By Bob Fesmire, ABB Inc.
The phrase “aging infrastructure” is getting a lot of use these days, and nowhere is it more evident than in electrical components that have moving parts and that undergo significant physical wear. Utilities across the country are facing a baby boom of legacy equipment that is reaching the end of its designed lifespan, but at the same time their options for maintaining these items are narrowing.
Circuit breakers are a prime example.
Most original breaker manufacturers-if they are even still in business-do not provide support for legacy models past a certain age. Refurbishment and remanufacturing shops have moved in to fill the void left by the original manufacturers, but in some cases there can be quality concerns with breakers not meeting the demands now being placed upon them.
When it comes to circuit breaker maintenance, utilities have a range of options. At one end of the spectrum, they can buy spare parts or remanufactured parts and perform the refurbishment work themselves. There are also combination training/refurbishment programs in which utility engineers are trained to do refurbishment by working on their own equipment. (At ABB, the program is known as “BYOB” or “bring your own breaker.”) The next option, moving upward in cost, is to outsource the refurbishment or remanufacturing operation entirely. And, finally, there is outright replacement.
Obviously, the “refurbish vs. replace” decision comes down to a cost-benefit analysis for the given utility. The availability of parts for legacy equipment, the ongoing maintenance costs associated with sticking with a legacy design, the up-front costs of replacements compared to their reduced maintenance-all of these things factor in. At the same time, other considerations-like the need to up-rate the fault current capability of a particular switchgear without replacing the entire unit-also come into play.
More and more though, utilities are opting for roll-in replacement breakers instead of refurbishment. There are a number of reasons why, which we’ll explore via some examples, but the primary driver is technology. Modern magnetically actuated breakers have fewer moving parts (less than 10, as opposed to 100 or more in conventional spring-actuated breakers), and as a result are virtually maintenance-free. The resulting difference in long-term cost of ownership is compelling, especially to utilities facing steadily increasing maintenance costs across their systems.
Roll-in replacement breakers, as the name implies, are designed to fit in the same cradle or cell as the legacy breaker they are replacing-roll out the old, roll in the new. In this way, they provide the benefits of a new breaker (modern technology, higher performance, lower maintenance costs, greater reliability) while preserving the utility’s investment in the surrounding switchgear.
New technology was a major factor for a large Western utility in deciding what to do about a slow SF6 leak on a legacy breaker on the HVAC system at a major airport. Further maintenance was certainly an option, but the company was concerned about reliability over the longer term, especially for an application like the air conditioning system in the airport terminal. They settled instead on replacement and installed the first magnetically actuated circuit breakers on their system in December 2004.
The experience of another utility in the Southwest with roll-in replacements was more programmatic. The company had already performed an analysis of its breaker fleet and had planned to replace about 30 to 40 breakers each year. However, given the number of breakers on the system, this approach would have meant the company would be replacing breakers in an almost perpetual cycle as older units reached the end of their lifespan. In 2004, the breaker replacement program was accelerated, focusing on new technologies that would significantly reduce maintenance costs and improve reliability.
Roll-in replacements fit the utility’s strategy well and the company set out on a much more aggressive replacement regimen, ordering more than 100 breakers in 2004 and another 156 this year. The combination of speed (in terms of the overall program’s execution), reduced ongoing maintenance costs and reliability meant that the breaker fleet could be upgraded-and the benefits realized-much sooner than previously expected.
In the nuclear arena, the exodus of original manufacturers from the support business is especially pronounced. Circuit breakers that were once supported by the original manufacturer are being supported through other means or not at all. At the same time, new breaker designs by the original manufacturer to fit in the existing equipment have not yet been qualified for use in nuclear plants. A major player in nuclear generation faced this dilemma when it needed safety-related breakers to replace legacy equipment in two of its plants. Opting for cradle-in-cradle replacements, the company is now working with ABB to certify its Emax low-voltage spring-actuated breakers to nuclear standards. With lifecycle testing complete, the breakers are now being put through seismic, software and radiation exposure tests.
These examples illustrate how the technology and cost advantages of replacement breakers are being realized by utilities approaching the question of refurbish vs. replace from a variety of starting points. As the equipment “baby boom” continues to strain budgets, roll-in and cradle-in-cradle replacements can offer both immediate benefits and long-term advantages. à¯£à¯£
Fesmire is a communications manager in ABB’s power technologies division, and writes regularly on transmission and distribution, IT systems and other industry topics.