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Preventive vs Predictive Maintenance - The Performance Gap

Preventive vs Predictive Maintenance - The Performance Gap

One of the most common causes of power outages, and a primary cause of electrical arc flash incidents is the rise in temperature of a faulty joint or connection . As equipment ages, faulty electrical connections in LV/MV switchgear, and other electrical equipment can increase; studies show that poorly maintained switchgear is 62% more likely to fail. The accepted “Best Practice’ has, until recently, been a preventive maintenance program in the form of periodic thermal imaging inspections (typically annual), often utilising a combination of an infrared thermal imaging camera and a thermal ‘window’. However, although an evolutionary step onward from reactive maintenance, there remains a very significant "Performance Gap" between the perceived levels of protection, compared to the actual level of risk mitigation, obtained from a preventive maintenance approach.

The difference between preventive and predictive maintenance is that preventive is routine maintenance or inspection, scheduled at regular intervals regardless of equipment condition, thus often incurring unnecessary costs; while predictive maintenance is only scheduled as needed, based on the assets real-time condition. Predictive maintenance, therefore, reduces labor and operational downtime costs, whilst increasing safety by removing people from places of risk, and increasing the life of the asset.

The critical issues which create this ”Performance Gap” situation, while factual, are often not fully explained or understood.

They include:

  • Workers remain exposed to risks
  • Annual thermography represents an inspection of less than 1% of operational time leaving 99% dependent on luck
  • Timing of inspection is often not reflecting the most critical operating electrical loads
  • Measurement is reliant on both equipment & operator skills to correlate to the true internal temperature, ( thus never be of uniform quality)
  • Data remains stand- alone & not integrated rather than dynamically integrated information
  • Transmission rates of IR through a “thermal window” can deteriorate significantly over time -affecting the accuracy of temperature readings

The manufacturers of thermal imaging cameras state that when conducting a thermal inspection of electrical equipment two requirements are essential to obtain accurate temperature data.

  • The first is that the camera must have direct line of sight to the conductor being inspected, (thermal windows have variable and deteriorating levels of IR transmission, thus not meeting this requirement).
  • The second requirement is that the conductor being thermally imaged, must be operating at a minimum load of 40% of design load e.g. if circuit is designed for 3kA, then it must be operating at minimum 1.5kA at time of inspection. This is rarely observed by those carrying out thermal inspections of electrical equipment and is not known by the majority of owner / operators of the equipment.

Fortunately, there is now a way to close this ‘Performance Gap’ and enhance protection, by continuously monitoring and analyzing temperature data; not just identifying, but proactively predicting issues arising from faulty connections. Vendor neutral innovative technology has evolved to provide the "Next Technology Step", of Predictive Maintenance, with 24x7 monitoring detecting approximately 70% more failure symptoms in advance of failure than periodic inspection. This is achieved via permanently installed temperature sensors, specifically designed for thermal monitoring of electrical switchgear, MCC and transformers.

These resolve all the critical issues identified above, and close the "Performance Gap" which exists; thereby providing enhanced levels of protection, safety, operational uptime, and improved asset integrity.

The accelerating global consumer demand for IOT devices and related products, is also fueling the growth of industrial IOT, or IIOT as it is known. This requires industrial equipment and machinery to have embedded condition monitoring sensors, which acquire condition data 24x7, with connection to the internet for subsequent analysis, and real time identification of fault conditions. This enables the most efficient maintenance practice to be adopted, enabling the considerable benefits over the life of the equipment which can be delivered as part of the IIOT / digitization of critical electrical infrastructure. These IIOT benefits include

  • Eliminates unnecessary inspection and associated costs
  • Reduces intrusive maintenance to ‘as required’ by condition of equipment
  • Reduces downtime costs associated with periodic inspection / maintenance
  • Reduces costs of repairs /replacement parts and associated downtime via increased advance detection of failure symptoms
  • Increases safety by removing people from places of risk
  • Identifies best performing equipment for future procurement decisions
  • Provides OPEX savings from reduced on-going periodic inspection / maintenance costs.


This accelerating shift from inspection to monitoring comes as a result of the adoption of digitization strategies by virtually every major Company globally, as they strive to remain competitive in the new digital world.

Modernizing electrical infrastructure to include innovative technologies such as 24x7 thermal monitoring will enhance the safety, performance, and life of electrical infrastructure via predictive analytics. No matter what type of electrical installation, a continuous and digital approach to monitoring will provide the most cost effective and efficient way of ensuring your electrical equipment is protected 24x7, as part of a digitization strategy to remain competitive in the changing digital world.

The COVID-19 pandemic has also led to an increasing recognition that there is now considerable difficulty in sending people to sites to perform time based preventative inspection or maintenance, (often proving to be of little actual value). This poses not just a threat to the person performing the inspection / maintenance, but also to other site-based staff.

The conclusion is there currently remains a significant level of misunderstanding of the perceived level of risk mitigation delivered by preventative inspection / maintenance, compared to the actual level delivered. New sensor technology now resolves this issue, and delivers a solution which not only provides Opex saving, and increased safety, but also avoids building in obsolescence to new build equipment by making it fully compatible with the requirements of digitization. Thus, an essential action for organizations adopting a digitization strategy is to replace thermal windows in electrical switchgear specifications, with thermal monitoring sensors, thereby avoiding building in obsolescence to new equipment, which would be a strategic investment mistake.

In addition, when scheduled maintenance shutdowns are planned, this provides the best opportunity to install thermal condition monitoring sensors, thereby upgrading the equipment and making it possible to obtain all the OPEX, safety, and increased uptime benefits, as well as inclusion in IIOT predictive analytics software programs, whilst effectively closing the ‘Performance Gap’ which exists with preventive maintenance.

Here's a quick takeaway for the Top 10 Reasons Why Sensor-Based Predictive Monitoring in Power Infrastructure is Crucial.

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