Mar 2013
Electricity Transmission
Oil-less DGA Sampling (Prospective Trial)
Mar 2013
National Grid Electricity System Operator
National Grid TO Innovation Team
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Innovation Funding Incentive
Gas Distribution Networks
According to theory, with the oil being exposed to a very large surface area membrane, the gas contained within the oil will transfer to the low concentration gas space on the far side of the membrane to achieve equilibrium. This process will be faster and more efficient with the greatest surface area profile. Ceramic membranes offer this property. It is expected the membranes will be formed from aluminium nitride and coated with a 5µm layer of various polymers. The choice of polymer is a major goal of this trial.

The final field device will be a steel cylinder containing a series of very strong aluminium nitride tubes which give a potential surface area for the oil to act on of some 20m2 or above.

The device will be designed to gently circulate oil to and from the same sample valve. The surrounding container (purged on delivery with argon) will begin to assimilate diagnostic gases from the oil. Diagnostic gas will be removed from the sampling system by syringe and analysed by a laboratory.

This is a prospective trial to test the effectiveness of direct oil-gas separation across high surface area ceramic membranes coated with hydrophilic membranes.

The aim is to prove the functionality of membrane extraction to be used on oil filled transmission assets where the oil content is of very low volume and successive sampling results in the requirement to top up.

The end of trial will deliver quantitative data concerning extraction efficiency and most suitable membranes to use in the construction of a field worthy sampling system.

It is expected that the trial will deliver as far as a proposed technical drawing of the field trial system, if not a working prototype to demonstrate the technology The second part of this work is to look at key molecular species which can identify winding faults, generated when copper in contact with oil pushes upwards to temperatures of 600 DegC and above.

Identifying a key marker species may assist in distinguishing transformers suffering from winding faults from those suffering from non-critical overheating faults such as core-frame circulating currents.