Temperature Monitoring Protects Low-Voltage Assets

Electrical generation and associated high-voltage (HV) assets are part of critical infrastructure and receive a good amount of attention and investment to keep them in top shape. What has been overlooked to a degree are low-voltage (LV) power distribution assets operating at 600 V and below. These are the switchgear, power distribution units and motor control centers present in virtually every industrial and commercial site.

 Jay GansonThe root failure mode for most types of LV assets can be predicted and even prevented by monitoring a leading indicator, which is unexpected temperature rise. Jay Ganson describes the anatomy of LV failures, and how proactive condition monitoring can avoid them in his article Temperature Monitoring Protects Low-Voltage Assets, in the June, 2019 issue of Power. He begins by describing what can go wrong.

Loose connections, improper contacts, and corrosion all reduce the current-carrying surface area, increasing heat buildup where contact remains. When this heat buildup exceeds the asset’s allowable temperature, larger breakdowns are set in motion. In the least critical case, an overtemperature condition simply melts through without damaging other elements. However, the affected phase is effectively disconnected, resulting in a single-phase loss downstream. Of greater concern is when excessive heat migrates into conductors, eventually creating insulation damage leading to a phase-to-phase or phase-to-ground short circuit.

Temperature is obviously a critical parameter to monitor, but what constitutes a “good” temperature compared to a “bad” one? Manual inspections, even with infrared (IR) test devices, are intermittent, expose technicians to hazards and don’t indicate trends or peak conditions well.

With these limitations in mind, continuous monitoring offers a superior solution. Continuous monitoring enables temperatures to be trended under all conditions, not just the electrical load and environmental conditions the day an inspection is performed. A continuous monitoring system can alarm if a high threshold is exceeded, and data from the system can be analyzed offline to evaluate equipment health over time.

Obtaining the temperature of energized equipment can be challenging due to the voltages involved. For this reason, wireless devices using SAW (surface acoustic wave) technology rated for the service and able to be retrofitted or installed on new equipment are ideal.

Emerson Automation Solutions has developed a portfolio of compact SAW-based sensors under the IntelliSAW brand, which are targeted specifically for the very challenging and dense LV asset environment. This technology employs Integrated Near-Field Coupling (iNFC) to address these applications. Signals transmit wirelessly via iNFC across an insulated gap, achieving the required isolation. The product is wireless and passive, so it requires no maintenance in the form of battery replacement, and it contains no electronic components in the energized compartment that could fail.

The IntelliSAW iNFC family of temperature sensors is the ideal method for continuous monitoring of low voltage critical asset hot-spots at locations such as busbars, lugs, and cables. For maximum flexibility, several form factors of sensors are available. Designers can choose from two sizes of bus clip-on sensors, two sizes of three-pole sensors fitting a variety of breaker and disconnect lugs, and a dual-cable version suitable for common parallel conductor configurations. Clip-on, cable tie, and bolt-mounted options facilitate installation in both new and retrofit applications.

Peace of mind is available for owner/operators of LV assets, and continuous monitoring is a superior solution compared to manual inspections. There is now a cost-effective, convenient, and safer way to implement continuous monitoring solutions in these assets utilizing wireless SAW-based systems. Asset owner/operators who do so can feel confident that they have done everything in their power to maximize uptime and reliability for their customers.

You can find more information like this and meet with other people looking at the same kinds of situations in the Emerson Exchange365 community. It’s a place where you can communicate and exchange information with experts and peers in all sorts of industries around the world. Look for the Condition Monitoring and IIoT Groups, and other specialty areas for suggestions and answers.