Online Partial Discharge Testing

Arc Flash Online Partial Discharge Testing

Online Partial Discharge Testing

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Arc Flash Online Partial Discharge Testing

Electricity is arguably the most valuable resource we have in our modern society. Without electricity, most of the things we do and rely on on a daily basis wouldn’t be there.

Having an appreciation of the current status of assets within a power system is critical to ensuring reliability. This information is even more critical today given the demands put on our aging electric grid infrastructure. Partial Discharge (PD) detection is a critical tool in understanding the health of the dielectric and therefore the health of electrical assets. When performed online it offers a non-intrusive and non-destructive testing approach. NFPA 70B, Recommended Practice for Electrical Equipment Maintenance, states that insulation breakdown is the number one cause of electrical failures. In an electrical asset, partial discharges provide an early indication of dielectric irregularities that can lead to insulation breakdown. PD testing is the best tool to evaluate the health of any electrical insulation. Performing the PD measurement with the asset connected to and energized by the power system (online) offers:
    • Comprehensive analysis: Understand the true in-service condition (type and severity of defect while in service)
    • Convenient: Without service interruption and non-destructive
    • Flexible: Can be performed on any electric asset using a variety of sensors


Doble has over 30 years of experience employing online testing technology in assessing power
cables. Our database contains thousands of results on a wide variety of cable systems PILC,
PE, XLPE EPR and rubber insulation, all of which have been evaluated by our team of subject
matter experts. Benefits to the Doble Online Condition Assessment process include:

    • Evaluation of longer lengths of cable because of reduced signal attenuation due to acquisition of electrical PD signal at a lower frequency (16kHz to 30MHz).
    • Improved overall assessment of the cable as a result of proprietary noise rejection algorithms which permit the measurement to be performed at a lower frequency.
    • Accurate assessment of the status of the cable by a team of highly experienced engineers.
    • Clean data stream from Doble’s proprietary sensors, designed and manufactured in house,
      that offer greater sensitivity than commercially available alternatives.
    • Avoids costly outages and reduces the potential for damage resulting from switching transients and/or isolation from power system.
    • Comprehensive assessment of the entire cable system: cables, terminations, splices, and connected assets.


The Online PD Testing methodology encompasses the following:

    • Data acquisition is performed without taking an outage.
    • Online testing provides a true in-service assessment of the asset. This passive test approach eliminates risk of overstressing the dielectric system inducing further degradation.
    • Signal analysis and pattern recognition allows for identification of defect types and extent of degradation.
    • Doble’s online assessment process measures signals that result during partial discharge. The measured PD signals facilitate an estimation of future performance and ranks the entire
      cable system.
    • Evaluations are made at discrete locations between terminals. Since cables age at different rates along their lengths, it can isolate the more heavily aged parts of the cable.
When searching for a reliable electrical safety consultant, call us at 1-888-NFPA70E. You will find everything you need here to understand, learn, and implement in your company as laid out in the NFPA 70E.