A Broad Overview of Electrical Maintenance of Switchgear and Circuit Breakers

January 27th, 2016

Switchgears and circuit breakers exist in basically every building with electricity and they play a particularly important role in industrial settings. Manufacturing plants and similar facilities tend to use a lot of electricity, meaning breakers play a key role in regulating power flow and preventing failures. When circuit breakers and switchgears do fail in these buildings, catastrophes can ensue.

Dan Crawford, group manager for field engineering at mutual insurance provider FM Global, has seen more than his fair share of breaker failures and knows the kind of damage they can do. FM Global operates in 148 countries, employs around 1,800 engineers and strives for consistent, practical, scientifically proven, cost-effective solutions for its clients. For an insurance provider, it's in FM Global's best interest to provide its clients with best practices regarding plant maintenance

Crawford gave a presentation at 2015's Reliable Asset World II in Clearwater Beach, Florida, outlining his company's stance toward reliability centered maintenance. Crawford offered his expertise on how to best manage several risk factors.

"When circuit breakers fail, their malfunctions are hard to overlook."

Major repercussions involved
When circuit breakers fail, their malfunctions are hard to overlook. At the low end, a blown circuit box can cause a power outage, result in downtime and require a maintenance professional to repair or replace the equipment. On the other end of the spectrum, switchgear and breaker malfunctions can result in major fires, explosions and, in the worst case, injury and facility closure. Beyond the loss of the switchgear itself, there is also the effect the failure had on the controlled equipment and the source of the ignition to contend with.

The frequency of failures depends on factors such as environment, operator training, age and history of the equipment, maintenance and operating conditions. The severity of the failure will vary based on operator training, safety devices and the presence of a contingency plan.

Fortunately, those are conditions that are by and large under the company's control. By making a commitment to accident prevention, facility managers can avoid such setbacks. Crawford identified three primary tools managers can use to engender a safe workspace with regard to circuit breaker and switchgear malfunctions:

1. Make a contingency plan
Best to avoid a breakdown, but sometimes the best laid plans can go awry. In the event of a malfunction, facility managers should have detailed steps in place to mitigate damage. Here is what they need to ask themselves:

  • Are spare parts on-hand and ready to install? If critical equipment is damaged, best to have a new replacement that's in good shape ready to take its place.
  • Is it possible to re-configure the electrical system? If so, it might be possible to get the facility back up and running without completely repairing the circuit, thereby avoiding costly downtime.
  • Is any redundant equipment installed? A double-ended substation offers a backup plan when a piece of equipment goes offline.
  • Have you identified an alternative supply? Consider renting a diesel engine-driven generator.

2. Install safety devices
To prevent employees from injury caused by circuit breaker failures, it's important to have safety equipment installed wherever possible. That includes smoke detectors, circuit breakers, warning signs and any other devices that can warn those in the area of a malfunction.

3. Create a preventative maintenance program
The first two points are necessary in case of an emergency, but with the right maintenance program, maintenance engineers should be able to avoid the majority of electrical mishaps in the first place. Electrical protection is a system that consists of many components – any one of them could fail, triggering a chain of events and a serious problem. The best maintenance plans leverage periodic checks based on data that indicates how frequently different components are expected to fail.

This requires managers to keep a running log of maintenance activity, observed failures, equipment status and so on to accurately predict when a component may fail and take steps to avoid catastrophe – either by replacing it or repairing it. For example, in the case of a flooded lead acid battery, maintenance professionals may want to check for evidence of corrosion or leaks on a monthly basis, the temperature of 10 percent of the cells on a quarterly basis and the specific gravity of all the cells on an annual basis.

Electrical malfunctions can cause serious injury.Electrical malfunctions can cause serious injury.

Real-world examples
To illustrate his point further, Crawford highlighted two case studies that both demonstrated the need for all three circuit breaker failure prevention and damage mitigation tools outlined. With that said, in both situations, the lack of an adequate preventative maintenance program ultimately allowed the failure to occur.

In the first case, a manufacturing facility with 24/7 operations and running off utility power alone experienced an explosion and fire involving 480 volt cabinets, as well as a tank rupture of a mineral oil-filled transformer. With a contingency plan in place, the facility experienced minimal downtime. However, a lack of maintenance led to those malfunctions – a switchgear battery discharged and a circuit breaker seized. Fortunately, there was no combustible load in the electrical room, so no fire followed the failure.

In the second case, another plant was also in operation 24/7 using utility power. Here, a bus bar failed, an aluminum bus and steel frame enclosure vaporized, the suspended ceiling blew off, and hot particles from the bus duct explosion ignited combustible material above the ceiling, causing a fire. A complete plant shutdown followed, and smoke and water caused serious damage to the food product. An investigation revealed the ground fault protection did not function and there was no recorded maintenance that would have identified an issue. The same was true of the 480 volt bus bar. With better predictive maintenance across the board, the plant could have avoided that shutdown and all the damage to its product.

By incorporating predictive maintenance strategies into a plant's electrical plan, maintenance professionals can prevent the facility from undergoing serious electrical failures that can have disastrous consequences. Just some basic preparation can be effective, but a comprehensive plan is necessary to completely preserve plant production.

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