Not a Natural Habitat
This problem would be hard to find until it is too late without having an effective electrical preventive maintenance program in place. Periodic internal inspections would catch this condition before the conductors and the enclosures were damaged from rodents gnawing, corrosive excrement, or shorting of terminal from nesting materials. This enclosure invasion can be cleaned up, but it is equally important to seal off all penetration points to prevent a recurrence. One missing knockout closure may be all that is needed to allow rodents to access the internal electrical components.
Monday Morning Production
Some electrical problems are not immediately recognizable during a visual-only inspection. This problem was discovered after using infrared thermography to view the connections while under load. When one of three conductors was observed to be “cold” on a 3-phase balanced load, the system was deenergized and looked at more closely. This new cooling tower, variable-frequency drive (VFD) came from the factory with one conductor terminated onto the conductor insulation that was never stripped.
An Obvious but Critical Mistake
Periodic visual inspections of busway include paying close attention to the bolted compression splice clamps. Many manufacturers of busway use a double-headed bolt whereby the outer head snaps off with a wrench at the initial installation. The outer bolt head is designed to snap off at the proper applied torque to avoid needing a torque wrench. The two red washers seen on the bolt heads in this photo indicate that the bolts have never been tightened. The red washers are designed to fall away after the heads are snapped off. This busway has been energized for many years with both splice bolts loose. A visual inspection found this mistake and initiated corrective actions before a potential major arcing event could occur.
No Moving Parts but Still Requires Maintenance
In some cases, the outside environment tries to invade the electrical equipment. In this case, the electrical equipment is invading the surrounding building environment. Fluid leaking from these transformer bushings is getting out of the electrical equipment and contaminating the concrete floor. A quick visual inspection of this installation is all that it takes to establish a corrective action-plan. Without a formal electrical preventive maintenance program, what would compel someone to enter these often forgotten spaces? What damage could result from a low oil condition? What is the cost to repair these leaks now compared to a fire, catastrophic failure, and collateral damage in this space?
Maintaining Environmental Barriers
Sometimes your own processes can invade the electrical enclosures. This can happen from improper NEMA type enclosure selection or from failing to properly secure the enclosure doors or knockout closures. The combustible dust collection in this fused switch can insulate the conductors and affect the conductor heat dissipation. High moisture in the dust can make the contaminants electrically conductive, causing short circuits, arcing, and equipment damage.
The Clock is Ticking to a Major Electrical Outage
This is a common occurrence with many types of electrical equipment — long-term exposure to excessive moisture or active leaks. The source of water could be roof leaks, chilled water lines condensing on the equipment, plumbing supply or drain line leaks. In this case, water has been leaking on the top of this busway and busway switch for a very long time. Once the corrosion penetrates the top enclosure steel, water will run directly onto the busway splices and cause phase-to-phase and phase-to-ground arcing. These failures usually result in arcing ground faults that destroy several 10-foot sections of the busway. Fires and fire-sprinkler water damage also commonly occur and can cause significant business interruptions.
“It’s Always Been Like That”
Some improper electrical installations are very obvious. High-tech equipment or IoT sensors are not needed to pick up on this installation issue. Vertical busway installations are vulnerable to failures due to joint damage from leaks penetrating the enclosure and contaminating the closely spaced busbars. The NEC requires curbs around busways where they penetrate floors. Although spring mounts are used in this installation, it looks like hard cementitious material abuts the busway enclosure. Will the busway spring mount function properly when the busway is bonded to the floor? Will this stack of blocks move up and down with the spring mounts?
An Electrical Industry Concern
The white conductor insulation on this 2-pole breaker shows signs of overheating. The insulation is black and burned at the breaker screw terminal. This damage can be seen during a close visual inspection. If thermographic inspections had been used as part of the periodic EPM, this failing breaker or termination would have been seen much sooner before the insulation became heat damaged. This panel is a Federal Pacific Electric (FPE) Stab-Lok panel that should be scheduled for replacement due to potential electrical and fire safety issues. Read “Old Circuit Breaker Panels Pose Danger” for more information about FPE Stab-Lok panels.
Damage Is Occurring Where You Least Expect It
Visual inspections should include checking panelboard connections where the breakers spring-clamp onto the panelboard busbars. The integrity of these connections can be checked using periodic infrared thermography. These damaged busbars were discovered while working on other nearby failed electrical components. Unchecked failures of this type usually advance to a catastrophic panelboard loss due to phase-to-phase and phase-to-ground arcing faults that melt sections of all three of the busbars. Melting of the steel enclosure typically occurs before the overcurrent protection opens the circuit. Although the arcing initially starts at one phase, the initial ionized air and arc plasma quickly conducts to all of the other phases and ground.
You Can’t Judge A Switch by Its Cover
Sometimes electrical equipment looks perfectly fine from the outside. You might assume that if the outside is clean, then everything inside must be okay too. In reality, this is a perfect example of why periodic visual inspections are so critical to the reliability of electrical equipment. Spiders can get into enclosures through holes in enclosures that are small and normally do not present any unwanted access problems. When dirt and moisture collect on these spider webs that bridge phases and provide paths to ground, conditions are ideal for flashovers and arcing ground fault damage. Arcing ground faults and products of combustion can contaminate adjacent switchgear sections. Long lead times for new switchgear can create unrecoverable business losses.
Some electrical problems are from self-inflicted wounds. Who is allowed to do electrical work at your facility? Are they electrically “qualified” per the NFPA 70E definition?” Would a truly qualified electrician install a copper wire in place of a proper fuse? If unqualified personnel are performing electrical work in your facility, they are exposed to serious danger. In addition, their unsafe acts may cause injury to others who work nearby or are affected by their improper electrical installations. Regardless of how this installation occurred, routine and periodic inspections can discover problems and allow corrective actions to be taken before a fire, injury, or equipment damage occurs.
Improper Field Modifications = No Motor Overload Protection
Visual inspections should always include checking that the motor overload protection is set properly based on the motor nameplate amps and the manufacturer’s setting instructions supplied with the overload relay. Originally, the two IEC motor starters and overload relays in this panel were identical. One of the motor controls was replaced with a different unit that does not have a settable range to protect the connected motor. Motor overload relays that have an adjustable range of amp settings can easily be set to a value that will provide no overload protection for the motor. NEMA type motor overload relays with one overload heater element per phase cannot be changed without physically replacing the three heater elements. These are less likely to be accidentally set to the wrong amp values.