Partial Discharge
Partial Discharge
Introduction
Electrical systems are among the most valuable assets in your plant and can have the biggest impact on your bottom line. Their production and management cost is high and failures almost always lead to catastrophic losses. Electrical systems are being operated at higher levels, even while systems are aging -which affects both the life and the reliability of assets.
Today’s Asset Managers are facing the increased challenge of maximizing their aging electrical infrastructure with fewer qualified technical in-house resources, stricter regulatory requirements for worker safety, and shrinking maintenance budgets. Advances in technology, including the use of Partial Discharge Testing, are giving Asset Managers new approaches to achieve improved reliability and performance of critical electrical assets.
At Electest, we have many ways of detecting PD using both online and offline methods. We also carry out this test on the equipments as follow:
• Rotating Machine
– Offline and Online Measurement using Doble PD Smart & OMICRON MPD 600
• Transformer
– Online Acoustic & UHF Measurement using AE150-NDB, Doble PD Smart & OMICRON MPD 600
• Cable
– Online Measurement using HFCT with IPEC Longshot
– Offline Measurement using OWTS Seba MKT & Baur VLF PD
• HV Switchboard
– AIS & GIS using Online Measurement Techniques which include Acoustic, TEV, Ultrasonic, Corona, RFI & UHF
What is Partial Discharge?
Partial discharges are generally a result of local electrical stress concentrations in the insulation or on the surface of the insulation and are often accompanied by the emission of sound, light, heat, or chemical reactions. Partial discharges are small electrical sparks that occur within the insulation of medium and high voltage electrical assets. These discharges erode insulation and eventually result in insulation failure.
Partial Discharge types include:
- Void in solid insulation
- Cavity in liquid
- Electrical tree (void) around a sharp point
- Electrical floating potential
- Surface discharge
- Corona
Data obtained through Partial Discharge Testing and Monitoring can provide critical information on the quality of insulation and its impact on overall equipment health. Because partial discharge activity is often present well in advance of insulation failure, Asset Managers can monitor it over time and make informed strategic decisions regarding the repair or replacement of the equipment. These predictive diagnostics help companies to prioritise capital and MRO investments before an unexpected outage occurs. Partial discharge testing results can help predict future performance and reliability of critical assets, including:
- Cables, splices and terminations
- Power transformers and bushings
- Switchgear
- Motors and generators
Failures are not limited to service aged equipment. Acceptance testing on newly-installed equipment builds-in reliability right from start-up. Acceptance testing can:
- Verify original manufacturers test data and identify damaged
insulation that occurred from improper transportation/installation, poor design, and/or poor workmanship during or after installation.
- Identify premature failures and capture baseline data to trend asset health over the asset’s life cycle to ensure maximum ROI.
Conclusion
The partial discharge measurement is a suitable method to detect and localize imperfections in the high voltage insulation system and provides a procedure for quality assurance of electrical equipment.