From the Rolls-Royce experimental archive: a quarter of a million communications from Rolls-Royce, 1906 to 1960's. Documents from the Sir Henry Royce Memorial Foundation (SHRMF).
Results of electrical breakdown tests on different cable samples.
| Identifier | WestWitteringFiles\S\March1928-May1928\ Scan158 | |
| Date | 2nd May 1928 guessed | |
| -5- Contd. Following the above examination the electrical breakdown tests were made. Each sample of cable (in each case the sample used was the one of its group which appeared by inspection to be the best) was placed with its central portion immersed in a tank of water at normal atmospheric temperature for 24 hours, sufficient length of ends being left projecting to prevent a breakdown along the surface. Whilst still immersed, the conductors were subjected to a high A.C. potential in relation to the tank, and the results were as follows :- (1) In case No.(1) the sample selected (Glover) broke down immediately on the pressure being raised to 18,000 volts R.M.S. (2) In case (2) the sample (Glover) withstood the available (at the time) pressure of 19,000 volts R.M.S. for 7 minutes, after which it broke down. The reason a pressure test of the Maconita cable from this same group was not made was that it was deemed unnecessary, as in all other pressure tests of Maconita no breakdown has occurred. (3) In the case of sample (3) (Maconite) this withstood the full available (at the time) pressure of 21,300 volts R.M.S. for 15 minutes satisfactorily. (4) In the case of sample (4) (Maconite) this withstood the full available (at the time) pressure of 19,000 volts R.M.S. for 15 minutes satisfactorily. (5) In the case of samples (5) (Maconite and Glover) both withstood the full available (at the time) voltage pressure of 19,000 volts R.M.S. for 15 minutes satisfactorily. From the above it will be noted that there is a distinct evidence of superiority in the Maconita cable. Contd. | ||