Optical gas-density monitor for high voltage switching installation

摘要

A method of monitoring the density of the insulating gas in a high voltage switching installation employs a halogen lightsource in a monitor unit (5) together with an optical interference sensor (15) whose output signal striations are coupled via the fibre-optic system (3). The monitor (5) also houses a reference interferometer (45) whose output signals from a reference gas and those of the gas under test are connected via an optical switch (49) to a spectrograph (58) in which their mutual interference results in a Moire pattern registered by a CCD line sensor (59). The sensor (59) output appearing as a beat frequency resultant is evaluated by Fourier transform at the controller (55) to establish an index of gas density.