Contents
Overview
Electrical inspections are the most commonly known and practised infrared application. The benefits are obvious, since electrical failures can easily cause personnel injury and death, equipment damage, material loss, and downtime.
Unfortunately, this familiarity has made many maintenance personnel and thermographers dangerously casual in their approach. It is too easy to simply pick a camera up and go looking for "hot spots." While it is true that any substantial temperature rise between phases should be treated as a high priority repair, there is a lot more to electrical infrared thermography.
One important factor is the load on a component. The load exponentially affects the power in a circuit and the resulting temperature rise. A small temperature difference under a load of 1A may be crictical under a load of 20A. There are still many maintenance personnel and professional thermographers who do not correlate load and temperature rise, and this causes a false sense of confidence when serious problems still exist. The load or temperatures are not always referred to in following samples, but that information was used in determining the criticality of the faults.
It is also important to understand the theories involved in how infrared radiation works and how heat transfer is affecting the objects in a thermal image. Concepts such as emissivity, thermal reflections, thermal conductivity, and indirect temperature measurement are crucial to the identification and diagnosis of electrical problems.
Although infrared electrical inspections are often carried out for insurance purposes, thermography's true value is as an integral part of a predictive maintenance program. Combined with other technologies and performed conscientiously, thermography will have cost benefits that vastly outweigh the costs.
Anyone performing infrared electrical inspections has to remember what is at stake, and make the effort to do the job properly. The risk of serious injury, death, or huge loss of profit inspired us to pick up the camera in the first place, and the identification of a few "hot spots" will not eliminate that risk.
1. Electrical Survey: MCC
This image shows loose connections on the load side of a contactor (B and C Phases), and loose connetions on the terminal block (B and C Phases).
You may left-click on the picture for an expanded view.
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2. Main Electrical Room: Fuse Block
This image shows a loose fuse retaining clip on the fuse block for the power supplies and heat station water system panel in a facility's main electrical room. Amps A phase=20, B phase=20, C phase=20. The temperature rose to 96°C. Manual inspection, cleaning, and tightening of all connections and fuse clips was recommended as well as the replacement of any required components.
You may left-click on the picture for an expanded view.
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3. Back-up Power Supply Batteries
When batteries are your first line of defense in the case of power loss, it is vital that they perform on demand. This image shows a failing cell on the lower left side (high temperature differential indicated in red). If a problem like this is left unattended, critical systems could be left without power.
You may left-click on the picture for an expanded view.
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4. Transformer Cabinet Terminal Block Connections
During an infrared survey of a plant substation, Maverick found these loose connections on the terminal block in a transformer cabinet.
You may left-click on the picture for an expanded view.
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5. Lighting Panel
This image identifies loose connections, an overloaded circuit, and a faulty breaker on this common type of electrical panel. As with all electrical problems, the resulting failures could have serious consequences for the equipment, property, and personnel involved.
You may left-click on the picture for an expanded view.
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6. Extruder Control Panel
This image shows the main control panel for an extruder. The thermal anomally noted here is on the fuse block on the right hand side of the lower left fuse block. Temperatures rose to over 100° C in this area. Inspection, cleaning, and tightening of all connections and replacement of any required parts was recommended.
You may left-click on the picture for an expanded view.
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7. Typical Fault Conduction Pattern
This is a typical conduction pattern, showing a thermal tapering along the coated electrical cable from the electrical connection. The connection, likely the source of the fault, does not appear to be as hot because of the emissivity differences between materials. Phase A is under a load of 67.8A, compared to 70.8A and 70.4A for B and C respectively. There is a 30° C temperature rise between phases. This is definitely a critical fault that requires immediate attention.
You may left-click on the picture for an expanded view.
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8. Contactor
All three phases are under a load of approximately 61A. There is a very critical temperature rise across the phases of at least 45° C. This temperature measurement is conservative, since it is an indirect temperature. The source of the resistance is likely the electrical contact inside the plastic housing on the A phase.
You may left-click on the picture for an expanded view.
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9. Fuse Disconnect
All phases are under a load of 32A. Between the B and C phases, there is a temperature rise of at least 11° C. There are a lot of apparent temperature differences, such as the cooler reflections off of the shiny surfaces, which have to be disregarded.
You may left-click on the picture for an expanded view.
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10. UPS Inverter
Both sides of this UPS inverter are under a load of approximately 120A. There is, however, a 25° C temperature rise on the neutral side. The temperature measurements were performed on the cable insulation rather than the shiny connections, since the shinier surfaces mostly reflect cooler, background temperatures.
You may left-click on the picture for an expanded view.
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11. Mystery Wire
This wire was on a 15A breaker. It was under a load of 16A. Since the breaker and wire were unlabelled, and no one knew what the circuit powered in the manufacturing facility, there was no way to know if this was the full operating load. Although there was no critical temperature rise or electrical fault, this was still a potentially serious maintenance issue.
You may left-click on the picture for an expanded view.
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12. Lighting Panel
Three circuits on this lighting panel were not fastened to the panel bus bar. There are electrical faults to be found on lighting panels, however, all of the covers must be taken off to properly identify and diagnose the problems.
You may left-click on the picture for an expanded view.
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13. Rectifier Cabinet
The two wires in this rectifier are under a load of 5A - 6A. The left wire, which appears cooler, is actually under slightly greater load. There is, however, a temperature rise of approximately 11° C between the two. The temperatures were taken from the wire insulation, not from the shiny connections, in order to eliminate errors due to background reflections.
You may left-click on the picture for an expanded view.
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14. Microwave Station Rectifier Breaker
The wire coming out of the bottom of the breaker is over 100° C. This is a very critical fault. The insulation will be breaking down and losing its insulating qualities. The temperature of the actual faulty connection inside the breaker is higher, although there is not as serious of a thermal signature on the plastic breaker housing. This is an example of an indirect infrared diagnosis.
You may left-click on the picture for an expanded view.
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15. Connection on Manufacturing Control Panel
This image shows a small electrical connection that was loose and subject to wide load fluctuations under normal operating conditions.
You may left-click on the picture for an expanded view.
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16. C Phase on Disconnect
The C phase of this disconnect was exhibiting a serious temperature rise under normal operating conditions. This electrical equipment was critical in the operation of furnaces on a chemical production facility.
You may left-click on the picture for an expanded view.
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17. Compressor Fuse Disconnect
All three phases of this fuse disconnect had a load of approximately 160A. The center phase had a temperature rise of approximately 75° C. The fuse was replaced and the fuse connections tightened, but this only made the external temperature signature more pronounced. This electrical equipment was connected to a compressor that was critical to the operation of the entire manufacturing line at this strandboard facility.
You may left-click on the picture for an expanded view.
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18. Extension Cord Short
This extension cord was being used to power an air conditioning unit inside of an electrical connection cabinet in the pit of a manufacturing facility. The cord end pictured here was inside the closed cabinet. A short is apparent.
You may left-click on the picture for an expanded view.
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19. Loose Neutral Screw
The neutral screw in this electrical panel was very loose. The threads were stripped, and the connection had to be made elsewhere.
You may left-click on the picture for an expanded view.
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When batteries are your first line of defense in the case of power loss, it is vital that they perform on demand. This image shows a failing cell on the lower left side (high temperature differential indicated in red). If a problem like this is left unattended, critical systems could be left without power.
During an infrared survey of a plant substation, Maverick found these loose connections on the terminal block in a transformer cabinet.
This image identifies loose connections, an overloaded circuit, and a faulty breaker on this common type of electrical panel. As with all electrical problems, the resulting failures could have serious consequences for the equipment, property, and personnel involved.
This image shows the main control panel for an extruder. The thermal anomally noted here is on the fuse block on the right hand side of the lower left fuse block. Temperatures rose to over 100° C in this area. Inspection, cleaning, and tightening of all connections and replacement of any required parts was recommended.
