Emerson’s Jonathan Murray discussed partial discharge solutions at the 2017 Ovation Users Group conference. Unplanned electrical asset failures can halt production and amount to millions of dollars of associated costs. The IEEE and NFPA organizations identify Partial Discharge (PD), a breakdown of the assets insulation, as a leading cause of failure. Manufacturers are looking for ways of transitioning away from traditional periodic testing and integrating continuous PD monitoring systems into the Ovation system and achieving predictive maintenance capabilities.
Jonathan opened with a story of a failure of a single switchgear for Delta airlines costing $150 million in economic loss. Typical methods of maintaining assets are reactive, preventive and predictive. Moving toward predictive maintenance often means identifying and solving potential failures before they lead to loss.
Critical Asset Monitoring protects against the electrical balance of plant outside the generators. Critical Assets include switchgear, transformers, RMU’s, LV distribution panels, bus ducts (poly-phase & uni-phase), motor controllers, etc.
Thermal breakdown occurs because of overload, corrosion, loose electrical connections and improper mechanical racking. Traditional monitoring is done with visual inspections. IntelliSAW critical asset monitoring provides continuous monitoring for humidity and ambient temperatures.
Partial discharge occurs in medium and high voltage applications. PD is caused by lightning and voltage surges and insulation degradation. PD progresses over time. There are two types of PD—internal discharge and external/surface discharge. Manual PD testing is typically performed once per year. This testing is complex and expensive and requires significant expertise to perform and analyze the results of the tests.
With IntelliSAW continuous PD monitoring, ultrahigh frequency (UHF) detection is used to detect PD conditions. Mounting a IntelliSAW PD detectors takes about 20 minutes and needs to be done when equipment being monitored is powered down. Once the system is installed, the data show rate of deterioration over time and the severity of the deterioration. Jonathan showed an example of an oil filled transformer where the PD detector was installed inside the transformer. It’s important to look at the trend data over time. Another example is continuous monitoring on electrical bus ducts:
It’s better to spot problems earlier before they lead to dangerous failures.