Systems operate at DC voltages from 270V to over 800V (with
these bus voltages increasing during transient events). Components operating in
these DC systems are generally expected to be partial discharge free. However,
the estimation of the voltage at which a system will remain PD free is
difficult as it will be a function of the insulation conductivity (which can
vary significantly with temperature). Additionally, measurements of DC partial
discharge are challenging owing to the low frequency of discharges.
Guidance on the best methods to estimate DC partial
discharge performance and how to verify through test would be welcome. It would
ensure that electrical products being developed for use on the next generation
of aircraft would be designed at the optimal level of power density.
The project would seek to establish a method for DC partial discharge testing that delivers repeatable results across a range of environmental conditions and sample types.
A dedicated DC test bench would be established at aHV for use throughout the project period. This would allow DC PD testing to voltages of 10kV with an Omicron partial discharge detection system being used. Testing would be possible at reduced pressure and at elevated temperature.
Three forms of test method would be assessed: stepped DC voltage, ramped DC voltage and DC voltage with ripple (a recent paper suggesting that the testing with varying percentages of ripple can speed up the determination of DC PDIV). Testing would be carried out at a range of pressures and temperatures. Additional measurements of insulation conductivity would be made (where possible depending on sample type and availability of raw material) to try and correlate the DC PDIV results with the electrical conductivities being measured.
The comparative behaviour of the different test objects supplied for the study would be shared with all participants in a test report that would highlight the repeatability of each test method.
A DC test procedure would be drafted for circulation to relevant standards committees.
It is expected that this project would run for a 12 month period (given the volume of testing required and the relatively long duration of a single DC partial discharge test).
Our target timings for this project are as follows:
- Agreement of project scope - February
- Finalisation of project scope and costings - March
- Project kick-off - April
To date, we have
three companies who have expressed interest in this project so are seeking no more than one or two other partners.
If you would like to receive more details of this project, please contact
h.jahangiri@aerospacehv.com
