff that is experienced, trained and knowledgeable in designing retrofit projects. In all cases, an upgrade project should include:
- Budgeting for hardware, software and labor.
- Development of a project schedule and careful outage planning for the upgrade.
- Design of the system and procurement of all components prior to the outage.
- Labor and logistics planning for the outage to ensure that work is completed on time.
- Testing of all critical components prior to the outage.
- Failure mode and effects analysis (FMEA) to plan for challenges during the outage and prepare solutions or workarounds.
- Site safety and work policy that includes lockout tagout training and documentation.
An experienced project manager with a background in power systems is indispensable. Many facilities operate continuously with infrequent planned outages. Careful planning and execution is required to maximize work and re-energize systems in a timely manner. To be successful, create a detailed schedule and work procedures. For example, plan types and skill sets of labor required and procure all materials well in advance. During procurement, be meticulous and consider smaller items such as personal protective equipment and installation components. Small details missed in outage planning can create schedule slippage, safety risk, or technical errors while also limiting the amount of work accomplished.
When possible, select technical solutions that minimize electrical and mechanical installation labor during the outage. Pre-engineered or “packaged” kits minimize labor, the potential for human error during installation, and commissioning time. These kits typically include the components necessary to install new devices such as breakers, trip units, and relays into older vintage electrical equipment enclosures like switchgear cubicles.
Budget constraints frequently limit the scope of modernization projects. Therefore, it is important to maximize the reuse of existing infrastructure. For most electrical distribution systems, some of the larger components—including switchgear cubicles, transformers, trays, conduits, cables and buses—can remain in place while upgrading smaller but key components such as breakers, trip units, protective relays, and the programmable logic controller. Fortunately, many of these smaller components frequently can be replaced in older electrical equipment, providing the technology and features necessary to improve data gathering, communication, safety, and reliability.
Electrical systems are typically custom-engineered for each site. Available options must be defined and evaluated for a given plant because a wide range of upgrade options exist.
Following is one example of a completed GE customer installation that has yielded improved system performance.
Generator protection upgrades
Numerous generation stations and cogeneration plants protect generators with older generator protection relay systems, which can be difficult to maintain or unreliable. Specifically, in plants built in the power generation construction boom of the 1990s and early 2000s, many units are protected by early versions of digital protection relays (DGP); these relays are now reaching their end of life. Relays with more-advanced technology have superseded the early versions.
Relay protection schemes tend to be custom-engineered for sites, and different product models have different dimensions and electrical terminal layouts. Therefore, a redesign project can require extensive panel and wiring modifications. However, in the case of the DGP relay, a G60-based relay kit exists that physically fits into the existing panel space and has identical external connection points. Generation and cogeneration plants are realizing the benefits of this type of upgrade path, including:
- Quick installation, without the need to rewire dozens of control wires.
- Software directly converts the configuration files for the original relay to the new relay format without programming.
Several customers along the Gulf Coast have upgraded to the latest technology in generator protection to improve performance and gain access to new features. Some of the benefits for upgrading these legacy systems to new relays include:
- Additional features and multiple existing components can typically be retired and replaced with a single unit.
- More communication and protocol options.
- Software that contains more features for storing and analyzing data.
A DGP replacement upgrade was recently completed at a cogeneration facility in Texas during a three-day planned turbine outage. Retesting of existing instrumentation as well as all input and output points was included to insure that the entire protection system—complete with new and existing components—was fully functional.