Evaluation of the performance of the impregnating resin of high voltage electrical machine when exposed to raw natural gas

Abstract

Future high-speed electrical motor technology will utilise wellstream hydrocarbon gas as cooling medium. Such integrated motor-compressors are currently under qualification for use on the sea floor in the North Sea. A vital part of the insulation system is the resin used to impregnate the motor windings and the resins ability to withstand chemical aging caused by the components inside the wellstream gas. The purpose of the resin in such a machine is to give mechanical support to the winding and to fill all gaps and voids inside the mainwall insulation, which consists of a mica paper tape. Various types of epoxy resins were exposed to an environment consisting of hydrocarbon gas, condensate and a mixture of water and monoethylene glycol (MEG). The specimens were built by casting the resin into a mould and curing it in an oven according to the procedure recommended by the resin manufacturers. According to the tests, the epoxy novolac and bisphenol A epoxy resin with BCl 3 accelerator were able to withstand their tensile strength and e-modulus during the exposure far better than the bisphenol F epoxy resin. The influence of an accelerator in an epoxy anhydride resin system was detected. Resins accelerated with zinc naphthenate provided the highest modulus before the tests, but were not able to retain it during the exposure. Resins accelerated with BCl 3 seemed to tolerate the environment better. The tensile strength of the resin was also dependent upon the amount of BCl 3 accelerator used.

Fortifying Subsea Wells: A Comparative Analysis of Mainwall Insulation Materials Used in Natural Gas Production

“…rr tapes contain epoxy novolac resin, which is usually more resistant to unfavorable environments than other resins. similar observations were made in [4], which was carried out for impregnating resins. the epoxy novolac resin in rr tapes is not, however, the one used in [4].…”

“…When exposed to the wellstream gas, the epoxy resin absorbs some gas, which is seen as a weight increase ( figure 4). In addition, the resin gets mechanically softer, which can be seen as a reduced e-modulus (figure 8), and the glass transition temperature of the resin decreases as a result of the diffusion of the gas mixture [4]. the adhesive strength of the resin is reduced, and an external force may cause it to detach from the glass strains.…”

“…It is reported in [15] that the tensile strength, e-modulus, and toughness of the insulation with polyesterimide resin decreased ~10% and the weight and volume increased by 50% when compared with the epoxy-based system. In [4], different impregnating resins were tested in raw natural gas. It was concluded that the epoxy novolac resin and bisphenol a epoxy resin with a BCl3 accelerator provided the best performance.…”