Looking for Trouble

Power distribution at an education institution is pretty simple: Don't go down — ever.

On campus, uptime is money. Students expect the lights to be on and the HVAC system to be working when they show up for class, and so do the parents paying many of the bills. In research laboratories, students and faculty invest massive amounts of time in projects that truly could change the world, and it takes an uninterrupted flow of electricity to prove or disprove academic hypotheses.

Circuit breakers are the linchpin of an institution's power-distribution system, so it's not surprising that several warning signs of an aging system relate to these devices. These include a steadily increasing amount of breaker nuisance tripping or failure of a main breaker after it has been unused all summer.

When warning signs occur, it's a message to facilities managers and administrators that breakers may need to be upgraded to help the power-distribution system meet existing and future needs. But fears of extended periods of downtime to complete an upgrading project, along with the ramifications for students and faculty, often stand in the way.

Will your circuit breakers keep your institution up and running? If you're not convinced that they will, are you prepared to make decisions about upgrading them?

Replacing and retrofilling

An electrical-distribution system is similar to a car. When it's new, except for routine maintenance done by an on-site electrician or an electrical contractor, it doesn't require a great deal of attention or maintenance. But loads increase over time, through expansion and other factors, and equipment, such as circuit breakers, ages. Nuisance tripping and minor outages become more common, translating into increased maintenance costs that strain budgets.

But more ominous is the possibility of a campuswide power outage. Suddenly, an entire system upgrade — including new equipment purchases, short-circuit coordination and revision of the institution's interconnection diagram, along with downtime and all the related labor issues — is needed, requiring several months of time and millions of dollars to complete. And that doesn't begin to cover the potential negative publicity.

Replacing or retrofilling decades-old circuit breakers to take advantage of the benefits of today's devices can go a long way in modernizing a system. It also can help avoid the problems associated with removing old switchgear and replacing it with new equipment. For example, fused switches and circuit breakers have provided arc flash protection in the past, but now breakers that provide high interrupting ratings without fuses — up to 200,000A at 508Vac — have been introduced. Such breakers eliminate problems common to fused switches and breakers, including hazards associated with changing fuses and the need to stock and replace fuses, along with dependence on related mechanical hardware that requires maintenance or replacement. Plus, they are built to trip faster in order to protect equipment and workers, and typically feature a smaller footprint than fused breakers.

Today's breakers also can feature trip units that act as a communications interface and provide power metering and monitoring capability. This enables facilities-management staff to communicate with breakers, gather power information, monitor events and even remotely control them. The trip units also can be tied into an all-campus, power-monitoring system. If the breaker trips, an alert can be sent to facilities managers with details about its location.

Best of all, replacement and retrofilling options don't require a major time commitment. Replacing a breaker, for example, can result in a short 15- to 20-minute outage. A retrofill process is a bit more extensive and can take eight to 10 hours per breaker section, but that is more desirable than a complete system upgrade.

Following is a primer regarding replacement and retrofill processes for LV and MV circuit breakers at an institution:

  • Replacement circuit breaker

    A replacement LV or MV power circuit breaker is a new breaker that uses a modern modular drawout assembly, designed and tested to interface with components inside the existing switchgear's breaker compartment. An MV replacement breaker is simply a like-for-like replacement that requires no interface to rack into the existing cubicle. With the LV upgrade option, a new cradle interface is inserted into the existing breaker compartment. The cradle design typically includes a new racking mechanism, safety interlocks, primary and secondary disconnecting devices, truck-operated contact (TOC) mechanisms, a new breaker compartment door and other provisions.

    A replacement LV or MV power circuit breaker matches the original breaker in form, fit and function, and is designed and tested in accordance with ANSI C37.59 and C37.09 standards. Because a number of breakers manufactured more than 50 years ago are still in operation, but no longer are supported, the replacement breaker provides education institutions that have older switchgear a viable alternative for increasing performance and reliability. Over the years, upgrades may have left education institutions with equipment from several different original equipment manufacturers (OEMs).

    Another key benefit of LV breaker replacements is they enable facilities managers to exchange older breakers for one common breaker that is interchangeable throughout a power-distribution system. They also allow for equipment upgrades without scheduling a bus outage.

  • Circuit breaker retrofill

    An LV or MV circuit breaker retrofill entails the replacement of the old breaker and related compartment components, such as the stationary primary and secondary disconnects, cell interlocks and racking mechanisms, with a drawout circuit breaker and cradle of a modern, previously qualified design.

During the retrofill design and installation, the existing switchgear cell is modified and equipped with a new drawout cradle assembly. Significant changes are made to the structural components of the existing circuit breaker compartment, as well as to the line and load bus structure and bus bracing. New isolating barriers are installed to conform to the latest electrical switchgear industry standards.

Because the retrofill installation always requires a complete switchgear shutdown, some education institutions take this opportunity to carry out a wider scope of switchgear upgrades. For example, during a planned outage, protective relays often are replaced with new solid state or digital technology. New control features are added, and a power-monitoring system is installed, as well as a new communication network.

An LV or MV circuit breaker retrofill is employed when and where education institutions can afford modifications that require extended switchgear shutdown (minimum eight to 10 hours). When the available fault current is higher than the withstand capabilities of the existing circuit breaker, a retrofill or replacement can upgrade the capacity of the existing system. In such cases, the entire switchgear bus structure and bus bracing must be evaluated and upgraded, which requires the switchgear to be de-energized during modifications.

The retrofill solution also is recommended for breakers exceeding 2,000A continuous current rating because of primary current path interface complexity and the significant temperature increase generated by the primary conductors. Because breakers above 2,000A typically are the main breakers, they always require a bus outage, which makes a retrofill solution as advantageous as a direct replacement.

Both replacement and retrofill options are preferred over switchgear replacements because they do not disrupt the existing footprint of the current equipment, thus avoiding testing of cabling and potential modification to the building housing the switchgear. Modernizing switchgear through upgrade options is done at a lower cost and significant reduction in downtime. Institutions are migrating to more time between outages, as well as shorter outages. Therefore, extending the life of replacement equipment is a top priority.

Observing the signs

Facility managers facing the warning signs of an aging power-distribution system should consider commissioning a facilities audit. Such a study includes evaluating the entire electrical infrastructure and can indicate if replacement or retrofill options are appropriate, or if a more extensive upgrade is recommended. It also can suggest measures to enhance a system, such as a power-monitoring system, which can generate data that can be analyzed to increase energy efficiency and plan future energy usage.

When the appropriate corrective action is determined and bidding is complete, facilities managers and administrators should consider factors beyond cost when choosing a provider. Some manufacturers, for example, are very adept at servicing equipment from their competitors in addition to their own and can custom-build a particular breaker and use it as a replacement or in a retrofill.

The bottom line, however, is to act if warning signs are present. Facility managers and administrators that ignore warnings are risking higher costs, extended downtime and maybe angry stares from students and faculty.

Rice is director, Square D Services, for Schneider Electric, Palatine, Ill.

In with the new

Top five benefits of replacement circuit breakers:

  • Enhanced electrical system reliability.
  • Less cost and downtime compared with new equipment installation.
  • Reduced maintenance and operating costs.
  • Available for most manufacturers' LV and MV ANSI switchgear.
  • Various digital trip devices for short-circuit and overload protection.

Top five benefits of a circuit breaker retrofill:

  • Reduced cost and downtime for equipment upgrades compared with new switchgear installation.

  • Cost-effective electrical system upgrade.

  • Continued electrical system integrity during upgrade.

  • Need for obsolete or unavailable spare parts eliminated.

  • Switchgear upgrade can be expanded beyond the circuit-breaker compartment.

NOTABLE

15 to 20

The number of minutes an electrical system experiences an outage when replacing a breaker.

8 to 10

The number of hours (per section) it might take to retrofill an electrical system.

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