Partial Discharge
PD Causes and Effects
What’s a Partial Discharge?A Partial Discharge (PD) is an electrical discharge or spark that bridges a small portion of the insulation between two conducting electrodes.
PD can occur at any point in the insulation system, where the electric field strength exceeds the breakdown strength of that portion of the insulating material.
PD can occur in voids within solid insulation, across the surface of insulating material due to contaminants or irregularities, within gas bubbles in liquid insulation or around an electrode in gas (corona activity).
PD Emissions
Partial Discharges emit energy as:
- Electromagnetic emissions, in the form of radio waves, light and heat
- Acoustic emissions, in the audible and ultrasonic ranges
- Ozone and nitrous oxide gases
How PD activity leads to failure
PD activity provides clear evidence that an asset is deteriorating in a way that is likely to lead to failure.
The process of deterioration can propagate and develop, until the insulation is unable to withstand the electrical stress, leading to flashover.
The ultimate failure of HV/MV assets is often sudden and catastrophic, producing major damage and network outages.
PD Detection & Measurement Technologies
Transient Earth Voltages(TEVs) Measuring TEV emissions is a highly effective way of detecting, quantifying and locating PD activity in live assets.
The importance of TEV effects (discharges of radio energy associated with PD activity) was first identified by EA Technology in the 1970s and is the key to our technical leadership in PD detection and measurement.
TEV sensors are employed in all of our core PD instruments. This makes them far superior to products that only measure
ultrasonic emissions.
UltrasonicsPD activity creates emissions in both the audible and ultrasonic ranges. The latter is by far the most valuable for early detection and measurement.
All of our latest handheld PD instruments employ ultrasonic sensors, in addition to TEV sensors. This combination of technologies is unique in instruments of this size and versatility.
Most importantly, the trigger points on our instruments are precisely set to indicate critical PD activity, which is immediately apparent to the user, regardless of their level of expertise. No other handheld PD instruments on the market provide information of this accuracy and value.
PD Approach Video
The PD Approach film (below) uses live filming in substations plus advanced 3D graphics to ‘look inside’ switchgear and transformers and examine the causes and effects of PD. It also explains the latest tools and techniques available to detect, locate, measure, monitor, analyse and interpret PD activity.
Or alternatively watch our PD Podcast
http://www.eapodcasts.com/
Click here for more information on EA Technology Partial Discharge Instruments