Partial Discharge 5 Common Questions
Published 08 Mar 2021
Partial Discharge
An Introduction To The Causes & Effects Of PD
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Thanks to Mo Cowhig Managing Director at Northern Power Services Ltd for the permission to republish
1. What Is Partial Discharge?
Partial discharges (PD) are small, localised breakdowns in the insulation in HV equipment and cables. PD does not span the whole insulation, hence ‘partial’. PD activity is an indicator of issues inside and outside the insulation. Testing for PD activity provides an early warning of a potential insulation failure.
2. What Causes Partial Discharge?
PD can be caused by one or a combination of factors. Faults in the manufacture of the insulation, not apparent when new, can lead to PD after being put into service. Poor installation and maintenance can also lead to PD. Ageing and stresses over time, combined with environmental factors, can cause PD.
3. How Do We Detect Partial Discharge Activity?
Partial discharge can be classified into three types. PD can be external on the surface, internal to the insulation and where sharp protrusions lead to corona activity.
Each of these sources require different detection methods. PD activity leads to the generation of a range of different energy types including heat, audible sound, ultrasonic sound, radio waves and transient earth voltages.
By detecting these different energies, and eliminating background noise, we can detect the presence and severity of PD activity. We use special instruments to detect these energy types and in combination determine the presence of PD.
4. Why Survey For Partial Discharge?
The effects of PD can be highly detrimental to the insulation medium. PD changes the nature of the insulation which gets increasingly worse over time.
Left unchecked, the insulation can become unable to withstand the stress of high voltage and a complete failure occurs. This final breakdown is catastrophic causing large scale damage to equipment and a danger to personnel.
It is accepted that over 80% of sub-station failures are caused by PD. These failures are entirely preventable by regular surveying for PD.
5. Do I Need To Interrupt My Supply?
Different equipment require different methods. For the purpose of an initial PD survey the equipment needs to be energised, so no outage is required. If PD is detected a more in depth study may be required.
Introduction to Partial Discharge Training Course
NEW – Introduction to Partial Discharge
A one day training session, carried out at your site. The training is aimed at engineers, facility managers and anyone new to partial discharge.
Topics covered include:
- What is partial discharge
- Causes of partial discharge
- Why test for partial discharge
- Detection techniques
- Practical – use of a hand held detector
To Book Click Here
Northern Power Services Ltd is a UK based expert in condition assessment and monitoring of electrical infrastructure. They work closely with you as an integral part of your asset management plan.
For More Details Contact Information Below:
Maurice D Cowhig
Founder & Managing Director
[email protected]
Thorne & Derrick
Specialist Electrical Distributor
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