PD testing - preferences and references
PD testing - preferences and references
(OP)
Hello,
Partial Discharge testing in repair shops for motors and transformers is done in several different ways. Mostly RF based, but also Ultrasound and perhaps (never seen that) using ozone detection.
This is a broad question and all having any experience with PD testing and evaluation is invited to share their views and practises.
A few questions to start with:
1 When do you use PD testing?
2 For what objects?
3 At what levels?
4 What detectors do you use?
5 How do you evaluate your results?
6 Tips, tricks, traps?
Partial Discharge testing in repair shops for motors and transformers is done in several different ways. Mostly RF based, but also Ultrasound and perhaps (never seen that) using ozone detection.
This is a broad question and all having any experience with PD testing and evaluation is invited to share their views and practises.
A few questions to start with:
1 When do you use PD testing?
2 For what objects?
3 At what levels?
4 What detectors do you use?
5 How do you evaluate your results?
6 Tips, tricks, traps?
Gunnar Englund
www.gke.org





RE: PD testing - preferences and references
We have on occasion requested off-line partial discharge tests from our repair shops after rewind.
Our repair shops also use TVA probe to check for partial discharge activity in the slots.
I have used a Drager sampler with disposable tube to check for ozone on our motor's air exhausts in cases where they had high partial discharge indicated by the Iris equipment. Never saw enough to be detectable.
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RE: PD testing - preferences and references
http://www.irispower.com/newsite/index.aspx
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Eng-tips forums: The best place on the web for engineering discussions.
RE: PD testing - preferences and references
http://www.pdtech.ch/index1.php
RE: PD testing - preferences and references
To say that these tests ever saved one of my motors, I can't, but I believe that there is some value in PD testing motors in the long run. Question is, if the ability to get a unit out of service once every 4 to 8 years, do you trust a +/-Qm plot or do you just get it serviced?
electricpete: Do you have any info to support the value, or lack of, PD testing on 4 kV motors? I always thought that 4kV was a valid testing potential?
RE: PD testing - preferences and references
e.g.
Cast resin transformers
potential transformers
motors
pulse transformers for thyristor firing
transformers within IGBT-drivers
The PD test level is only slightly higher than the voltage during operation, but PD testing a device which has to withstand 1000 V with 1200 V provides much more reliability that doing highpot-test at several kV.
For details check the standards (e.g. IEC).
RE: PD testing - preferences and references
hours or days weeks after pd pattern is detected before failure is imminent (because pd does not occur at that voltage until insulation is very close to fully breached).
In contrast for 13.8kv machines you can have months or years.
So to be effective at the lower level, you need continuous monitoring/alarm (maybe that's what you have) in order to have time to react.
At higher voltage level you can do the walkaround checks and still get good benefit.
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RE: PD testing - preferences and references
You might like to explore this website a little. The man who runs it is a one-man-band consultant who specialises in large generating plant. He's done a lot of research into PD measurement on these large machines. And he's also a nice guy on top of that.
http://www.exon1.demon.co.uk/main.htm
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RE: PD testing - preferences and references
Thanks for the post. Currently we do not do continuous monitoring, but that is something to look into for the future. On my 5kV motors, I try to do semi-annual checks, winter and summer to get some idea of temperature variations on the equipment.